Potassium levels: what's normal, high and low
An electrolyte essential for heart, muscle, and nerve function.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
The short answer
Potassium is measured with a standard blood draw after an 8–12 hour fast. A typical reference range is 3.50 – 5.00 mmol/L. At TestWell it's $20.99 all-in as Basic Metabolic Panel, results in 1–3 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.
- Units
- mmol/L / mEq/L
- Sample
- Blood draw
- Fasting
- 8–12 hours
- Results
- 1–3 business days
- Price
- $20.99
- Labs
- Quest or Labcorp · BioReference in NY/NJ
Potassium Reference Range
These are the typical adult reference ranges used by major US labs. Your report will include the specific range used by the lab that processed your sample.
| Population | Range |
|---|---|
| age 18+ | 3.50 – 5.00 mmol/L |
Reference ranges are educational. Always interpret your result with the specific range printed on your lab report and discuss anything outside the range with a clinician.
What your Potassium result may mean
Can reflect kidney issues, certain medications, or sample handling issues. Severe elevations can affect heart rhythm.
What a high Potassium means: causes, symptoms, next steps →Can reflect diuretic use, GI losses, or low intake.
What a low Potassium means: causes, symptoms, next steps →Educational only — not a diagnosis. Many factors can influence a single result. Discuss anything that concerns you with a healthcare provider.
How do you get a Potassium test?
Order online, a licensed physician reviews the requisition, and you walk into a nearby lab for the draw. Potassium is available on its own or inside these panels — panels cost less per marker when you want the fuller picture.
| Option | Includes | Price |
|---|---|---|
| Basic Metabolic Panel | This marker only | $20.99 |
Quest vs. Labcorp for Potassium: which lab should you pick?
Both are CLIA-certified national labs and the result is clinically equivalent, so pick whichever location is closer. Your report will print that lab's own reference range, which can differ slightly from the table above.
| Lab | Available | Price |
|---|---|---|
| Quest Diagnostics | Yes | $20.99 |
| Labcorp | Yes | $21.99 |
| BioReference (NY & NJ) | Yes | $22.99 |
Need help choosing a location? Use the lab finder to see draw sites near your ZIP.
Frequently asked
Can reflect kidney issues, certain medications, or sample handling issues. Severe elevations can affect heart rhythm. A single result above the reference range is a prompt to look closer with a clinician — often a repeat test and related markers — not a diagnosis on its own.
Ready to test your potassium?
Order in two minutes, get physician-approved, and visit a lab the same day. Starts at $20.99.