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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
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
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
Many foods are rich in potassium, including scallops,
potatoes, figs, bananas, prune juice, orange juice, and squash. 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.
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
A blood test to check
potassium is done to:
You do not need to do anything before
having this test.
Talk to your doctor about any
concerns you have regarding the need for the test, its risks, how it will be
done, or what the results will mean. To help you understand the importance of
this test, fill out the
medical test information form(What is a PDF document?).
The health professional drawing blood
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
There is very little chance of a problem from
having blood sample taken from a vein.
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.
ready in 1 day.
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.
Reasons you may not be able to
have the test or why the results may not be helpful include:
To learn more, see:
CitationsPagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.Other Works ConsultedChernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
Saunders.Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
September 4, 2012
Adam Husney, MD - Family Medicine & Avery L. Seifert, MD - Urology
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