nih-gov/medlineplus.gov/lab-tests/osmolality-tests/index.html
2025-02-26 13:17:41 -05:00

708 lines
44 KiB
HTML
Raw Permalink Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<!DOCTYPE html>
<html lang="en" id="lab_test" class="nojs us" data-root="https://medlineplus.gov/">
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
<meta http-equiv="window-target" content="_top" />
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<link rel="canonical" href="https://medlineplus.gov/lab-tests/osmolality-tests/" />
<link rel="alternate" hreflang="en" href="https://medlineplus.gov/lab-tests/osmolality-tests/" />
<link rel="alternate" hreflang="es" href="https://medlineplus.gov/spanish/pruebas-de-laboratorio/pruebas-de-osmolalidad/" />
<meta name="ac-dictionary" content="medlineplus-ac-dictionary" />
<meta name="description" content="Osmolality tests measure the amount of certain electrolytes and chemicals in your blood, urine, or stool. These tests check your body&#x27;s fluid balance. Learn more." />
<link rel="shortcut icon" href="https://medlineplus.gov/images/favicon.ico" type="image/x-icon" />
<link rel="apple-touch-icon" href="https://medlineplus.gov/images/touch-icon.png" />
<meta property="fb:app_id" content="1042245625821448" />
<meta property="og:title" content="Osmolality Tests: MedlinePlus Medical Test" />
<meta property="og:url" content="https://medlineplus.gov/lab-tests/osmolality-tests/" />
<meta property="og:image" content="https://medlineplus.gov/images/LabTests_Share.jpg" />
<meta property="og:image" content="https://medlineplus.gov/images/LabTest_Share2.jpg" />
<meta property="og:image" content="https://medlineplus.gov/images/LabTests_Share3.jpg" />
<meta property="og:description" content="Osmolality tests measure the amount of certain electrolytes and chemicals in your blood, urine, or stool. These tests check your body&#x27;s fluid balance. Learn more." />
<meta name="twitter:card" content="summary_large_image" />
<meta name="twitter:site" content="@medlineplus" />
<meta name="twitter:creator" content="@medlineplus" />
<meta name="twitter:title" content="Osmolality Tests: MedlinePlus Medical Test" />
<meta name="twitter:description" content="Osmolality tests measure the amount of certain electrolytes and chemicals in your blood, urine, or stool. These tests check your body&#x27;s fluid balance. Learn more." />
<meta name="twitter:image" content="https://medlineplus.gov/images/LabTests_Share.jpg" />
<meta name="twitter:image:alt" content=""/>
<meta property="og:image:alt" content="" />
<title>Osmolality Tests: MedlinePlus Medical Test</title>
<link rel="stylesheet" href="https://medlineplus.gov/css/common_new.css?1738957219841" />
<!--[if IE 8]> <link rel="stylesheet" href="https://medlineplus.gov/css/ie8/common.css"> <![endif]-->
<link rel="stylesheet" href="https://medlineplus.gov/uswds/css/uswds_styles.css" />
<script type="text/javascript">document.getElementsByTagName('html')[0].className = document.getElementsByTagName('html')[0].className.replace( /(?:^|\s)nojs(?!\S)/g , '').trim();</script>
<script src="https://medlineplus.gov/uswds/js/uswds-init.min.js" type="text/javascript"></script>
<script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
})(window,document,'script','dataLayer','GTM-MMVM77');</script>
</head>
<body>
<noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-MMVM77"
height="0" width="0" style="display:none;visibility:hidden" title="googletagmanager"></iframe></noscript>
<a name="top" id="top"></a>
<a class="hide-offscreen" href="#start">Skip navigation</a>
<section
class="usa-banner"
aria-label="Official website of the United States government"
>
<div class="usa-accordion">
<header class="usa-banner__header">
<div class="usa-banner__inner">
<div class="grid-col-auto">
<img
aria-hidden="true"
class="usa-banner__header-flag"
src="https://medlineplus.gov/uswds/img/us_flag_small.png"
alt=""
/>
</div>
<div class="grid-col-fill tablet:grid-col-auto" aria-hidden="true">
<p class="usa-banner__header-text">
An official website of the United States government
</p>
<p class="usa-banner__header-action">Heres how you know</p>
</div>
<button
type="button"
class="usa-accordion__button usa-banner__button"
aria-expanded="false"
aria-controls="gov-banner-default-default"
>
<span class="usa-banner__button-text">Heres how you know</span>
</button>
</div>
</header>
<div
class="usa-banner__content usa-accordion__content"
id="gov-banner-default-default"
>
<div class="grid-row grid-gap-lg">
<div class="usa-banner__guidance tablet:grid-col-6">
<img
class="usa-banner__icon usa-media-block__img"
src="https://medlineplus.gov/uswds/img/icon-dot-gov.svg"
role="img"
alt=""
aria-hidden="true"
/>
<div class="usa-media-block__body">
<p>
<strong>Official websites use .gov</strong><br />A
<strong>.gov</strong> website belongs to an official government
organization in the United States.
