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Potassium concentration in serum/plasma

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 is essential for heart health and muscle function, and levels can be influenced by diet, medications, and kidney function."]

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

Key facts at a glance

LOINC
49788-3
Short code
Potassium Amn-sCnc
Synonyms
Potassium Amn-sCnc
Category
electrolyte
Sample
fluid
Container
Sterile tube
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
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for conditions like low potassium (hypokalemia) or high potassium (hyperkalemia), which can cause muscle weakness, irregular heartbeat, or other symptoms. It may also be done to monitor kidney function, acid-base balance, or response to certain treatments.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood draw from a vein in your arm. If you’re on certain medications or have kidney issues, let your provider know.

What the Results Mean

Results are typically reported in millimoles per liter (mmol/L). While reference ranges vary by lab, abnormal levels may signal underlying health concerns requiring further evaluation.

Common Causes of Abnormal Results

Low potassium levels (hypokalemia) can occur from vomiting, diarrhea, excessive sweating, or certain medications. High potassium levels (hyperkalemia) may result from kidney problems, severe dehydration, or medical conditions like diabetes.

Reference range

Adult: 3.5-5.0 mmol/LN/A

Specimen: fluid

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Serum Potassium (K+)

Frequently asked questions

What symptoms might indicate low potassium?
Symptoms of low potassium may include muscle cramps, fatigue, irregular heartbeat, or weakness. If you experience these, discuss them with your doctor.
What symptoms might indicate high potassium?
High potassium can cause muscle weakness, numbness, or irregular heartbeat. Seek medical attention if you notice these signs, especially if you have kidney problems.
Does diet affect potassium levels?
Yes, foods high in potassium (like bananas, spinach, or potatoes) can influence your levels. If you’re on a low-potassium diet, your provider may recommend monitoring 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