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Potassium (Serum or Plasma Concentration)

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

This test measures the amount of potassium, a mineral essential for muscle and nerve function, in your blood serum or plasma.

Quick summary

["Potassium levels help assess heart health and electrolyte balance."]

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

Key facts at a glance

LOINC
2825-8
Short code
Potassium Sal-sCnc
Synonyms
Potassium Sal-sCnc
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
3.5
Ref high
5
Critical range
2.5 N/A – 6.5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84132
SNOMED
110742001
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for conditions affecting your heart, kidneys, or other organs. It can also help diagnose or monitor symptoms like muscle weakness, irregular heartbeat, or unexplained fatigue.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it involves a blood draw. Bring any medications or supplements you’re currently taking to your appointment.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. The blood sample is then sent to a lab for analysis. The test typically takes a few minutes, and you may feel slight discomfort but no lasting effects.

What the Results Mean

Results are compared to a standard range for healthy adults. Low potassium (hypokalemia) or high potassium (hyperkalemia) can indicate underlying health issues, such as kidney problems, heart conditions, or certain medications affecting electrolyte balance.

Reference range

Adult: 3.5-5.0 mmol/LN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Potassium

Frequently asked questions

How often should potassium tests be done?
The frequency depends on your health status. Routine tests are usually not recommended unless you have risk factors (e.g., kidney disease, heart conditions, or use of diuretics). Follow your doctor’s advice for follow-up testing.
What symptoms might trigger a potassium test?
Symptoms that may prompt a potassium test include muscle weakness or spasms, irregular heartbeat, fatigue, or unexplained nausea. Your doctor may also order it as part of a broader blood panel if you have symptoms of electrolyte imbalances.
Can diet affect potassium test results?
Yes, diet can influence potassium levels. High-potassium foods (e.g., bananas, spinach) may temporarily raise potassium in your blood, while low-potassium diets could lower it. Avoid eating high-potassium foods 24 hours before the test if instructed by your provider.
  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