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Potassium in Serum (Fluid) Concentration

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

This test measures the amount of potassium, a mineral essential for heart function and muscle activity, 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
2821-7
Short code
Potassium Fld-sCnc
Synonyms
Potassium Fld-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 your heart, kidneys, or digestive system, or to monitor treatment for conditions like heart failure, kidney disease, or certain medications that alter potassium levels.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for a few hours before the blood draw if your doctor specifies. Stay hydrated unless instructed otherwise.

How the Test Is Performed

A healthcare provider will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but the procedure is quick and usually painless.

Possible Results and Normal Values

Results are compared to standard reference ranges, but exact values can vary by lab. Abnormal results may signal conditions like low or high potassium levels, dehydration, or kidney issues.

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 is critical for nerve and muscle function, including your heart’s rhythm. Low potassium (hypokalemia) can cause muscle weakness, irregular heartbeats, or fatigue, while high potassium (hyperkalemia) may lead to heart problems, nausea, or muscle cramps. Your doctor will interpret results in the context of your overall health 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 from eating disorders or excessive use of laxatives.
What causes high potassium levels?
High potassium can be caused by kidney failure, severe dehydration, excessive potassium supplements, or certain medications (e.g., blood pressure drugs). It may also occur in conditions like Addison’s disease or untreated diabetes.
When should I worry about abnormal potassium levels?
If you experience symptoms like muscle weakness, irregular heartbeat, confusion, or severe nausea—especially if you have a history of heart issues—contact your doctor immediately. Abnormal results alone may not require urgent action unless your doctor advises otherwise.
  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