</p>
</div>
</div>
<div class="usa-banner__guidance tablet:grid-col-6">
<img
class="usa-banner__icon usa-media-block__img"
src="https://medlineplus.gov/uswds/img/icon-https.svg"
role="img"
alt=""
aria-hidden="true"
/>
<div class="usa-media-block__body">
<p>
<strong>Secure .gov websites use HTTPS</strong><br />A
<strong>lock</strong> (
<span class="icon-lock"
><svg
xmlns="http://www.w3.org/2000/svg"
width="52"
height="64"
viewBox="0 0 52 64"
class="usa-banner__lock-image"
role="img"
aria-labelledby="banner-lock-description-default"
focusable="false"
>
<title id="banner-lock-title-default">Lock</title>
<desc id="banner-lock-description-default">Locked padlock icon</desc>
<path
fill="#000000"
fill-rule="evenodd"
d="M26 0c10.493 0 19 8.507 19 19v9h3a4 4 0 0 1 4 4v28a4 4 0 0 1-4 4H4a4 4 0 0 1-4-4V32a4 4 0 0 1 4-4h3v-9C7 8.507 15.507 0 26 0zm0 8c-5.979 0-10.843 4.77-10.996 10.712L15 19v9h22v-9c0-6.075-4.925-11-11-11z"
/>
</svg> </span
>) or <strong>https://</strong> means youve safely connected to
the .gov website. Share sensitive information only on official,
secure websites.
</p>
</div>
</div>
</div>
</div>
</div>
</section>
<div id="mplus-wrap">
<header>
<div id="mplus-header">
<div id="mplus-orgs">
<a href="https://www.nih.gov/" class="nih-org" target="_blank" title="National Institutes of Health">
<img class="nihlogo" src="https://medlineplus.gov/images/nihlogo.png" alt="National Institutes of Health"/>
</a><a href="https://www.nlm.nih.gov/" target="_blank"> National Library of Medicine</a>
</div>
<div id="mplus-logo" class="years-25">
<a href="https://medlineplus.gov/">
<img alt="MedlinePlus Trusted Health Information for You" title="MedlinePlus Trusted Health Information for You" src="https://medlineplus.gov/images/m_logo_25.png"/>
</a>
</div>
<div id="mplus-nav">
<div aria-live="polite" class="sm-live-area hide-offscreen"></div>
<button id="sm-menu-btn" class="navmenu-btn" title="Menu" role="button" aria-controls="mplus-menu-list" type="submit">Menu<span class="icon icon-nav-menu"></span></button>
<ul id="mplus-menu-list" class="nav-list">
<li><a href="https://medlineplus.gov/healthtopics.html">Health Topics</a></li>
<li><a href="https://medlineplus.gov/druginformation.html">Drugs & Supplements</a></li>
<li><a href="https://medlineplus.gov/genetics/">Genetics</a></li>
<li><a href="https://medlineplus.gov/lab-tests/">Medical Tests</a></li>
<li><a href="https://medlineplus.gov/encyclopedia.html">Medical Encyclopedia</a></li>
<li><a href="https://medlineplus.gov/about/">About MedlinePlus</a></li>
</ul><button id="sm-search-btn" class="navmenu-btn" title="Search" role="button" aria-controls="mplus-search" type="submit"><span class="hide-offscreen"></span>Search<span class="icon icon-nav-search"></span></button>
<div class="top-1">
<form id="mplus-search" method="get" action="https://vsearch.nlm.nih.gov/vivisimo/cgi-bin/query-meta" title="Search MedlinePlus" target="_self">
<input type="hidden" name="v:project" value="medlineplus"/>
<input type="hidden" name="v:sources" value="medlineplus-bundle"/>
<div class="form-box text-combo">
<div class="form-area"><label class="hide-offscreen" for="searchtext_primary">Search MedlinePlus</label>
<input id="searchtext_primary" class="form-text" type="text" placeholder="Search MedlinePlus" alt="#Site Search input" title="Site Search input" maxlength="400" size="40" name="query" autocomplete="off" role="textbox" aria-autocomplete="list" aria-haspopup="true"/>
</div>
<div class="button-area">
<button class="form-btn" title="Search MedlinePlus" alt="Search MedlinePlus" type="submit">GO</button>
</div>
</div>
</form>
<div class="secondarynav">
<ul class="nav-list">
<li><a href="https://medlineplus.gov/about/"><span>About MedlinePlus</span></a></li>
<li><a href="https://medlineplus.gov/whatsnew/">What's New</a></li>
<li><a href="https://medlineplus.gov/sitemap.html"><span>Site Map</span></a></li>
<li><a href="https://support.nlm.nih.gov/knowledgebase/category/?id=CAT-01231&category=medlineplus&from=https%3A//medlineplus.gov/lab-tests/osmolality-tests/" target="_blank"><span>Customer Support</span></a></li>
</ul>
</div>
</div>
<div id="mplus-nav-bar">
<ul class="nav-list">
<li><a href="https://medlineplus.gov/healthtopics.html">Health Topics</a></li><li><a href="https://medlineplus.gov/druginformation.html">Drugs & Supplements</a></li><li><a href="https://medlineplus.gov/genetics/">Genetics</a></li><li><a href="https://medlineplus.gov/lab-tests/">Medical Tests</a></li><li><a href="https://medlineplus.gov/encyclopedia.html">Medical Encyclopedia</a></li>
</ul>
</div>
