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Potassium concentration in serum/plasma

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

This test measures the amount of potassium, a mineral essential for heart function and nerve signaling, in your blood.

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
32336-0
Short code
Potassium Spec-sCnc
Synonyms
Potassium Spec-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 doctor may order this test to check for conditions affecting your heart, kidneys, or digestion, or to monitor medications that can influence potassium levels. It’s also used in cases of dehydration, vomiting, or diarrhea that might lead to imbalances.

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 your blood is drawn early in the morning. Wear comfortable clothing and avoid heavy exercise the day of the test.

What Happens During the Test?

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

What Are Normal Results?

Normal results vary by lab and individual, but they typically fall within a specific range. Your doctor will compare your results to your personal baseline or medical needs.

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/plasma potassium

Frequently asked questions

What causes potassium levels to change?
Potassium levels can be affected by diet (e.g., high potassium foods like bananas or spinach), kidney function, medications (like diuretics or certain heart medications), or conditions like vomiting, diarrhea, or kidney disease.
How long does it take to get results?
Results are usually available within 24 hours, but timing can vary depending on your lab’s schedule and whether follow-up tests are needed.
Can I eat or drink before the test?
If fasting is required, follow your doctor’s instructions. Otherwise, you can eat and drink normally 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