Potassium

Potassium is an electrolyte your blood test measures to check how well your nerves, muscles, and heart are working. In most adults a normal serum potassium level falls between 3.7 and 5.2 mEq/L.

Ranges vary between labs, so compare to the range on your own lab report.

What potassium measures

Potassium is a mineral and electrolyte that carries a small electrical charge inside your cells. It helps your nerves send signals, your muscles contract, and your heart beat with a steady rhythm. A serum potassium test shows the concentration circulating in your blood, which your kidneys and hormones normally keep in a tight range.

What high or low levels mean

A high result (hyperkalemia) often points to reduced kidney function, since your kidneys clear most potassium from your body. Certain medications, such as ACE inhibitors, ARBs, and potassium-sparing diuretics, along with tissue injury, can also raise it. High potassium may cause muscle weakness or a slow or irregular heartbeat, and very high levels can be life threatening.

A low result (hypokalemia) usually reflects potassium loss from vomiting, diarrhea, heavy sweating, or diuretic use. You may notice cramps, fatigue, weakness, or an irregular heartbeat.

Mild shifts are common and often correctable, but your clinician may repeat the test, review your medications, or check kidney function. Seek care promptly, as extreme high or low values are medical emergencies that can disturb heart rhythm.

Potassium FAQ

What is the most common cause of high potassium?

Reduced kidney function is the leading cause, because healthy kidneys remove excess potassium. Medications that limit potassium excretion and conditions involving tissue breakdown can also push your level higher than normal.

Can diet raise my potassium level?

For most people with healthy kidneys, diet alone rarely causes a high result, since the body excretes the extra. If your kidney function is reduced, potassium-rich foods and supplements can matter more.

Should I fast before a potassium test?

Usually you do not need to fast for a potassium test alone, but it is often drawn as part of a panel that requires fasting. Follow the specific instructions your clinician or lab gives you.

Read alongside your other electrolytes: sodium, chloride, and carbon dioxide (bicarbonate).

Sources

• MedlinePlus Medical Encyclopedia, Potassium test.

• NCBI Clinical Methods, Serum Potassium.