<a id="mplus-lang-toggle" href="https://medlineplus.gov/spanish/pruebas-de-laboratorio/pruebas-de-osmolalidad/" title="Español">Español</a>
</div>
</div>
</header>
<div id="mplus-content">
<div id="breadcrumbs">
<div itemprop="breadcrumb" itemscope="" itemtype="http://schema.org/BreadcrumbList">
<span class="hide-offscreen">You Are Here:</span>
<div itemscope itemprop="itemListElement" itemtype="http://schema.org/ListItem">
<a href="https://medlineplus.gov/" itemprop="item"><span itemprop="name">Home</span></a>
&rarr;
<meta itemprop="position" content="1"/>
</div>
<div itemscope itemprop="itemListElement" itemtype="http://schema.org/ListItem">
<a href="https://medlineplus.gov/lab-tests/" itemprop="item"><span itemprop="name">Medical Tests</span></a>
&rarr;
<meta itemprop="position" content="2"/>
</div>
<div>
<span>Osmolality Tests</span>
</div>
</div>
</div>
<span class="page-url print-only">URL of this page: https://medlineplus.gov/lab-tests/osmolality-tests/</span>
<div >
<article>
<div class="page-info">
<div class="page-title">
<a name="start" id="start"></a>
<h1>Osmolality Tests</h1>
</div>
<div class="page-actions"></div>
<noscript><span class="js-disabled-message">To use the sharing features on this page, please enable JavaScript.</span></noscript>
</div>
<div class="main">
<section><div class="mp-content"><h2>What are osmolality tests?</h2>
<p>Osmolality tests measure the amount of certain substances in your blood, urine, or stool (poop). The tests can show how your kidneys are working and whether you have an unhealthy <a data-tid="4224" href="https://medlineplus.gov/fluidandelectrolytebalance.html">fluid balance</a>.</p>
<p>The substances that the tests measure include:</p>
<ul>
<li><a data-pid="690" href="https://medlineplus.gov/lab-tests/blood-glucose-test/">Glucose</a> (sugar).</li>
<li>Urea (a waste product made in the liver).</li>
<li>Several electrolytes, such as <a data-pid="714" href="https://medlineplus.gov/lab-tests/sodium-blood-test/">sodium</a>, <a data-pid="676" href="https://medlineplus.gov/lab-tests/potassium-blood-test/">potassium</a>, and <a data-pid="736" href="https://medlineplus.gov/lab-tests/chloride-blood-test/">chloride</a>. Electrolytes are <a data-tid="4298" href="https://medlineplus.gov/minerals.html">minerals</a> that have an electrical charge when they are dissolved in water or body fluids. They help control the balance of fluids in the body. They also help balance the acids and bases (pH balance) in your body.</li>
</ul>
<p>Osmolality is the concentration of particles dissolved in your body fluid. The concentration is based on the amount of particles that are in a specific amount of that fluid. Different factors can make it go up or down:</p>
<ul>
<li>Your blood osmolality increases when the amount of water in your blood decreases or the number of substances such as sodium, chloride, and glucose increases. When your blood osmolality goes up it causes your kidney to hold onto water. This makes your urine more concentrated.</li>
<li>Your blood osmolality decreases when the amount of water in your blood increases. This makes your urine more diluted.</li>
</ul>
<p>This process helps your body maintain a healthy fluid balance. But sometimes this balance can be thrown off. Many different conditions and factors can cause an unhealthy fluid balance, such as. too much salt intake, <a data-tid="91" href="https://medlineplus.gov/kidneydiseases.html">kidney disease</a>,<a data-tid="277" href="https://medlineplus.gov/heartdiseases.html"> heart disease</a>, and some types of <a data-tid="364" href="https://medlineplus.gov/poisoning.html">poisoning</a>.</p>
<p>Other names: serum osmolality, plasma osmolality, urine osmolality, stool osmolality, osmotic gap</p></div>
</section>
<section><div class="mp-content"><h2>What are they used for?</h2>
<p>Osmolality tests may be used for a variety of reasons. <strong>A blood osmolality test</strong>, also known as a serum osmolality test, is most often used to:</p>
<ul>
<li>Check the balance between water and certain substances in your blood.</li>
<li>Find out if you have swallowed a poison such as antifreeze or rubbing alcohol.</li>
<li>Check for an overdose of drugs such as <a data-pid="14107" href="https://medlineplus.gov/lab-tests/salicylates-level/">salicylates</a>, commonly found in aspirin.</li>
<li>Help diagnose <a data-tid="6051" href="https://medlineplus.gov/dehydration.html">dehydration</a>, a condition in which your body loses too much fluid.</li>
<li>Help diagnose overhydration, a condition in which your body retains (holds in) too much fluid.</li>
