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Potassium (Serum) with Mass Concentration Measurement

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 serum.

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
111266-3
Short code
Potassium Msmt Stl
Synonyms
Potassium Msmt Stl
Category
electrolyte
Sample
stool
Container
Clean container
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 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for low (hypokalemia) or high (hyperkalemia) potassium levels, which can affect heart rhythm, muscle function, or kidney health. It’s often done when you have symptoms like muscle weakness, irregular heartbeat, or conditions like kidney disease or heart problems.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw if your test is part of a broader metabolic panel. Wear a loose shirt for easy access.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm to draw blood. You may feel a slight pinch, but it’s quick and painless. The blood sample is then sent to a lab for analysis.

What Are the Possible Results?

Results are typically reported in milliequivalents per liter (mEq/L). Abnormal levels may indicate underlying health issues that need further evaluation by your doctor.

Reference range

Adult: 3.5-5.0 mmol/LN/A

Specimen: stool

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

What causes potassium levels to be too low?
Potassium can drop due to conditions like vomiting, diarrhea, excessive sweating, or certain medications (e.g., diuretics). It may also occur in people with low magnesium or kidney problems, or those who don’t eat enough potassium-rich foods like bananas, potatoes, or spinach.
What causes potassium levels to be too high?
High potassium levels (hyperkalemia) can result from kidney failure, severe dehydration, or medications like ACE inhibitors or potassium-sparing diuretics. It may also occur in people with adrenal insufficiency or untreated diabetes.
How often should I get this test?
Your doctor will determine how often you need this test based on your health status, medications, and any ongoing conditions. Regular monitoring may be recommended if you have chronic kidney disease, heart problems, or take medications that affect potassium levels.
  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