Serum sodium; Sodium - serum
The sodium blood test measures the concentration of sodium in the blood.
Sodium can also be measured using a urine test.
A blood sample is needed.
Your health care provider may tell you to temporarily stop taking medicines that may affect the test. These include:
Do not stop taking any medicine before talking to your provider.
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
Sodium is a substance that the body needs to work properly. Sodium is found in most foods. The most common form of sodium is sodium chloride, which is table salt.
This test is usually done as part of an electrolyte or basic metabolic panel blood test.
Your blood sodium level represents a balance between the sodium and water in the food and drinks you consume and the amount in your urine. A small amount is lost through stool and sweat.
Many things can affect this balance. Your provider may order this test if you:
The normal range for blood sodium levels is 135 to 145 milliequivalents per liter (mEq/L).
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.
An abnormal sodium level can be due to many different conditions.
Higher than normal sodium level is called hypernatremia. It may be due to:
Lower than normal sodium level is called hyponatremia. It may be due to:
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
Al-Awqati Q. Disorders of sodium and water. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 108.
Oh MS, Briefel G, Pincus MR. Evaluation of renal function, water, electrolytes, and acid-base balance. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 15BACK TO TOP
Review Date: 11/6/2021
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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