Health Encyclopedia

Sodium - blood

Definition

This test measures the amount of sodium in the blood.

Alternative Names

Serum sodium

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test

Your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test. Do not stop or change your medications without your doctor's knowledge.

Drugs that can increase blood sodium levels include:

Anabolic steroids
Birth control pills
Certain antibiotics
Clonidine
Corticosteroids
Cough medications
Laxatives
Methyldopa
Nonsteroidal anti-inflammatory drugs (NSAIDs)

Drugs that can reduce blood sodium levels include:

Carbamazepine
Diuretics
Sulfonylureas
Triamterene
Vasopressin

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

Your doctor may order this test if you have signs of a sodium imbalance or disorders associated with abnormal sodium levels.

Your blood sodium level represents a balance between the sodium in the food and drinks you consume and the amount in urine. A small percentage is lost through stool and sweat.

Many factors affect sodium levels, including:

Recent trauma, surgery, or shock
Consuming large or small amounts of salt or fluid
Receiving intravenous (IV) fluids containing sodium
Taking diuretics or certain other medications, including the hormone aldosterone

Normal Values

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. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Abnormal sodium levels can be due to many different conditions. To help determine the cause, your health care provider will consider the total amount of fluid in your body. This is done by looking at the turgor of your skin and swelling in the ankles, feet, and legs.

For greater-than-normal sodium levels:

If the amount of fluid in your body is low, you may have fluid loss due to excessive sweating, diarrhea, use of diuretics, or burns.
If your total body water is normal, high sodium levels may be due diabetes insipidus or too little of the hormone vasopressin.
If your total body water is high, this may indicate hyperaldosteronism , Cushing syndrome, or a diet that's too high in salt or sodium bicarbonate.

For lower-than-normal sodium levels:

Low total body water and sodium levels may be due to dehydration, vomiting, diarrhea, over diuresis, or ketonuria.
Near-normal total body water may indicate SIADH, too much of the hormone vasopressin, hypothyroidism, or Addison's disease .
An increase in total body water may indicate congestive heart failure, nephrotic syndrome or other kidney disease, or cirrhosis of the liver.

Additional conditions for which the test may be performed include:

What the risks are

Possible risks from any blood test include:

Excessive bleeding
Fainting or feeling lightheaded
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Multiple punctures to locate veins

Review Date:10/26/2007
Reviewed By:Updated by: A.D.A.M. Editorial Team: Greg Juhn, M.T.P.W., David R. Eltz, Kelli A. Stacy. Previously reviewed by Robert Hurd, M.D., Department of Biology, College of Arts and Sciences, Xavier University, Cincinnati, OH. Review provided by VeriMed Healthcare Network

ADAM Quality A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial process. A.D.A.M. is also a founding member of Hi-Ethics (www.hiethics.com) and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.