Potassium

This test measures the amount of potassium that is in the blood or serum. Potassium is one of the main minerals called electrolytes that are found in the blood and in all of the cells of the body.

Who is a candidate for the test?

If a doctor suspects one of the conditions that results from too high or too low a level of potassium, he or she may order this test.

How is the test performed?

In order to measure the amount of potassium in the blood, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a rubber tube called a tourniquet is tied around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial for testing in the laboratory. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.

Potassium is one of the electrolyte minerals. It is important in maintaining the body's acid-base and fluid balance. Potassium works very closely with sodium and chloride, which are also electrolyte minerals. These three minerals are in all fluids of the body. Potassium is found in fluids within cells. The other two are found in fluids outside of cells.

Information

A deficiency of potassium in the diet is unlikely and generally rare. Potassium deficiency can occur because of vomiting, diarrhea and long-term laxative and diuretic use. Low potassium levels can also be caused by chronic disease and the aging process. Kidney problems can cause a severe loss of potassium. Common problems associated with low potassium levels include:

People taking medication for high blood pressure, such as diuretics, may need to take a potassium supplement. These individuals should consult their healthcare provider.

The body protects itself from potassium toxicity by dissolving and excreting the mineral. In severe cases, a person will vomit, to keep blood levels within safe limits. When blood levels of potassium start to measurably rise it is called hyperkalemia. This is usually due to a specific cause such as reduced kidney function, increased protein breakdown or severe infection. If excess potassium cannot be excreted, it can cause heart problems. People with kidney problems may not be able to excrete excess amounts. They may be put on a potassium-restricted diet. They need to be careful of salt-substitutes. Salt-substitutes are usually made of potassium chloride. Regular salt is made from sodium chloride.

There is no Recommended Daily Allowance (RDA) for potassium. The minimum amount suggested for adults is 2,000 milligrams (mg) per day. Some experts suggest a level of about 3,500 mg per day to help protect against high blood pressure. The typical American adult gets between 800 mg and 1,500 mg per day. Following the Food Guide Pyramid should ensure a safe amount of daily potassium.

What food source is the nutrient found in?

Potassium is abundant in the diet. It is found in most

Bananas, potatoes, avocados, cantaloupe and orange juice are especially good sources of potassium. Other good sources include apricots, orange juice, and cooked or dried beans and peas.

How does the nutrient affect the body?

Potassium is found inside the cells, where it works with sodium, on the outside of the cells, to keep fluids balanced correctly. Working with sodium, potassium assists in the smooth working of muscles, such as the heart. This role is critical to basic heart function and blood pressure. It also helps transmit nerve impulses or signals.

What is involved in preparation for the test?

Normally, no preparation is required for this test.

What do the test results mean?

The normal value for potassium in the blood is 3.5 to 5.1 mEq/liter. The potassium has to remain in this range for the heart to function properly.

Potassium can become too high because of conditions including:

Many things can cause the potassium to become too low including:

Author:Clare Armstrong, MS, RD
Date Written:
Editor:Keefe, Sandy, RN, MSN
Edit Date:05/13/00
Reviewer:Kimberly A. Tessmer, RD, LD
Date Reviewed:04/05/01

Sources

Author:Melinda Ratini, DO, MS
Date Written:
Editor:Crist, Gayle P., MS, BA
Edit Date:06/21/02
Reviewer:Kathleen A. MacNaughton, RN, BSN
Date Reviewed:06/13/02