$7.00
Priced per marker, with baseline labs included. You’ll see your total before you pay.
Metabolism & organs
Serum osmolality test
Measures blood concentration; evaluates hydration, sodium disorders, and pituitary function.
At a glance
In about 5 days
Most results are ready in about 5 days. Some specialty markers can take up to 21 days.
Check before your draw
This marker has no preparation tag, but it can still need preparation. Contact us before your draw if you’re not sure.
Walk in at Quest
Your lab order arrives by email. Most Quest locations take walk-ins, so bring it with a photo ID.
What it measures
Osmolality measures how concentrated your blood is, meaning how much salt, sugar and other dissolved particles it holds. It helps show whether your body’s water balance is on track.
Why it matters for women
Morning sickness that won’t let up can leave you dehydrated, which can raise this result. Some common medicines, including water pills and certain antidepressants, can lower sodium and pull it down. It’s usually read with your sodium and blood sugar results to find the cause of an imbalance.
You might check it if…
- you’re very thirsty or urinating much more than usual
- a past test showed high or low sodium
- you’ve had a lot of vomiting, including during pregnancy
What your result may mean
High Serum osmolality: what it may mean
High serum osmolality may mean your blood is too concentrated. It can happen with dehydration, uncontrolled diabetes or swallowing a toxin such as methanol, ethylene glycol or ethanol (alcohol). Morning sickness that won't let up (hyperemesis gravidarum) can leave you dehydrated and push this result up, and a rare form of diabetes insipidus can appear in pregnancy. You may notice thirst, a dry mouth, less urine or confusion. Your sodium, blood sugar and kidney results can help narrow down the reason.
Low Serum osmolality: what it may mean
Low serum osmolality may mean there is too much water for the salt and other particles in your blood. It can happen with water overload, drinking very large amounts of fluid (polydipsia), eating very little (low solute intake) or SIADH, when your body holds on to too much water. Water pills and certain antidepressants can lower sodium and pull this result down. It can also run slightly lower in pregnancy. Headache, nausea or confusion can appear if it drops quickly, and a clinician may check your sodium and urine results to find the reason.
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These notes provide context and do not diagnose a condition. Not yet available in NY, NJ, RI, HI, ND, SD or WV.