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Potassium concentration in serum/plasma

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

This test measures the amount of potassium, a mineral essential for heart function, muscle contractions, and nerve signaling, 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
22760-3
Short code
Potassium SerPl-mCnc
Synonyms
Potassium SerPl-mCnc
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 low (hypokalemia) or high (hyperkalemia) potassium levels, which can cause symptoms like muscle weakness, irregular heartbeat, or fatigue. It’s often done when you have symptoms like nausea, muscle cramps, or irregular heartbeat, or if you’re taking certain medications that affect potassium levels, such as diuretics or certain heart medications.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for a few hours before the test, but this depends on your doctor’s instructions. Bring any medications you’re currently taking, as they can affect results.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. The blood sample is then sent to a lab for analysis. The test typically takes a few minutes, and you may feel a slight pinch or discomfort during the draw.

What Do the Results Mean?

Results are compared to a standard range for healthy adults. Low potassium levels may indicate conditions like kidney problems, vomiting, or certain medications. High levels can be linked to kidney failure, severe dehydration, or certain medical conditions or medications.

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/plasma potassium

Frequently asked questions

What causes potassium levels to be too low or too high?
Low potassium levels (hypokalemia) can result from conditions like vomiting, diarrhea, excessive sweating, kidney problems, or certain medications (e.g., diuretics). High potassium levels (hyperkalemia) may be caused by kidney failure, severe dehydration, certain medications (e.g., ACE inhibitors), or conditions like adrenal insufficiency.
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 underlying conditions. Regular monitoring may be recommended if you have chronic conditions like heart disease, kidney disease, or diabetes, or if you’re on medications that affect potassium levels.
Can food or medications affect potassium test results?
Some foods, like bananas, potatoes, and spinach, are high in potassium and may influence results if eaten in large amounts before testing. Certain medications, such as diuretics or heart medications, can also affect potassium levels and may require your doctor’s knowledge before testing.
  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