Corrected Calcium Calculator
Albumin-corrected total calcium in mg/dL or mmol/L.
Corrected calcium (mg/dL) = measured calcium + 0.8 × (4.0 − albumin in g/dL). In SI units: corrected calcium (mmol/L) = measured calcium + 0.02 × (40 − albumin in g/L). It estimates what total calcium would be if albumin were normal; ionized calcium is more accurate.
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How to use it
- Pick mg/dL or mmol/L units.
- Enter total calcium and serum albumin; change the normal albumin if your lab uses a different value.
- Read the corrected calcium and where it falls in the normal range.
What you enter
- Total serum calcium
- Serum albumin
- Normal albumin value (default 4.0 g/dL or 40 g/L)
What you get
- Albumin-corrected calcium
- Low, normal or high against the adult range
Formula
Ca(corrected, mg/dL) = Ca + 0.8 × (4.0 − albumin g/dL) | Ca(corrected, mmol/L) = Ca + 0.02 × (40 − albumin g/L)
About 40% of serum calcium is bound to albumin, so low albumin lowers total calcium without changing the active ionized fraction.
Worked example
Input: Calcium 8.2 mg/dL, albumin 2.8 g/dL
Result: Corrected calcium 9.2 mg/dL
The low total calcium is explained by low albumin; the corrected value is normal.
Questions
What is the corrected calcium formula?
Corrected calcium = total calcium + 0.8 × (4.0 − albumin), with calcium in mg/dL and albumin in g/dL. In SI units, add 0.02 × (40 − albumin in g/L) to calcium in mmol/L.
When should corrected calcium not be used?
It is unreliable in kidney failure, critical illness and acid-base disorders, and it is not recommended in dogs and cats. Measure ionized calcium when the result will change treatment.
What is a normal corrected calcium?
For adults, about 8.5–10.5 mg/dL (2.12–2.62 mmol/L), depending on the lab.
Limitations
- Poor agreement with ionized calcium in many patients.
- Not validated in dogs or cats; use ionized calcium.
References
- Payne RB, Little AJ, Williams RB, Milner JR (1973) British Medical Journal 4(5893):643-646.
- Schenck PA, Chew DJ (2005) American Journal of Veterinary Research 66(8):1330-1336.
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