<li>Help diagnose <a data-tid="3046" href="https://medlineplus.gov/diabetesinsipidus.html">diabetes insipidus</a>, a condition that affects the kidneys. It causes frequent urination, which can lead to dehydration.</li>
</ul>
<p>Sometimes, your blood plasma is also tested for osmolality by measuring the amount of sodium dissolved in it.</p>
<p><strong>A urine osmolality test</strong> is often used along with a serum osmolality test to check your body's fluid balance. The urine test may also be used to find out the reason for increased or decreased urination.</p>
<p><strong>A stool osmolality test</strong> is most often used to find out the reason for chronic <a data-tid="211" href="https://medlineplus.gov/diarrhea.html">diarrhea</a> that is not caused by a <a data-tid="158" href="https://medlineplus.gov/bacterialinfections.html">bacterial</a> or <a data-tid="482" href="https://medlineplus.gov/parasiticdiseases.html">parasitic</a> infection.</p></div>
</section>
<section><div class="mp-content"><h2>Why do I need an osmolality test?</h2>
<p>You may need a serum osmolality or urine osmolality test if you have symptoms of a fluid imbalance, diabetes insipidus, or certain types of poisoning.</p>
<p>Symptoms of a fluid imbalance and diabetes insipidus are similar and may include:</p>
<ul>
<li>Excessive thirst (if dehydrated)</li>
<li><a data-tid="489" href="https://medlineplus.gov/nauseaandvomiting.html">Nausea and vomiting</a></li>
<li><a data-tid="273" href="https://medlineplus.gov/headache.html">Headache</a></li>
<li>Confusion</li>
<li><a data-tid="5324" href="https://medlineplus.gov/fatigue.html">Fatigue</a></li>
<li><a data-tid="396" href="https://medlineplus.gov/seizures.html">Seizures</a></li>
</ul>
<p>Symptoms of poisoning will be different depending on the type of substance that was swallowed but may include:</p>
<ul>
<li>Nausea and vomiting</li>
<li>Convulsions, a condition that causes uncontrollable shaking of your muscles</li>
<li><a data-tid="3077" href="https://medlineplus.gov/breathingproblems.html">Trouble breathing</a></li>
<li>Slurred speech</li>
</ul>
<p>You may also need a urine osmolality test if you have trouble urinating or are urinating too much. This test measures how well your kidneys are working.</p>
<p>You may need a stool osmolality test if you have chronic diarrhea that can't be explained by a bacterial or parasitic infection or another cause such as intestinal damage.</p></div>
</section>
<section><div class="mp-content"><h2>What happens during an osmolality test?</h2>
<p><strong>During a blood test</strong> (serum osmolality or plasma osmolality):</p>
<p>A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.</p>
<p><strong>During a urine osmolality test:</strong></p>
<p>You will need to give a urine sample for the test. A health care professional may give you a cleansing wipe, a small container, and instructions for how to use the "clean catch" method to collect your urine sample. It's important to follow these instructions so that germs from your skin don't get into the sample:</p>
<ol>
<li>Wash your hands with soap and water and dry them.</li>
<li>Open the container without touching the inside.</li>
<li>Clean your genital area with the cleansing wipe.
<ul>
<li>For a penis, wipe the entire head (end) of the penis. If you have a foreskin, pull it back first.</li>
<li>For a vagina, separate the labia (the folds of skin around the vagina) and wipe the inner sides from front to back.</li>
</ul>
</li>
<li>Urinate into the toilet for a few seconds and then stop the flow. Start urinating again, this time into the container. Don't let the container touch your body.</li>
<li>Collect at least an ounce or two of urine into the container. The container should have markings to show how much urine is needed.</li>
<li>Finish urinating into the toilet.</li>
<li>Put the cap on the container and return it as instructed.</li>
</ol>
<p>If you have hemorrhoids that bleed or are having your menstrual period, tell your provider before your test.</p>
<p><strong>During a stool osmolality test:</strong></p>
<p>You will need to provide a fresh sample of loose or liquid stool for your test. Your provider will probably give you a container or kit with instructions on how to collect the sample. There are different ways to collect stool samples so follow the instructions carefully. In general, you'll need to:</p>
<ul>
<li>Label the container with your name, the collection date, and time.</li>
<li>Collect a stool sample as instructed. This usually involves using a clean, dry container, or special paper or plastic wrap placed over the toilet to catch the stool.</li>
<li>Make sure the stool doesn't mix with any urine, toilet paper, or water from the toilet.</li>
