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Junctional Na+/K+ ATPase Activity (Serum)

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

This test measures the activity of the enzyme responsible for regulating sodium and potassium levels in your blood, which helps maintain fluid balance and nerve function.

Quick summary

["This test assesses how well your body regulates essential electrolytes through the sodium-potassium pump."]

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

Key facts at a glance

LOINC
18548-8
Short code
J Pnt ST Amp+20ms L-II
Synonyms
J Pnt ST Amp+20ms L-II
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
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 This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like muscle weakness, irregular heartbeat, or unexplained fluid imbalances. It can also be part of evaluating conditions affecting electrolyte balance, such as certain kidney disorders or heart conditions.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, typically drawn from a vein in your arm. Avoid excessive salt intake or diuretics for 24 hours before testing if instructed by your provider.

What the Results Mean

Lower than expected activity may indicate problems with the enzyme itself or conditions disrupting normal electrolyte function. Higher-than-expected levels could suggest metabolic disturbances or other underlying issues.

Common Conditions Monitored

This test helps diagnose or monitor conditions like pseudohypoaldosteronism, certain genetic disorders affecting sodium-potassium transport, or metabolic alkalosis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Sodium-Potassium Pump Activity

Frequently asked questions

How soon will I get my results?
Results are typically available within 1–3 business days, depending on lab processing times. Your healthcare provider will discuss them with you during your follow-up visit.
Can I eat or drink before this test?
Standard fasting is not required, but follow any specific instructions your provider gives you. Avoid alcohol or excessive salt intake for 24 hours if advised.
What if my results are abnormal?
If results are abnormal, your provider will work with you to determine the cause and next steps, which may include further testing or adjustments to your treatment plan.
  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