Description
An ionized calcium test measures the free, biologically active form of calcium in your blood. Unlike total calcium, which includes calcium bound to proteins (like albumin), ionized calcium represents the fraction that is physiologically active and essential for many body functions.
Why the Test Is Ordered
- Assess calcium metabolism: Provides a more accurate picture of calcium status than total calcium, especially in critically ill patients.
- Evaluate parathyroid function: Helps diagnose hyperparathyroidism or hypoparathyroidism.
- Monitor kidney function: Calcium levels can be affected by chronic kidney disease or dialysis.
- Detect electrolyte imbalances: Important for patients with acid-base disorders, severe illness, or those receiving blood transfusions.
- Monitor calcium in critically ill patients: Ionized calcium is often tested in ICU settings because it reflects immediate physiological calcium availability.
Symptoms or Conditions That May Prompt Testing
- Tingling or numbness in fingers or around the mouth
- Muscle cramps or spasms
- Fatigue, confusion, or irritability
- Bone pain or weakness
- Heart rhythm abnormalities
How the Test Works
- A blood sample is drawn and kept anaerobic (without exposure to air) because ionized calcium levels can change if the sample is exposed to air.
- The test measures the free calcium ions, providing an accurate assessment of biologically active calcium.
Interpretation of Results
- Low ionized calcium (hypocalcemia) may indicate:
- Hypoparathyroidism
- Vitamin D deficiency
- Kidney disease
- Severe illness or sepsis
- High ionized calcium (hypercalcemia) may indicate:
- Hyperparathyroidism
- Cancer
- Excessive vitamin D or calcium intake
- Certain endocrine disorders
Fasting Requirements
- Fasting is not required, but samples should be handled carefully to maintain accuracy.
The ionized calcium test is a critical tool for evaluating calcium-related disorders and provides a direct measurement of the calcium available for nerve, muscle, and bone function.
