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Potassium (K) in Blood

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A potassium test checks how much potassium is in the blood. Potassium is an electrolyte and mineral.

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Blood potassium levels also vary with age.

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Potassium (K)1
Adults:

3.5–5.2 milliequivalents per liter (mEq/L) or 3.5–5.2 millimoles per liter (mmol/L)

Children:

3.4–4.7 mEq/L or 3.4–4.7 mmol/L

Infants:

4.1–5.3 mEq/L or 4.1–5.3 mmol/L

Newborns:

3.7–5.9 mEq/L or 3.7–5.9 mmol/L

Many conditions can affect potassium levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.

High values

  • High blood potassium levels may be caused by damage or injury to the kidneys. This prevents the kidneys from removing potassium from the blood normally.
  • High blood potassium levels can also be caused by conditions that move potassium from the body's cells into the blood. These conditions include severe burns, crushing injuries, heart attack, and diabetic ketoacidosis.
  • Taking too many potassium supplements can also cause high levels of potassium in the blood.
  • Too much acid (pH) in the blood makes potassium levels higher by causing the potassium in the body's cells to "leak" out of cells and into the blood.
  • Some medicines, such as aldosterone antagonists and angiotensin-converting enzyme (ACE) inhibitors, can cause high potassium levels.

Low values

  • Low blood potassium levels can be caused by high levels of aldosterone (hyperaldosteronism) made by the adrenal glands.
  • Other conditions that can cause low blood potassium levels include severe burns, cystic fibrosis, alcoholism, Cushing's syndrome, dehydration, malnutrition, vomiting, diarrhea and certain kidney diseases, such as Bartter's syndrome. Bartter's syndrome is a condition characterized by enlargement of certain kidney cells. It is more common in children and may be linked to an abnormally short stature (dwarfism). The cause of Bartter's syndrome is not fully known.
  • Medicines, such as diuretics, are a common cause of low potassium levels.

WebMD Medical Reference from Healthwise

Last Updated: September 04, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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