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Home > Patient & Family Resources > Health Library > Potassium (K) in Blood Test
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A potassium test checks how much potassium is in the blood. Potassium is both an electrolyte and a mineral. It helps keep the water (the amount of fluid inside and outside the body's cells) and electrolyte balance of the body. Potassium is also important in how nerves and muscles work.
Potassium levels often change with sodium levels. When sodium levels go up, potassium levels go down, and when sodium levels go down, potassium levels go up. Potassium levels are also affected by a hormone called aldosterone, which is made by the adrenal glands.
Potassium levels can be affected by how the kidneys are working, the blood pH, the amount of potassium you eat, the hormone levels in your body, severe vomiting, and taking certain medicines, such as diuretics and potassium supplements. Certain cancer treatments that destroy cancer cells can also make potassium levels high.
Many foods are rich in potassium, including bananas, orange juice, spinach, and potatoes. A balanced diet has enough potassium for the body's needs. But if your potassium levels get low, it can take some time for your body to start holding on to potassium. In the meantime, potassium is still passed in the urine, so you may end up with very low levels of potassium in your body, which can be dangerous.
A potassium level that is too high or too low can be serious. Abnormal potassium levels may cause symptoms such as muscle cramps or weakness, nausea, diarrhea, frequent urination, dehydration, low blood pressure, confusion, irritability, paralysis, and changes in heart rhythm.
Other electrolytes, such as sodium, calcium, chloride, magnesium, and phosphate, may be checked in a blood sample at the same time as a blood test for potassium.
A blood test to check potassium is done to:
In general, there's nothing you have to do before this test, unless your doctor tells you to.
A health professional uses a needle to take a blood sample, usually from the arm.
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
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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3.5–5.2 milliequivalents per liter (mEq/L) or 3.5–5.2 millimoles per liter (mmol/L)
3.4–4.7 mEq/L or 3.4–4.7 mmol/L
4.1–5.3 mEq/L or 4.1–5.3 mmol/L
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.
Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Current as of:
June 17, 2021
Author: Healthwise StaffMedical Review: Adam Husney MD - Family MedicineE. Gregory Thompson MD - Internal MedicineMartin J. Gabica MD - Family Medicine
Current as of: June 17, 2021
Author: Healthwise Staff
Medical Review:Adam Husney MD - Family Medicine & E. Gregory Thompson MD - Internal Medicine & Martin J. Gabica MD - Family Medicine
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