Sodium blood test
The sodium blood test measures the amount of sodium in the blood.
Sodium can also be measured using a urine test.
Serum sodium; Sodium - serum
How the Test is Performed
A blood sample is needed.
How to Prepare for the Test
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.
How the Test will Feel
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.
Why the Test is Performed
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.
What Abnormal Results Mean
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:
Chernecky CC, Berger BJ. Sodium, plasma - serum or urine. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:1026-1029.
Slotki I, Skorecki K. Disorders of sodium and water homeostasis. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 116.
Review Date: 11/20/2017
Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. 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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