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Potassium in Serum or Plasma (Mass Concentration)

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

This test measures the amount of potassium, a mineral essential for heart function and nerve signaling, found in your blood.

Quick summary

["Potassium levels help assess heart health and balance of electrolytes in your body."]

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

Key facts at a glance

LOINC
51618-7
Short code
Potassium pre dial SerPl-sCnc
Synonyms
Potassium pre dial SerPl-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 doctor may order this test to check for conditions affecting potassium balance, such as kidney problems, heart rhythm issues, or certain medications that alter potassium levels. It can also be part of routine monitoring for people with chronic illnesses like diabetes or heart disease.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a metabolic panel. Avoid taking potassium supplements or certain medications (like some heart or blood pressure drugs) for 24 hours beforehand if instructed.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. The blood sample is sent to a lab, where it’s analyzed to measure potassium concentration. The result is typically available within 1–2 days.

What the Results Mean

Results are compared to a reference range specific to your lab, which accounts for factors like age, sex, and health status. Low potassium (hypokalemia) or high potassium (hyperkalemia) can signal underlying health concerns that need further evaluation.

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

What causes low potassium levels?
Low potassium can result from vomiting, diarrhea, excessive sweating, certain medications (like diuretics), kidney problems, or conditions like diabetes or low blood pressure.
What causes high potassium levels?
High potassium is often linked to kidney failure, severe dehydration, uncontrolled diabetes, or medications that affect kidney function or potassium excretion.
Can diet affect potassium levels?
Yes, diets high in potassium (e.g., bananas, spinach, nuts) or low in potassium (e.g., excessive salt intake) can influence results. Always follow your doctor’s advice on dietary restrictions related to this test.
  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