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Potassium ion concentration in serum/plasma (mass concentration)

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 help assess heart health, muscle function, and fluid balance in your body."]

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

Key facts at a glance

LOINC
4380-2
Short code
Penicillin G Potassium Dose
Synonyms
Penicillin G Potassium Dose
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 like low potassium (hypokalemia), high potassium (hyperkalemia), or kidney problems. It can also be done during monitoring for heart conditions, dehydration, or certain medications.

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 it’s part of a broader metabolic panel. Bring any medications you’re 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 that detects its concentration in the blood.

What the Results Mean

Results are compared to standard reference ranges, but exact values can vary by lab. Low potassium may cause muscle weakness or irregular heartbeat, while high potassium can be dangerous for the heart.

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

What causes low potassium levels?
Low potassium (hypokalemia) 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.
What causes high potassium levels?
High potassium (hyperkalemia) can be caused by kidney failure, severe dehydration, certain medications (e.g., blood pressure drugs), or untreated diabetes. It’s especially dangerous if it affects heart function.
How often should I get this test?
Your doctor will determine how often you need this test based on your health status, symptoms, or ongoing treatments. Regular monitoring may be recommended if you have conditions like heart disease, kidney issues, 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