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Serum or plasma mass concentration of potassium (measured by ion-selective electrode)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of potassium, a vital mineral, in your blood. Potassium helps maintain proper heart rhythm, muscle function, and fluid balance.

Quick summary

["Potassium levels help doctors check for heart rhythm issues, kidney problems, or other health concerns."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
56639-8
Short code
MEK Ur-sCnc
Synonyms
MEK Ur-sCnc
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test if you have symptoms like muscle weakness, irregular heartbeat, or signs of low or high potassium levels. It’s also used to monitor conditions like kidney disease, heart problems, or certain medications that affect potassium.

What to Expect Before the Test

No special preparation is needed, but avoid eating or drinking anything (except water) for 8–12 hours before the test if instructed. Tell your doctor about any medications, supplements, or recent illnesses.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. You may feel a small pinch, but it usually takes only a few minutes. The blood sample is then sent to a lab for analysis.

What Are the Results?

Results are typically reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). Your doctor will compare these numbers to your specific reference range and explain what they mean for your health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low potassium (hypokalemia) can cause muscle cramps, fatigue, irregular heartbeat, or even heart failure. High potassium (hyperkalemia) may lead to weakness, numbness, or dangerous heart rhythms. Both extremes can be dangerous and require medical attention.

Short name

Potassium level (serum/plasma)

Frequently asked questions

What causes potassium levels to change?
Potassium levels can drop due to vomiting, diarrhea, excessive sweating, or certain medications (like diuretics). They may rise from kidney problems, severe dehydration, or conditions like Addison’s disease. Lifestyle factors, such as high salt intake or low potassium foods, can also influence results.
How long does it take to get results?
Results are usually available within 1–2 business days, depending on your lab. Your doctor will discuss them with you during your follow-up visit.
Can I adjust my diet before this test?
Yes, if your doctor instructed you to avoid high-potassium foods (like bananas, spinach, or potatoes) or certain medications, follow their guidance. Otherwise, eating normally is fine unless specified otherwise.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 16, 2026. · Read our editorial policy