Serum Electrolytes (Na / K / Cl)
What Is This Test?
The Serum Electrolytes test is a blood test that measures the levels of the body's major electrolytes:
- Sodium (Na⁺)
- Potassium (K⁺)
- Chloride (Cl⁻)
Electrolytes are essential minerals that help regulate fluid balance, blood pressure, nerve function, muscle contraction, heart rhythm, and acid-base balance. This test helps diagnose electrolyte imbalances caused by dehydration, kidney disease, heart disease, hormonal disorders, and certain medications.
Why this test is performed?
Doctors may recommend the Serum Electrolytes test to:
- Evaluate dehydration or overhydration
- Assess kidney function
- Monitor heart diseases
- Diagnose electrolyte imbalances
- Investigate muscle weakness or cramps
- Evaluate irregular heartbeat (arrhythmia)
- Monitor patients receiving intravenous (IV) fluids
- Assess high blood pressure
- Evaluate endocrine disorders (such as adrenal gland disorders)
- Monitor patients taking diuretics or other medications affecting electrolyte balance
Test Preparation
Fasting is generally not required.
Drink water normally unless your doctor advises otherwise.
Inform your healthcare provider about all medications, especially:
- Diuretics (water pills)
- Blood pressure medications
- Potassium supplements
- Steroids
- Laxatives
Avoid strenuous exercise immediately before the test, as it may temporarily affect potassium levels.
Medical disclaimer
This article is for general information and education only. It is not medical advice, does not create a doctor–patient relationship, and is not a substitute for consultation with a qualified doctor who has assessed your individual situation. Never delay seeking medical advice because of something you have read here.
In a medical emergency, call 112, or 108 for an ambulance where that service operates, or go to your nearest emergency department. If you are in mental health distress, Tele-MANAS is free and available 24×7 on 14416.
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