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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 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
9482-1
Short code
Potassium Wat-mCnc
Synonyms
Potassium Wat-mCnc
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?

Doctors may order potassium tests to check for imbalances caused by conditions like kidney problems, heart disease, or certain medications. It can also help monitor treatment for conditions like high blood pressure or heart rhythm disorders.

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. Bring any medications you’re currently taking to your appointment.

How the Test Works

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where potassium levels are measured using an automated analyzer.

What the Results Mean

Results are compared to standard reference ranges, but exact values can vary by lab. Low potassium (hypokalemia) may cause muscle weakness or irregular heartbeat, while high potassium (hyperkalemia) can affect heart rhythm.

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.

Clinical Significance

Short name

Serum Potassium

Frequently asked questions

Low potassium levels may indicate conditions like diarrhea, vomiting, or kidney issues, while high levels could result from kidney failure, excessive potassium supplements, or certain medications like potassium-sparing diuretics.
Potassium tests are critical for diagnosing and managing heart-related problems, electrolyte imbalances, and other health conditions. Abnormal results may prompt further testing or adjustments to treatment.
What causes potassium levels to be too low?
Low potassium can stem from vomiting, diarrhea, excessive sweating, certain medications (like diuretics), or kidney problems that don’t properly filter potassium from the blood.
What causes potassium levels to be too high?
High potassium is often linked to kidney failure, excessive intake of potassium supplements, or conditions like severe dehydration or metabolic acidosis. Rarely, it can result from genetic disorders or certain tumors.
  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