Calculate the albumin-corrected total calcium to avoid missing true hypocalcemia or hypercalcemia in hypoalbuminemia. Conventional formula (calcium mg/dL, albumin g/dL): Ca_corr = Ca + 0.8 × (4.0 − Albumin). SI formula (calcium mmol/L, albumin g/L): Ca_corr = Ca + 0.02 × (40 − Albumin). Roughly 40% of circulating calcium is albumin-bound, so low albumin lowers the measured total without changing the physiologically active ionized fraction. Corrected reference range ≈ 8.5–10.5 mg/dL (2.15–2.60 mmol/L). Low → true hypocalcemia (hypoparathyroidism, vitamin-D deficiency, CKD, hypomagnesemia, citrated transfusion, pancreatitis, sepsis); high → true hypercalcemia (primary hyperparathyroidism, malignancy/PTHrP, myeloma, vitamin-D intoxication, thiazides, immobilization, granulomatous disease). When albumin is markedly abnormal or acid-base is deranged, ionized calcium remains the gold standard. Based on Payne BMJ 1973 and MDCalc. Not medical advice.
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Key facts
Category
Health
Input types
select, number
Output type
json
Sample coverage
4
API ready
Yes
Overview
The Corrected Calcium (Albumin) Calculator estimates albumin-corrected total serum calcium from measured calcium and albumin values. Choose conventional or SI units to apply the corresponding Payne formula and receive a rounded result with a normal, low, or high category.
When to use
Use it when low albumin may be lowering measured total calcium without changing ionized calcium.
Result
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Use it to estimate whether a total calcium result remains within the corrected reference range of approximately 8.5–10.5 mg/dL or 2.15–2.60 mmol/L.
Use it for a quick calculation when laboratory values are reported in either conventional or SI units.
How it works
1Select Conventional units for calcium in mg/dL and albumin in g/dL, or SI units for calcium in mmol/L and albumin in g/L.
2Enter the measured total calcium and serum albumin values.
3The calculator applies Ca_corr = Ca + 0.8 × (4.0 − Albumin) for conventional units or Ca_corr = Ca + 0.02 × (40 − Albumin) for SI units.
4The result is rounded to the selected number of decimal places and categorized as corrected calcium low, normal, or high.
Use cases
Screening a low total calcium result for possible pseudo-hypocalcemia caused by hypoalbuminemia.
Checking calcium results in nephrology, endocrinology, and electrolyte review workflows.
Converting a laboratory calculation between conventional and SI reporting units.
Examples
1. Low albumin with normal corrected calcium
Clinician reviewing laboratory results
Background
A patient has a measured total calcium of 7.8 mg/dL and albumin of 2.5 g/dL.
Problem
Determine whether the low total calcium remains low after accounting for hypoalbuminemia.
How to use
Select Conventional units, enter calcium 7.8 and albumin 2.5, and keep decimal places at 2.