Potassium Blood Test (Serum)

This test measures the potassium concentration in serum, by ion-selective electrode at Quest. Quest's code 733 is serum only (plasma is rejected); serum is separated from the cells as soon as possible after the blood clots so that potassium leaking out of cells does not raise the result.

People re-checking a potassium that was high or low on a previous panel; people with kidney disease, high blood pressure, heart disease, diabetes or adrenal disorders; people taking medicines that can affect potassium, such as diuretics, whose clinician wants it checked; and people with symptoms that can come from abnormal potassium, such as muscle weakness or cramps, fatigue or an irregular heartbeat.

Any time of day; no fasting is needed. If you are monitoring potassium on a medicine, your clinician may suggest a schedule. If a result comes back unexpectedly high with no symptoms, a repeat draw is common to rule out a falsely high (hemolyzed) sample.

Quest's reference range for adults (20 and over) for this code is 3.5-5.3 mmol/L. A high potassium (hyperkalemia) can come from kidney disease, Addison disease, poorly controlled type 1 diabetes, injury, burns or surgery, some medicines, or too much potassium from supplements; but a high result is also often an artifact of the draw, from hemolysis, fist clenching or a delayed or difficult sample, so an unexpected high value is usually repeated before any decision. A low potassium (hypokalemia) can come from diuretics, vomiting, diarrhea or heavy sweating, laxative overuse, adrenal disorders such as aldosteronism or Cushing syndrome, kidney disease or alcohol use disorder. Markedly high or low potassium can affect heart rhythm and needs prompt medical attention. JustLabs results are informational; review them with a clinician.