<li>Close the container tightly.</li>
<li>Wash your hands well with soap and water.</li>
<li>Return the container according to the instructions. This is important to get an accurate test result.</li>
</ul>
<p>If you're collecting a sample from diapers, you'll get special instructions for using plastic wrap inside of a clean diaper. In certain cases, a provider may use a swab to take a stool sample from the rectum.</p></div>
</section>
<section><div class="mp-content"><h2>Will I need to do anything to prepare for the test?</h2>
<p>You may need to <a data-pid="858" href="https://medlineplus.gov/lab-tests/fasting-for-a-blood-test/">fast</a> (not eat or drink) for 6 hours before the test or limit fluids 12 to 14 hours before the test. Your provider will let you know if there are any special instructions to follow.</p></div>
</section>
<section><div class="mp-content"><h2>Are there any risks to osmolality tests?</h2>
<p>There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.</p>
<p>There is no risk to having a urine or stool test.</p></div>
</section>
<section><div class="mp-content"><h2>What do the results mean?</h2>
<p>If your <strong>serum osmolality</strong> results were not normal, it may be a sign of:</p>
<ul>
<li>Dehydration or overhydration</li>
<li>Too much or too little salt in the blood</li>
<li>Antifreeze or other types of poisoning</li>
<li>Diabetes insipidus</li>
<li><a data-tid="8" href="https://medlineplus.gov/stroke.html">Stroke</a></li>
</ul>
<p>If your <strong>urine osmolality</strong> results were not normal, it may be a sign of:</p>
<ul>
<li>Dehydration or overhydration</li>
<li><a data-tid="199" href="https://medlineplus.gov/heartfailure.html">Heart failure</a></li>
<li><a data-tid="310" href="https://medlineplus.gov/liverdiseases.html">Liver disease</a></li>
<li>Kidney disease</li>
</ul>
<p>If your <strong>stool osmolality</strong> results were not normal, it may be a sign of:</p>
<ul>
<li>Factitious diarrhea, a condition caused by the overuse of laxatives</li>
<li><a data-tid="5459" href="https://medlineplus.gov/malabsorptionsyndromes.html">Malabsorption</a>, a condition that affects your ability to digest and take in nutrients from food</li>
</ul>
<p>If you have questions about your results, talk to your provider. To understand the results of an osmolality test, your provider may consider your symptoms, medical history, and the results of other blood tests.</p>
<p>Learn more about <a data-pid="806" href="https://medlineplus.gov/lab-tests/how-to-understand-your-lab-results/">laboratory tests, reference ranges, and understanding results</a>.</p></div>
</section>
<section><div class="mp-content"><h2>Is there anything else I need to know about osmolality tests?</h2>
<p>Your provider may order more tests along with or after your osmolality test. These may include:</p>
<ul>
<li><a data-pid="728" href="https://medlineplus.gov/lab-tests/complete-blood-count-cbc/">Complete blood count (CBC)</a></li>
<li><a data-pid="730" href="https://medlineplus.gov/lab-tests/bun-blood-urea-nitrogen/">Blood urea nitrogen (BUN) test</a></li>
<li>Blood glucose test</li>
<li><a data-pid="10301" href="https://medlineplus.gov/lab-tests/electrolyte-panel/">Electrolyte panel</a></li>
<li><a data-pid="664" href="https://medlineplus.gov/lab-tests/albumin-blood-test/">Albumin blood test</a></li>
<li><a data-pid="746" href="https://medlineplus.gov/lab-tests/fecal-occult-blood-test-fobt/">Fecal occult blood test (FOBT)</a></li>
</ul></div>
</section>
<section><div class="mp-refs mp-content"><h2>References</h2>
<ol>
<li>Cleveland Clinic: Health Library: Diagnostics &amp; Testing [Internet]. Cleveland (OH): Cleveland Clinic; c2023. Blood Tests; [reviewed 2022 Dec 06; cited 2024 Mar 19]; [about 16 screens]. Available from: <a href="https://my.clevelandclinic.org/health/diagnostics/24508-blood-tests" target="bibliowin">https://my.clevelandclinic.org/health/diagnostics/24508-blood-tests</a></li>
<li>Cleveland Clinic: Health Library: Diagnostics &amp; Testing [Internet]. Cleveland (OH): Cleveland Clinic; c2023.Electrolyte Panel; [reviewed 2022 Feb 07; cited 2024 Mar 19]; [about 9 screens]. Available from: <a href="https://my.clevelandclinic.org/health/diagnostics/22358-electrolyte-panel" target="bibliowin">https://my.clevelandclinic.org/health/diagnostics/22358-electrolyte-panel</a></li>
<li>Guandalini, S. Microvillus Inclusion Disease Workup. [updated 2017 Oct 06; cited 2024 Mar 19]. In Medscape: Drugs &amp; Diseases: Pediatrics: General Medicine. [Internet]. Atlanta (GA): WebMD LLC; c1994-2022. Available from: <a href="https://emedicine.medscape.com/article/928100-workup#showall" target="bibliowin">https://emedicine.medscape.com/article/928100-workup#showall</a></li>
