sodium test checks how much sodium is in the blood. Sodium is
both an electrolyte and mineral. It helps keep the water (the amount of fluid
inside and outside the body's cells) and electrolyte balance of the body.
Sodium is also important in how nerves and muscles work.
the sodium in the body (about 85%) is found in blood and
lymph fluid. Sodium levels in the body are partly
controlled by a
hormone called aldosterone, which is made by the
adrenal glands. Aldosterone levels tell the kidneys
when to hold sodium in the body instead of passing it in the urine. Small amounts of sodium are also lost
through the skin when you sweat.
Most foods have sodium naturally
in them or as an ingredient in cooking. Sodium is found in table salt as sodium
chloride or in baking soda as sodium bicarbonate. Many medicines and other
products also have sodium in them, including laxatives, aspirin, mouthwash, and
Low sodium levels
are uncommon and are most often caused by heart failure, malnutrition, and diarrhea.
such as potassium, calcium, chloride, magnesium, and phosphate, may be checked
in a blood sample at the same time as a blood test for sodium.
A blood test to check sodium levels is
You do not need to do anything before
having this test.
Talk to your doctor about any
concerns you have regarding the need for the test, its risks, how it will be
done, or what the results will mean. To help you understand the importance of
this test, fill out the
medical test information form(What is a PDF document?).
The health professional drawing blood
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
There is very little chance of a problem from
having a blood sample taken from a vein.
A sodium test checks how much sodium (an
electrolyte and a mineral) is in the blood.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Results are ready in 1 day.
milliequivalents per liter (mEq/L) or 136–145
millimoles per liter (mmol/L)
Many conditions can affect sodium levels. Your doctor will
talk with you about any abnormal results that may be related to your symptoms
and past health.
Reasons you may not be able to
have the test or why the results may not be helpful include:
CitationsPagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.Other Works ConsultedChernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
September 4, 2012
Adam Husney, MD - Family Medicine & Avery L. Seifert, MD - Urology
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