How to Calculate Corrected Calcium
What is Corrected Calcium?
Corrected calcium adjusts serum calcium for albumin levels, better reflecting true ionized calcium status and clinical significance.
Formula
Calculate: Corrected Ca = Measured Ca + 0.8 × (4.0 - Albumin)
- Ca
- Measured Ca + 0 — Measured Ca + 0
Step-by-Step Guide
- 1Calculate: Corrected Ca = Measured Ca + 0.8 × (4.0 - Albumin)
- 2Or use ionized calcium directly if available
- 3Normal corrected calcium 8.5-10.2 mg/dL
Worked Examples
Input
Total Ca 7.8 mg/dL, albumin 2.5 g/dL
Result
Corrected Ca = 7.8 + 0.8(4.0-2.5) = 9 mg/dL (normal)
Not hypocalcemic
Common Mistakes to Avoid
- ✕Forgetting albumin correction in hypoalbuminemic patients
- ✕Treating low total calcium as pathologic without correction
Frequently Asked Questions
Why adjust for albumin?
Albumin binds ~45% of serum calcium; low albumin falsely lowers total calcium without affecting ionized calcium.
When is correction unnecessary?
If ionized calcium is directly measured, no correction needed; it's the physiologically active form.
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