Potassium: What It Is and What Your Results Mean
Bottom line: Potassium drives your heart rhythm and muscle function. Normal is 3.5-5.0 mEq/L. Both low and high levels can cause dangerous arrhythmias.
What Is Potassium?
Potassium is the main electrolyte inside your cells and one of the most tightly controlled values in your blood, because your heart rhythm depends on it. Every heartbeat relies on potassium moving across heart muscle cell membranes, which is why both low and high levels can trigger dangerous arrhythmias.
Your kidneys regulate potassium minute to minute. Low potassium (hypokalemia) most often comes from diuretics, vomiting, or diarrhea, and frequently travels together with low magnesium. High potassium (hyperkalemia) is usually linked to kidney disease or medications that reduce potassium excretion, such as ACE inhibitors and ARBs.
One important quirk: a high potassium result is sometimes a false alarm. If red blood cells break apart in the sample tube (hemolysis), they release potassium and inflate the number. Doctors commonly repeat an unexpected high result before acting on it.
Potassium Reference Ranges
| Classification | Range (mEq/L) |
|---|---|
| Severely Low (Severe Hypokalemia) | Below 3.4 |
| Low (Hypokalemia) | 2.5 - 3.4 |
| Normal | 3.5 - 5.0 |
| High (Hyperkalemia) | 5.1 - 5.9 |
| Severely High (Life-Threatening) | 6.0 - 9.0 |
What Affects Your Potassium Levels?
- Kidney function (the main regulator of potassium)
- Diuretics, ACE inhibitors, ARBs, and potassium-sparing medications
- Vomiting, diarrhea, and laxative use
- Magnesium level (low magnesium causes stubborn low potassium)
- Potassium supplements and salt substitutes
- Sample handling (hemolyzed blood draws falsely raise results)
When to Get Tested
Potassium is part of every basic and comprehensive metabolic panel. Anyone taking diuretics, ACE inhibitors, ARBs, or with kidney disease should have potassium checked regularly, often every 3 to 6 months, because these are the most common causes of dangerous shifts.
Look Up Your Potassium Result
Select your value below to see a detailed breakdown of what it means:
Read the Full Blood Test Guide
Frequently Asked Questions
3.5 to 5.0 mEq/L is the standard normal range. Below 3.5 is hypokalemia and above 5.0 is hyperkalemia. Values below 2.5 or above 6.0 mEq/L are medical emergencies because of arrhythmia risk.
Yes, and it is common. If red blood cells rupture in the sample (hemolysis), potassium leaks out and falsely elevates the result. Tight tourniquets and fist clenching during the draw can do the same. Doctors usually repeat an unexpected high value before treating it.
Bananas are famous, but potatoes, beans, lentils, spinach, avocados, oranges, and tomatoes contain as much or more. People with kidney disease may need to limit these; people on certain diuretics may need more. Follow your doctor's guidance for your situation.