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Potassium in Serum (or Plasma) Concentration

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

This test measures the amount of potassium, a mineral essential for heart function 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
2828-2
Short code
Potassium Ur-sCnc
Synonyms
Potassium Ur-sCnc
Category
electrolyte
Sample
urine
Container
Sterile urine container
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
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to check for low or high potassium levels, which can affect heart rhythm, muscle function, or other body processes. It’s often done if you have symptoms like muscle weakness, irregular heartbeat, or kidney issues, or if you’re taking medications that affect potassium levels.

What to Expect Before the Test

No special preparation is needed for this test. You’ll have a small needle inserted into a vein (usually in your arm), and a blood sample will be drawn. It usually takes a few minutes. If you’re tested for potassium in urine, you may need to collect a sample over a 24-hour period.

What Happens During the Test?

The blood sample (or urine sample, if applicable) is sent to a lab where it’s analyzed to measure potassium concentration. Results are typically available within 1–2 days.

What the Results Mean

Low potassium (hypokalemia) or high potassium (hyperkalemia) can cause serious health issues. Your doctor will interpret results in relation to your overall health and symptoms. They may also compare results with previous tests if applicable.

Reference range

Adult: 3.5-5.0 mmol/LN/A

Specimen: urine

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 Level

Frequently asked questions

What Are Common Causes of Abnormal Results?
Abnormal potassium levels can result from conditions like kidney disease, heart problems, vomiting, diarrhea, or certain medications (e.g., diuretics, heart medications). Low potassium may also occur from excessive sweating or poor diet.
How Often Should I Get This Test?
Your doctor will determine how often you need this test based on your health status, medications, and symptoms. Regular monitoring may be needed if you have chronic conditions like kidney disease or heart rhythm disorders.
Can I Eat or Drink Before the Test?
For blood potassium tests, you can eat and drink normally. For 24-hour urine tests, follow your doctor’s instructions regarding fluid and food intake to ensure accurate results.
  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