Serum Calcium
What Is This Test?
The Serum Calcium test is a blood test that measures the level of calcium in your bloodstream. Calcium is an essential mineral required for healthy bones and teeth, muscle contraction, nerve transmission, blood clotting, and proper heart function.
About 99% of the body's calcium is stored in bones and teeth, while the remaining 1% circulates in the blood. This test helps evaluate calcium balance and can assist in diagnosing bone disorders, kidney disease, parathyroid gland disorders, and vitamin D deficiency.
There are two main forms of calcium tests:
- Total Serum Calcium (most commonly performed)
- Ionized Calcium (measures the biologically active form of calcium)
Why this test is performed?
Doctors may recommend the Serum Calcium test to:
- Diagnose high or low calcium levels
- Evaluate bone disorders such as osteoporosis
- Assess parathyroid gland function
- Monitor Vitamin D deficiency
- Evaluate kidney disease
- Investigate abnormal heart rhythm
- Assess muscle cramps or spasms
- Monitor certain cancers affecting calcium levels
- Evaluate calcium metabolism disorders
- Monitor calcium supplementation therapy
Test Preparation
- Fasting is usually not required, although some laboratories may recommend 8–12 hours of fasting if other tests are being performed simultaneously.
- Drink water normally unless instructed otherwise.
- Inform your doctor about calcium supplements, Vitamin D supplements, antacids, or medications such as diuretics and lithium, as these may affect calcium levels.
- Avoid taking calcium supplements immediately before the test unless advised otherwise.
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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