<li>Labcorp [Internet]. Burlington (NC): Laboratory Corporation of America(r) Holdings; c2023. Patient Test Information: Osmolality; [cited 2024 Mar 19]; [about 3 screens]. Available from: <a href="https://www.labcorp.com/tests/120071/osmolality-fecal" target="bibliowin">https://www.labcorp.com/tests/120071/osmolality-fecal</a></li>
<li>Labcorp [Internet]. Burlington (NC): Laboratory Corporation of America(r) Holdings; c2023. Patient Test Information: Osmolality; [cited 2024 Mar 19]; [about 3 screens]. Available from: <a href="https://www.labcorp.com/tests/002071/osmolality" target="bibliowin">https://www.labcorp.com/tests/002071/osmolality</a></li>
<li>LOINC [Internet]. Regenstrief Institute, Inc.; c1994-2024. Osmolality of Serum or Plasma; [cited 2024 Feb 28]; [about 3 screens]. Available from: <a href="https://loinc.org/2692-2" target="bibliowin">https://loinc.org/2692-2</a></li>
<li>Mayo Clinic Laboratories [Internet]. Mayo Foundation for Medical Education and Research; c1995-2024. Test ID: CPAVP: Copeptin proAVP, Plasma: Clinical and Interpretive; [cited 2024 Feb 28]; [about 3 screens]. Available from: <a href="https://www.mayocliniclabs.com/test-catalog/overview/603599#Clinical-and-Interpretive" target="bibliowin">https://www.mayocliniclabs.com/test-catalog/overview/603599#Clinical-and-Interpretive</a></li>
<li>Mayo Clinic Laboratories [Internet]. Mayo Foundation for Medical Education and Research; c1995-2024. Test ID: CPAVP: Copeptin proAVP, Plasma: Specimen; [cited 2024 Feb 28]; [about 2 screens]. Available from: <a href="https://www.mayocliniclabs.com/test-catalog/overview/603599#Specimen" target="bibliowin">https://www.mayocliniclabs.com/test-catalog/overview/603599#Specimen</a></li>
<li>Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck &amp; Co., Inc.; c2024. Overhydration; [modified 2022 Sep; cited 2024 Feb 28]; [about 3 screens]. Available from: <a href="https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/water-balance/overhydration" target="bibliowin">https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/water-balance/overhydration</a></li>
<li>Najem O, Shah MM, De Jesus O. Serum Osmolality. [Updated 2022 Dec 16; cited 2024 Mar 19]. [about 6 screens]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: <a href="https://www.ncbi.nlm.nih.gov/books/NBK567764/" target="bibliowin">https://www.ncbi.nlm.nih.gov/books/NBK567764/</a></li>
<li>National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; NCI Dictionary of Cancer Terms: plasma; [cited 2024 Feb 28]; [about 1 screens]. Available from: <a href="https://www.cancer.gov/publications/dictionaries/cancer-terms/def/plasma" target="bibliowin">https://www.cancer.gov/publications/dictionaries/cancer-terms/def/plasma</a></li>
<li>National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; NCI Dictionary of Cancer Terms: serum; [cited 2024 Feb 28]; [about 1 screens]. Available from: <a href="https://www.cancer.gov/publications/dictionaries/cancer-terms/def/serum" target="bibliowin">https://www.cancer.gov/publications/dictionaries/cancer-terms/def/serum</a></li>
<li>Nemours KidsHealth [Internet]. Jacksonville (FL): The Nemours Foundation; c1995-2023. Getting a Blood Test; [reviewed 2021 Sep; cited 2024 Mar 19]; [about 4 screens]. Available from: <a href="https://kidshealth.org/en/parents/blood-tests.html" target="bibliowin">https://kidshealth.org/en/parents/blood-tests.html</a></li>
<li>Pathology Tests Explained [Internet]. Alexandria (Australia): Australasian Association for Clinical Biochemistry and Laboratory Medicine; c2023. Osmolality; [reviewed 2023 Jun 1; cited 2024 Mar 19]; [about 5 screens]. Available from: <a href="https://pathologytestsexplained.org.au/ptests-pro.php?q=Osmolality" target="bibliowin">https://pathologytestsexplained.org.au/ptests-pro.php?q=Osmolality</a></li>
<li>Testing.com [Internet]. Seattle (WA): OneCare Media; c2024. Blood Urea Nitrogen (BUN) Test; [modified 2022 Nov 29; cited 2024 Feb 28]; [about 9 screens]. Available from: <a href="https://www.testing.com/tests/blood-urea-nitrogen-bun/" target="bibliowin">https://www.testing.com/tests/blood-urea-nitrogen-bun/</a></li>
<li>Testing.com [Internet]. Seattle (WA): OneCare Media; c2024. Electrolytes and Anion Gap Test; [modified 2022 Nov 29; cited 2024 Mar 20]; [about 12 screens]. Available from: <a href="https://www.testing.com/tests/electrolytes-and-anion-gap/" target="bibliowin">https://www.testing.com/tests/electrolytes-and-anion-gap/</a></li>
