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Blood Test for potassium

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What is Blood Test for potassium?

A test for potassium or K+ measures the level of this mineral in the blood. Potassium is an essential electrolyte that is required for normal functioning of nerves and muscles as well as the heart. It maintains water balance and pH level within the body. It is also responsible for the movement of nutrients into the cells and waste products out of the cells. Most of the potassium, about 98%, exists within the cells of the body. This may be leaked into the bloodstream due to several reasons, causing a rise in levels.

Why is it conducted?

Variations in potassium levels can have serious repercussions for health. It can lead to muscle cramps, disturbances in heart rate as well as blood pressure, paralysis, nausea, diarrhea and dehydration. This urine test for potassium is most commonly ordered to gauge the functioning of the kidneys as potassium is excreted by the kidneys. It is often requested with tests for other electrolytes, especially sodium. There is an inverse relation between sodium and potassium, wherein rise in one leads to fall in the other.

Who should go for it?

  • Persons suffering from high blood pressure or electrical irregularities of the heart are often advised this test.
  • Persons who have been prescribed diuretics or undergo dialysis are advised this test.
  • Blood test for potassium is also advised when the body’s pH balance is disturbed and metabolic acidosis is suspected. This can be in the case of uncontrolled diabetes, excess vomiting or diarrhea.
  • Persons who are receiving nutrition intravenously through a drip are often ordered this test to measure the level of potassium.
  • This test is sometimes carried out when an attack of paralysis occurs.
  • Persons undergoing treatment for cancer may need to have their potassium levels checked as treatment can sometimes damage cells. This in turn leads to high levels of potassium.
  • Potassium levels also need to be checked for persons who are under treatment for high or low potassium.


This is a simple blood test that requires no special precautions. Blood will be drawn by a technician from a vein at the inside of the elbow. If there are problems when drawing blood for potassium testing it can cause potassium levels to rise due to destruction of red blood cells. This can lead to a false result of high potassium.

Interpretation of results

The normal ranges lie between 3.7 mEq/L to 5.2 mEq/L. Some medicines are known to affect potassium levels in the blood, such as, NSAIDs, insulin, glucosteroids, medicines like ACE inhibitors or ARBs for hypertension and heart attacks.

High values indicate a number of conditions such as kidney disease, heart attack, severe burns or injuries and diabetes that is not controlled properly. In some cases, it may be due to high intake of potassium either as supplements or in diet. In rare situations it may be due to deficiency of the hormone aldosterone produced by the adrenals or due to adrenal insufficiency. Other factors that may cause rise in levels is blood transfusion, destruction of red blood cells or even tumor cells. Besides, potassium levels tend to be high after surgery.

Low values may be caused by prolonged diarrhea or vomiting, use of diuretics, excess use of laxatives, heavy sweating, deficiency of potassium in diet, alcoholism and some kidney diseases. In some cases it may be due to excess of the hormone aldosterone. Persons who have eating disorders or suffer from malnutrition may also have low potassium levels.

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Written by: Nandita tripati

Date last updated: January 10, 2015

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