Blood test

Normal potassium level in the blood

Blood test
Normal potassium level in the blood
Last update: 18/03/2020

What is the normal level of potassium in the blood?

Adults: 3.5-5.1 mEq/L
Children: 3.5-5.1 mEq/L

In the International System of Units (SI), potassium in the blood is measured in mmol/L. The valence of potassium is +1 so the numeric values are the same in mmol/L or in mEq/L.

Why normal levels can differ across different labs?

Each laboratory must establish its own normal ranges for potassium in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.

Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.

What is the role of potassium?

Potassium is an electrolyte found mainly in the fluid inside of cells. Only a small percentage of the body's total potassium is available in the blood stream (2%).

Potassium is very important to maintain the electrical activity of the cells. That is essential for:

  • Conduction of nerve and muscle impulses
  • Movement of nutrients into cells
  • Movement of waste products out of cells

Potassium enters the body through diet and it is excreted primarily through urine (80%). The remaining is excreted through stool (15%) or sweat (5%).

Potassium excretion depends on the effect of aldosterone, a steroid hormone produced by the adrenal gland. If potassium level is high, the production of aldosterone in stimulated to increase the urinary potassium excretion.

What is a potassium blood test used for?

A potassium blood test is ordered for a variety of reasons:

  • To diagnoses and monitor kidney performance: If the kidneys are not working properly the level of potassium in the blood could be high because they cannot regulate the urinary potassium excretion.
  • Heart health: Potassium is essential to the proper performance of neural and muscle tissues including cardiac muscle. Potassium regulates heartbeat. Low potassium values in the blood values can lead to cardiac arrhythmias.

Causes of abnormally high levels of potassium (hyperkalemia) in the lood are:

  • Increased absorption: Dietary intake, administration of potassium-rich antibiotics, etc.
  • Decreased excretion: Hypoaldosteronism, renal insufficiency or failure, etc.

Abnormally low levels (hypokalemia) can be due to:

  • Decrease absorption: Dietary deficiency
  • Increased excretion: Hyperaldosteronism, renal tubular acidosis, diarrhea, etc.

Where can I find more information about potassium in the blood?

You can visit our pages about:

Which values are considered a normal potassium level in the blood?

The following values are considered to be normal values:

IMPORTANT: These levels are expressed in mEq/L (mmol/L). They are an example for a healthy man of about 45 years of age with no known disease, not taking any medication and with an appropriate intake of potassium in diet. The ranges can be different depending on the laboratory or on your personal circumstances.

3.5 mEq/L3.6 mEq/L3.7 mEq/L3.8 mEq/L3.9 mEq/L4 mEq/L4.1 mEq/L4.2 mEq/L
4.3 mEq/L4.4 mEq/L4.5 mEq/L4.6 mEq/L4.7 mEq/L4.8 mEq/L4.9 mEq/L5 mEq/L
5.1 mEq/L       
Medically reviewed by Javier Muga Bustamante Ph.D. on 18/03/2020


  • Concise Book of Medical Laboratory Technology: Methods and Interpretations. 2nd Edition. 2015. Ramnik Sood. ISBN: 978-93-5152-333-8. Pag. 560.
  • Tietz. Fundamentals of Clinical Chemistry. Carl A. Burtis, Edward R. Ashwood, David E. Bruns, Barbara G. Sawyer. WB Saunders Company, 2008. Pag 660. ISBN: 978-0-7216-3865-2.
  • Common Terminology Criteria for Adverse Events (CTCAE). Version 5.0.Published: November 27, 2017. U.S. Department of health and human Services. Available on:
  • Tietz NW, ed. Clinical guide to laboratory tests, 3rd ed. Philadelphia: WB Saunders Company,1995:124pp, 502-504,562-564.
  • Matsubara A, Ichihara K, Fukutani S. Determination of reference intervals for 26 commonly measured biochemical analytes with consideration of long-term within-individual variation. Clin Chem Lab Med 2008;46:691-98.

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