Potassium Test
A potassium test measures the amount of potassium in your blood. This essential mineral and electrolyte helps your nerves send signals, keeps your muscles working properly, and supports a steady heartbeat while maintaining healthy fluid balance in your body.
{"Potassium is a vital electrolyte that helps regulate heart rhythm and muscle function","Normal range is typically 3.5-5.0 mmol/L","Both high and low potassium levels can cause serious health problems","The test requires a simple blood draw","Certain medications and kidney function can affect potassium levels"}
Key facts at a glance
- LOINC
- 2823-3
- Short code
- K+
- Synonyms
- —
- Category
- electrolyte
- Sample
- serum
- Container
- Serum Separator Tube (SST) or Plain Red Top Tube
- Units
- mmol/L
- Ref low
- 3.5
- Ref high
- 5
- Critical range
- 2.5 mmol/L – 6.5 mmol/L
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- ion-selective-electrode
- CPT
- 84132
- SNOMED
- 365906006
- Specimen volume
- 1-3 mL
- Stability
- Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 30 days
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 1–2 hours
What is this test?
A potassium test is a blood test that measures the concentration of potassium in your blood serum. Potassium is a type of electrolyte—a mineral in your blood and other body fluids that carries an electric charge. It plays a crucial role in maintaining the electrical activity of your heart, enabling muscle contractions, and supporting proper nerve function.
Why is it important?
Potassium helps your body's cells work properly. It works with sodium to control the body's fluid balance, supports nerve impulse transmission, and helps muscles contract—including the heart muscle. Maintaining the right balance of potassium is essential for overall health.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm. The procedure is quick and typically takes less than a minute. You may feel a slight pinch or sting when the needle is inserted. The sample is then sent to a laboratory for analysis.
How to prepare?
No special preparation is usually required for a potassium test. However, your doctor may ask you to avoid certain medications or supplements before the test, as some substances can affect potassium levels. Always follow your healthcare provider's specific instructions.
Reference range
Adult reference range: 3.5-5.0 mmol/L. Pediatric ranges vary by age: Neonates (3.7-5.9 mmol/L), Infants (4.1-5.3 mmol/L), Children (3.5-5.0 mmol/L).mmol/L
No fasting required. Avoid strenuous exercise immediately before collection as it may transiently elevate potassium levels. Inform laboratory of any potassium supplements or medications that affect potassium levels (e.g., diuretics, ACE inhibitors, NSAIDs).
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Abnormal potassium levels can indicate various health conditions. High potassium levels (hyperkalemia) may suggest kidney disease, certain medications (such as potassium-sparing diuretics), or tissue breakdown. Low potassium levels (hypokalemia) may result from vomiting, diarrhea, excessive sweating, or use of certain diuretics. Both conditions can affect heart rhythm and muscle function, potentially leading to serious complications if left untreated.
Short name
K
Part of panels
Frequently asked questions
What is the normal potassium level?
Do I need to fast before the test?
What happens if my potassium level is too high or too low?
Can medications affect my potassium level?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 10, 2026. · Read our editorial policy