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Corrected Calcium Calculator
Approximately 40-45% of total calcium in the blood is bound to proteins, primarily albumin. Routine blood tests measure “Total Calcium,” which includes both bound and unbound forms.
In patients with hypoalbuminemia (low albumin), the Total Calcium level decreases even if the physiologically active (ionized) calcium remains normal. This calculator uses Payne’s Formula to correct the calcium level, preventing the misdiagnosis of hypocalcemia.
Laboratory Values
Inputsmg/dL
g/dL
Result
Normal Range: 8.5 – 10.5 mg/dL
Clinical Context
The Formula (Payne’s):
Corrected Ca = Total Ca + 0.8 × (4.0 − Serum Albumin)
Why it matters:
• Hypoalbuminemia: Common in liver disease, malnutrition, nephrotic syndrome, and chronic illness. Without correction, these patients may appear hypocalcemic when they are actually normocalcemic.
• Hypercalcemia: A patient with high albumin (rare, e.g., severe dehydration) might have a high total calcium but normal ionized calcium. Conversely, a patient with high total calcium AND low albumin has significant hypercalcemia that is worse than the uncorrected lab value suggests.
Clinical References
How to Use This Calculator
Follow these steps to calculate the albumin-corrected calcium.
Enter Total Calcium
Input the Total Calcium level from the metabolic panel (CMP/BMP) in mg/dL.
Enter Albumin
Input the serum Albumin level in g/dL.
Interpret Result
The corrected value appears. If the corrected calcium is normal (8.5–10.5), the patient likely has “pseudohypocalcemia” due to low albumin.
Frequently Asked Questions
No. Direct measurement of Ionized Calcium is the gold standard, but it is expensive and requires special handling. Corrected calcium is a useful estimation when ionized calcium testing is unavailable.
If albumin is 4.0 g/dL, the correction is zero. If albumin is > 4.0, the formula subtracts value, but clinicians often only apply it for hypoalbuminemia (< 4.0).