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The Serum Osmolality Test checks how concentrated your blood is. You may also hear it called serum osmolality, plasma osmolality, or blood osmolality. Once your ready, you can book at participating labs on LabFinder.
This test, sometimes listed as plasma osmolality or Osm serum, measures particles like salts, sugar, and urea in your blood. It helps show if your body has the right water balance and can point toward dehydration, over hydration, or a problem with kidney or hormone control.
Common reasons: checking confusing low sodium levels, signs of dehydration or too much water, symptoms that suggest diabetes insipidus, possible SIADH, kidney issues, or to review unusual lab results. Doctors may also order it when certain medicines or substances could affect water balance.
You will check in and confirm your name and order. A phlebotomist cleans your arm, places a small needle, and draws a small tube of blood. A bandage goes on, and you are free to leave. The visit usually takes 10 to 20 minutes, with the blood draw itself lasting only a minute or two.
Yes, this is a quick, routine blood draw and is considered very safe. You might feel a quick pinch, notice a small bruise, or feel a little lightheaded for a moment afterward, but those effects usually fade quickly. Be sure to tell the staff if you take blood thinners, have a bleeding disorder, or if you have fainted during blood draws before. They will take extra care to keep you comfortable. Let the team know if you recently received IV fluids or mannitol, since that can change results.
Ask about fluids: drink as usual unless your doctor gave special steps. Avoid hard workouts: extreme exercise right before testing can shift water balance. Fasting only if told: some doctors pair this test with other labs that may need fasting. Bring a photo ID and any recent results your doctor wants the lab to review.
Dehydration, over hydration with low sodium, diabetes insipidus, SIADH, kidney disease, very high blood sugar, and certain toxin exposures such as antifreeze. Results are read in context. Your doctor will review your results with your symptoms and history before planning next steps.
On LabFinder, you can compare locations, see time slots, and book online at participating labs. It is easy to search for a convenient location in your area or by city or ZIP. Coverage varies by plan and provider, so check your benefits when you schedule.
Book on LabFinder: find a lab today on our lab finder and request a test doctor guided.
The information on this page and throughout the LabFinder website and mobile app is for general informational purposes only. It is not intended to serve as medical advice, diagnosis, or treatment. For personalized medical advice or specific health concerns, please consult your healthcare provider directly.
Booking a Serum Osmolality Test is easy using LabFinder. Just choose your location and enter your insurance information to find the closest Serum Osmolality Test near you.
To make a same-day appointment for a Serum Osmolality Test, just choose your location and your insurance information to find the closest Serum Osmolality Test location near you. If there's availability for a same-day appointment at a nearby lab location, then you will be able to book it easily through LabFinder.
LabFinder allows you to easily schedule a Serum Osmolality Test. You can search by location and insurance to easily book a Serum Osmolality Test near you.
LabFinder allows you to easily make an appointment for a Serum Osmolality Test online. To make an appointment for a Serum Osmolality Test online, just choose your location and your insurance information to find the closest Serum Osmolality Test near you.
Yes, you can get a Serum Osmolality Test without insurance. LabFinder allows you to search and select "Self-Pay" when booking a Serum Osmolality Test. While pricing for the test may not be immediately available, please check by calling the lab company directly for pricing.
