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Potassium concentration in serum/plasma

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

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

Quick summary

["Potassium levels can affect heart health and muscle function—keep an eye on yours if you have symptoms like muscle weakness or irregular heartbeat."]

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

Key facts at a glance

LOINC
49789-1
Short code
Potassium Prt-sCnc
Synonyms
Potassium Prt-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?

Doctors may order a potassium test to check for conditions like low potassium (hypokalemia), high potassium (hyperkalemia), or kidney problems. It’s also used to monitor treatment for conditions like heart disease, diabetes, or certain medications.

What to Expect Before the Test

No special preparation is needed, but avoid eating or drinking for at least 8–12 hours before the test if instructed. Wear comfortable clothing and fasten your shirt for easy access to your arm.

What Happens During the Test?

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

What Are Common Results?

Results are reported in milliequivalents per liter (mEq/L). While reference ranges vary by lab, low potassium (below 3.5 mEq/L) or high potassium (above 5.0 mEq/L) may signal concerns.

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 (K+)

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–2 business days, depending on your lab’s processing time. Your doctor will discuss them with you during your follow-up visit.
What causes low potassium levels?
Low potassium can result from conditions like vomiting, diarrhea, excessive sweating, certain medications (e.g., diuretics), or kidney problems. It may also occur if you’re not eating enough potassium-rich foods like bananas, potatoes, or leafy greens.
What causes high potassium levels?
High potassium can be caused by kidney failure, severe dehydration, certain medications (e.g., blood pressure drugs), or untreated diabetes. It can also happen if you have a condition like Addison’s disease or excessive potassium intake from supplements.
  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