<li>Testing.com [Internet]. Seattle (WA): OneCare Media; c2024. Osmolality and Osmolal Gap; [modified 2021 Nov 9; cited 2024 Feb 28]; [about 9 screens]. Available from: <a href="https://www.testing.com/tests/osmolality-and-osmolal-gap/" target="bibliowin">https://www.testing.com/tests/osmolality-and-osmolal-gap/</a></li>
</ol></div>
</section>
</div>
<div class="side">
<aside>
<section><div class="side-section">
<div class="section-header">
<h2>Related Health Topics</h2>
</div>
<div class="section-body">
<ul class="relatedmp">
<li><a href="https://medlineplus.gov/dehydration.html">Dehydration</a></li>
<li><a href="https://medlineplus.gov/diabetesinsipidus.html">Diabetes Insipidus</a></li>
<li><a href="https://medlineplus.gov/diarrhea.html">Diarrhea</a></li>
<li><a href="https://medlineplus.gov/fluidandelectrolytebalance.html">Fluid and Electrolyte Balance</a></li>
<li><a href="https://medlineplus.gov/minerals.html">Minerals</a></li>
<li><a href="https://medlineplus.gov/poisoning.html">Poisoning</a></li>
<li><a href="https://medlineplus.gov/sodium.html">Sodium</a></li>
</ul>
</div>
</div></section>
<section><div class="side-section">
<div class="section-header">
<h2>Related Medical Tests</h2>
</div>
<div class="section-body">
<ul class="relatedmp">
<li><a href="https://medlineplus.gov/lab-tests/albumin-blood-test/">Albumin Blood Test</a></li>
<li><a href="https://medlineplus.gov/lab-tests/blood-glucose-test/">Blood Glucose Test</a></li>
<li><a href="https://medlineplus.gov/lab-tests/bun-blood-urea-nitrogen/">BUN (Blood Urea Nitrogen)</a></li>
<li><a href="https://medlineplus.gov/lab-tests/chloride-blood-test/">Chloride Blood Test</a></li>
<li><a href="https://medlineplus.gov/lab-tests/complete-blood-count-cbc/">Complete Blood Count (CBC)</a></li>
<li><a href="https://medlineplus.gov/lab-tests/electrolyte-panel/">Electrolyte Panel</a></li>
<li><a href="https://medlineplus.gov/lab-tests/fecal-occult-blood-test-fobt/">Fecal Occult Blood Test (FOBT)</a></li>
<li><a href="https://medlineplus.gov/lab-tests/how-to-cope-with-medical-test-anxiety/">How to Cope with Medical Test Anxiety</a></li>
<li><a href="https://medlineplus.gov/lab-tests/how-to-prepare-for-a-lab-test/">How to Prepare for a Lab Test</a></li>
<li><a href="https://medlineplus.gov/lab-tests/how-to-understand-your-lab-results/">How to Understand Your Lab Results</a></li>
<li><a href="https://medlineplus.gov/lab-tests/potassium-blood-test/">Potassium Blood Test</a></li>
<li><a href="https://medlineplus.gov/lab-tests/salicylates-level/">Salicylates Level</a></li>
<li><a href="https://medlineplus.gov/lab-tests/sodium-blood-test/">Sodium Blood Test</a></li>
<li><a href="https://medlineplus.gov/lab-tests/what-you-need-to-know-about-blood-testing/">What You Need to Know About Blood Testing</a></li>
</ul>
</div>
</div></section>
</aside>
</div>
<div class="bottom">
<section><div class="lt-disclaimer">
<p>The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.</p>
</div>
</section>
</div>
</article>
</div>
<div id="citation-how-to">
<button><span>Learn how to cite this page</span></button>
</div>
</div>
<footer>
<div id="mplus-footer">
<div class="footer1">
<ul class="secondarynav">
<li><a href="https://medlineplus.gov/about/">About MedlinePlus</a></li>
<li><a href="https://medlineplus.gov/whatsnew/">What's New</a></li>
<li><a href="https://medlineplus.gov/sitemap.html">Site Map</a></li>
<li><a href="https://support.nlm.nih.gov/knowledgebase/category/?id=CAT-01231&category=medlineplus&from=https%3A//medlineplus.gov/lab-tests/osmolality-tests/" target="_blank"><span>Customer Support</span></a></li>
</ul>
<ul class="follow-footer">
<li>
<a href="https://medlineplus.gov/rss.html" class="follow-item">Subscribe to RSS<img src="https://medlineplus.gov/images/feed.png" class="social-media-toolkit-icon" alt="RSS" title="RSS"></a>
</li>
<li>
<span class="follow-label">Follow us</span>
<a href="https://twitter.com/medlineplus" class="follow-item" target="_blank">
<img src="https://medlineplus.gov/images/i_share_twitter.png" class="follow-icon" alt="X" title="X">
</a>
<a href="https://facebook.com/Mplus.gov/" class="follow-item" target="_blank">
<img src="https://medlineplus.gov/images/i_share_fb.png" class="follow-icon" alt="Facebook" title="Facebook">
</a>
<a href="https://www.instagram.com/mplusgov/" class="follow-item" target="_blank">
<img src="https://medlineplus.gov/images/Instagram_Glyph_Gradient_RGB.png" class="follow-icon" alt="Instagram" title="Instagram">
</a>
</li>
<li>
<a href="https://medlineplus.gov/social-media-toolkit/" class="social-media-toolkit-item">Social Media Toolkit<img src="https://medlineplus.gov/images/i_social_media_toolkit.png" class="social-media-toolkit-icon" alt="Social Media Toolkit" title="Social Media Toolkit"></a>
