Skip to content

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 muscle contractions, 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
39785-1
Short code
Potassium DiafP-sCnc
Synonyms
Potassium DiafP-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 potassium levels, such as kidney problems, heart rhythm issues, or dehydration. It’s often done alongside other blood tests to monitor overall health or diagnose symptoms like muscle weakness, irregular heartbeat, or nausea.

What to Expect Before the Test

No special preparation is needed, but avoid eating or drinking anything (except water) for at least 8–12 hours before the test if instructed. If you’re on potassium supplements or medications, let your provider know beforehand.

What the Test Results Mean

Results are compared to a standard range, 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 and may require medical attention.

Common Conditions Linked to Potassium Imbalances

Chronic kidney disease, heart conditions (e.g., atrial fibrillation), or certain medications (like diuretics or steroids) can alter potassium levels. Symptoms like fatigue, cramps, or palpitations may signal imbalances.

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

Why might my potassium test be done regularly?
If you have a chronic condition like kidney disease, heart problems, or are taking medications that affect potassium (e.g., ACE inhibitors), your provider may monitor potassium levels regularly to prevent complications.
What does a ‘low potassium’ result mean?
A low potassium result suggests you may have lost too much potassium through vomiting, diarrhea, excessive sweating, or kidney issues. It can cause muscle weakness, irregular heartbeat, or fatigue. Your provider will determine the cause and recommend treatment, such as dietary changes or supplements.
Can diet affect potassium test results?
Yes, eating foods high in potassium (e.g., bananas, spinach, or nuts) may temporarily raise your potassium level. If your test is part of a routine check, avoid extreme dietary changes before the test to get an accurate reading.
  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