Skip to content

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 and nerve signaling, in your blood.

Quick summary

["Potassium helps regulate muscle and nerve activity and supports overall heart health."]

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

Key facts at a glance

LOINC
12812-4
Short code
Potassium sp2 SerPl-sCnc
Synonyms
Potassium sp2 SerPl-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 low or high potassium levels, which can cause serious health issues like irregular heartbeat, muscle weakness, or fatigue. It’s often done when you have symptoms like muscle cramps, nausea, or unusual heart rhythms, or if you’re taking certain medications that affect potassium levels.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw blood. It usually takes a few minutes, and you may feel a slight pinch. If you’re on a low-potassium diet or taking potassium-sparing medications, let your doctor know before the test.

What the Results Mean

Results are compared to standard ranges for your age and health. Very high or very low potassium levels can indicate underlying health problems, such as kidney issues, heart conditions, or certain medications affecting electrolyte balance.

Common Causes of Abnormal Results

Low potassium (hypokalemia) can be caused by vomiting, diarrhea, excessive sweating, or certain medications. High potassium (hyperkalemia) may result from kidney problems, severe dehydration, or overuse of potassium supplements.

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 Potassium (K+)

Frequently asked questions

What symptoms might indicate I need this test?
Symptoms like muscle weakness, irregular heartbeat, or unexplained fatigue could signal potassium imbalances. Your doctor may also order this test if you have conditions like heart disease, kidney problems, or are taking medications that affect potassium levels, such as diuretics or certain blood pressure drugs.
How often should I get this test?
The frequency depends on your health status. If you have chronic conditions like kidney disease or heart problems, your doctor may recommend regular monitoring. Otherwise, this test is usually done only when needed for diagnosis or management of symptoms.
Can diet affect potassium levels?
Yes, diet plays a role. Foods high in potassium, like bananas, spinach, and potatoes, can raise potassium levels. Conversely, diets low in potassium, such as very low-sodium or strict low-potassium diets, may lower it. Always follow your doctor’s advice regarding diet and supplements.
  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