How It Feels

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 pinch.

Risks

There is very little chance of a problem from having blood sample taken from a vein.

• You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
• In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
• Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

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.

Results are ready in 1 day.

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 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 associated with 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.