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What is the Potassium test?

Potassium test, also called serum potassium test or K+ test measures the level of potassium in serum, which is the fluid part of blood. This test is a part of the regular basic or comprehensive metabolic panel test. Maximum potassium content in the body, which is about 90%, is found inside cells, but some amount is also found in the blood. Potassium is obtained from various dietary sources such as milk, fish, vegetables, pulses, fruits, nuts and seeds

This mineral plays many vital functions in the body, such as helping:

  • Nutrients move inside cells
  • Remove waste materials out of cells
  • Communication between nerves and muscles
  • Maintain the fluid balance in the body
  • Healthy functioning of the heart

The hormone aldosterone controls potassium levels in the body.  Potassium test is used to identify medical conditions since any changes in normal levels of potassium are indicative of abnormalities.

  1. Why is Potassium test performed?
  2. How do you prepare for Potassium test?
  3. How is Potassium test performed?
  4. What do Potassium test results mean?

This test is primarily performed to diagnose and monitor kidney disease as it is the most common cause of abnormally high levels of potassium. Potassium test is recommended in individuals with symptoms of hypokalemia or hyperkalemia. Common symptoms associated with hypokalemia are:

Symptoms related to hyperkalemia are:

It is also recommended in individuals with metabolic acidosis due to uncontrolled diabetes or excessive vomiting.

No special preparations are required for this test. However, you should inform the doctor about any medications taken before the test, including herbs, vitamins or minerals, as these may affect test results. Some medicines that affect the levels of potassium and give false results include non-steroidal anti-inflammatory drugs, penicillin, glucose and diuretics.

Some medications that increase potassium levels in the blood are histamines, heparin, epinephrine, isoniazid and aminocaproic acid. Some drugs that decrease the levels of potassium in the blood are aminosalicylic acid, insulin, penicillin G, carbenicillin and amphotericin B.

The doctor may recommend stopping medications before the test. However, do not stop or alter the dose of any medicines on your own.     

For this test, a blood sample is drawn by inserting a needle into a vein in the arm. It may cause moderate pain, and pricking and a stinging sensation. Throbbing may be experienced for some time after the test.

Some of the risks associated with the collection of a blood sample include excessive bleeding, a feeling of lightheadedness, blood accumulation under the skin and infection at the site of needle prick.

Normal results:

The normal levels of potassium are 3.7 to 5.2 mmol/L.

Abnormal results:

Higher or lower than the normal level of potassium indicates certain conditions. Hyperkalemia can be due to:

  • Excess dietary intake of potassium
  • Certain medicines
  • Destruction of red blood cells
  • Blood transfusion
  • Respiratory or metabolic acidosis
  • Kidney failure
  • Hyperkalemic periodic paralysis, a genetic disease that causes episodes of severe muscle weakness and increased potassium levels
  • Crushed tissue injury

In some instances, when there is difficulty in locating a vein for collection of a blood sample, tissue injury occurs, leading to the destruction of red blood cells, which in turn causes the release of potassium. This can give a falsely high potassium level.

Rarely, hyperaldosteronism (excessive levels of hormone aldosterone) may also cause hyperkalemia.

Hypokalemia can be due to:

  • Vomiting or chronic diarrhoea
  • Medicines like furosemide, hydrochlorothiazide and indapamide
  • Insufficient dietary consumption of potassium
  • Renal artery stenosis, i.e., narrowing of the arteries that supply blood to the kidneys
  • Hypokalemic periodic paralysis, which is a condition that causes episodes of extreme weakness of muscles and reduced levels of potassium

Rarely, Cushing syndrome and renal tubular acidosis may also cause hypokalemia.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.  

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References

  1. National Health Service [Internet]. UK; Potassium test.
  2. David B. Mount. Disorders of Potassium Balance . Elsevier, February 23, 2017 [Internet]
  3. University of Rochester Medical Center Rochester, NY. [Internet] Potassium
  4. Karl Skorecki, Glenn Chertow, Philip Marsden, Maarten Taal, Alan Yu. Brenner and Rector's The Kidney. Elsevier; Published Date: 28th October 2015
  5. Lee Goldman, Andrew I. Schafer. Cecil Medicine. Elsevier; Saunders; Published Date: 22nd July 2011
  6. National Center for Advancing and Translational Sciences. Hyperkalemic periodic paralysis. Genetic and Rare Diseases Information Center
  7. National Institutes of Health; [Internet]. U.S. National Library of Medicine. Hypokalemic periodic paralysis