</li>
</ul>
</div>
<div class="footer2">
<ul>
<li><a href=" https://www.nlm.nih.gov/web_policies.html" target='_blank'>NLM Web Policies</a></li>
<li><a href="https://medlineplus.gov/about/using/usingcontent/" >Copyright</a></li>
<li><a href="https://medlineplus.gov/accessibility.html">Accessibility</a></li>
<li><a href="https://medlineplus.gov/about/using/criteria/">Guidelines for Links</a></li>
<li><a href="https://medlineplus.gov/plugins.html">Viewers & Players</a></li>
<li><a href="https://www.hhs.gov/vulnerability-disclosure-policy/index.html" target="_blank">HHS Vulnerability Disclosure</a></li>
<li><a href="https://medlineplus.gov/medlineplus-connect/">MedlinePlus Connect for EHRs</a></li>
<li><a href="https://medlineplus.gov/about/developers/">For Developers</a></li>
</ul>
<div class="address">
<a href="https://www.nlm.nih.gov" target="_blank">National Library of Medicine</a>
<span>8600 Rockville Pike, Bethesda, MD 20894</span>
<a href="https://www.hhs.gov" target="_blank">U.S. Department of Health and Human Services</a>
<a href="https://www.nih.gov" target="_blank">National Institutes of Health</a>
</div>
<div class="date">
<span id="lastupdate">Last updated July 31, 2024</span>
</div>
<div class="return-top"><a href="#top" title="Return to top"><img class="return-top-icon" alt="Return to top" src="https://medlineplus.gov/images/return-top.png"></a></div>
</div>
</div>
</footer>
</div>
<script src="https://medlineplus.gov/jslib/jquery-3.6.0.min.js" type="text/javascript"></script>
<script src="https://medlineplus.gov/jslib/mplus-frontend-controls-new.js" type="text/javascript"></script>
<script src="https://medlineplus.gov/jslib/mplus-share.js?id=1112022" type="text/javascript"></script>
<!--[if lte IE 9]><script src="//www.nlm.nih.gov/medlineplus/jslib/jquery.placeholder.js" type="text/javascript"></script><![endif]-->
<script src="https://medlineplus.gov/jslib/control.js" type="text/javascript"></script>
<script src="https://medlineplus.gov/uswds/js/uswds.min.js" type="text/javascript"></script>
<script type='application/ld+json'>{
"@context": "http://schema.org",
"@type": "MedicalWebPage",
"headline": "Osmolality Tests",
"description": "Osmolality tests measure the amount of certain substances in your blood, urine, or stool (poop). The tests can show how your kidneys are working and whether you have an unhealthy fluid balance. The substances that the tests measure include: Glucose (sugar).; Urea (a waste product made in the liver).; Several electrolytes, such as sodium, potassium, and chloride. Electrolytes are minerals that have an electrical charge when they are dissolved in water or body fluids. They help control the balance of fluids in the body. They also help balance the acids and bases (pH balance) in your body.; Osmolality is the concentration of particles dissolved in your body fluid. The concentration is based on the amount of particles that are in a specific amount of that fluid. Different factors can make it go up or down: Your blood osmolality increases when the amount of water in your blood decreases or the number of substances such as sodium, chloride, and glucose increases. When your blood osmolality goes up it causes your kidney to hold onto water. This makes your urine more concentrated.; Your blood osmolality decreases when the amount of water in your blood increases. This makes your urine more diluted.; This process helps your body maintain a healthy fluid balance. But sometimes this balance can be thrown off. Many different conditions and factors can cause an unhealthy fluid balance, such as. too much salt intake, kidney disease, heart disease, and some types of poisoning. Other names: serum osmolality, plasma osmolality, urine osmolality, stool osmolality, osmotic gap",
"url": "https://medlineplus.gov/lab-tests/osmolality-tests/",
"publisher": {
"@type": "Organization",
"legalName": "National Library of Medicine",
"url": "https://www.nlm.nih.gov",
"brand": {
"@type": "Brand",
"name": "MedlinePlus",
"description": "MedlinePlus is an online health information resource for patients and their families and friends. It is a service of the National Library of Medicine (NLM), the world's largest medical library, and a part of the National Institutes of Health (NIH).",
"url": "https://medlineplus.gov",
"logo": {
"@type": "ImageObject",
"url": "https://medlineplus.gov/images/m_logo_primary.png"
}
},
"parentOrganization": {
"@type": "Organization",
"legalName": "National Institutes of Health",
"url": "https://www.nih.gov"
}
}
}</script>
</body>
</html>