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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 normal heart rhythm, muscle function, and nerve signaling, in your blood.

Quick summary

["Potassium levels help ensure your body’s electrical balance and muscle function work properly."]

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

Key facts at a glance

LOINC
77142-8
Short code
Potassium SerPlBld-sCnc
Synonyms
Potassium SerPlBld-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 issues, or certain medications that alter potassium levels. It’s also used to monitor patients with conditions like high blood pressure, heart failure, or those on diuretics.

What to Expect Before the Test

No special preparation is needed, but avoid eating or drinking anything (except water) for at least 8–12 hours before the test if instructed by your provider. Bring any medications you’re currently taking.

How the Test Is Performed

A blood sample is drawn from a vein, usually in your arm, by a healthcare professional. The sample is sent to a lab for analysis.

Possible Results and Interpretation

Results are compared to standard reference ranges for your age, gender, and overall health. Low potassium (hypokalemia) or high potassium (hyperkalemia) may signal underlying health 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.

Potassium levels are critical for heart function, muscle contractions, and nerve signaling. Abnormal levels can cause symptoms like weakness, irregular heartbeat, or muscle cramps. Your doctor will discuss results in the context of your medical history and symptoms.

Short name

Serum Potassium

Frequently asked questions

What causes low potassium levels?
Low potassium can result from conditions like vomiting, diarrhea, excessive sweating, kidney problems, or certain medications (e.g., diuretics). 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 conditions like Addison’s disease. It can also occur if you’re retaining too much salt or have untreated diabetes.
How is potassium imbalance treated?
Treatment depends on the cause and severity. Low potassium may be addressed with dietary changes or supplements, while high potassium often requires medical interventions like IV fluids, medications, or dialysis if kidneys are severely impaired.
  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