MedCalcHub stores your favorites, history, and saved calculations locally in your browser using localStorage. This data never leaves your device.
Optional advertising, when enabled, may use third-party cookies or similar technologies. You can accept or reject advertising below.
Calculates corrected total serum calcium adjusted for hypoalbuminemia. In hypoalbuminemia, measured total calcium is falsely low because less calcium is protein-bound; this correction estimates the physiologically active total calcium.
Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.
Total serum calcium exists in three fractions: protein-bound (mostly attached to albumin), complexed, and ionized (free) calcium, with the ionized fraction being the physiologically active form. Because roughly 40-50% of total calcium is bound to albumin, hypoalbuminemia lowers the measured total calcium even when ionized calcium is normal. This calculator applies the Payne correction (corrected calcium = measured total calcium + 0.8 x (4 - albumin)) to estimate the total calcium level expected at a normal albumin of 4.0 g/dL. The correction is an estimate, not a measurement. It assumes a fixed calcium-albumin binding relationship that varies across patients and becomes progressively less reliable at very low albumin concentrations and in states that alter protein binding, such as acid-base disturbances. The formula is not validated for every setting; it is especially unreliable when screening for hypercalcemia, and the corrected value should not replace ionized calcium measurement when the physiologically active fraction is needed, most notably in critically ill patients. Ionized calcium directly reflects the biologically active fraction and is unaffected by albumin concentration; it is the preferred test when a calcium-albumin binding artifact is suspected or when the clinical question concerns the active form. The corrected value is best used as a transitional estimate to interpret total calcium in patients with abnormal albumin while weighing whether a direct ionized measurement is required. Interpret the result together with total protein, pH, kidney function, and the clinical presentation. This is an educational decision-support estimate and does not by itself diagnose hypocalcemia or hypercalcemia.
Specialty
Internal MedicineCategory
LaboratoryDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-08-06
Formula
Keywords
Normal Range
8.5–10.5 mg/dL
| Classification | Range |
|---|---|
Hypocalcemia | <8.5 |
Normal corrected calcium | 8.5–10.5 |
Hypercalcemia | ≥10.6 |
Severe hypercalcemia | ≥12.5 |
Adjusts measured total serum calcium for hypoalbuminemia to estimate the physiologically relevant total calcium, since a large fraction of serum calcium is albumin-bound.
Corrected calcium = measured calcium + 0.8 x (4.0 - serum albumin), with calcium in mg/dL and albumin in g/dL. It estimates the calcium level expected if albumin were normal.
Measured total serum calcium in mg/dL.
Serum albumin in g/dL; each 1 g/dL below 4.0 adds 0.8 mg/dL to the corrected calcium.
Corrected calcium < 8.5 mg/dL indicates hypocalcemia, 8.5–10.5 mg/dL is normal, ≥ 10.6 mg/dL is hypercalcemia, and ≥ 12.5 mg/dL is severe hypercalcemia. The correction assumes a normal albumin of 4.0 g/dL and becomes less reliable when albumin is below 2.0 g/dL. In neonates and children, correction factors and reference ranges differ.
Because a large fraction of serum calcium is protein-bound, low albumin can mask true calcium status; correction helps avoid unnecessary treatment of spurious hypocalcemia.
A 63-year-old woman with cirrhosis has a measured total calcium of 8.0 mg/dL and serum albumin of 2.0 g/dL.
Inputs:
Expected Result: Corrected calcium = 8.0 + 0.8 × (4 − 2) = 9.6 mg/dL, within the normal range. The low measured calcium was explained by hypoalbuminemia.
About 40–50% of serum calcium is bound to albumin. When albumin is low (e.g. liver disease, nephrotic syndrome), total calcium appears falsely low even though ionized (biologically active) calcium may be normal. The correction factor estimates what total calcium would be at a normal albumin of 4.0 g/dL.
A corrected calcium > 10.5 mg/dL suggests true hypercalcemia. Common causes include primary hyperparathyroidism, malignancy, vitamin D toxicity, and granulomatous disease. Confirm with ionized calcium and investigate accordingly.
Yes. Ionized (free) calcium directly measures the physiologically active fraction and is not affected by albumin. It is the preferred test, but the correction is useful when ionized calcium measurement is unavailable.
The formula is validated in adults. Neonatal and paediatric reference ranges and correction factors differ; consult local guidelines for those populations.
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. The correction is an estimate; ionized calcium is the preferred measurement in the critically ill and when hypercalcemia is suspected.
Correcting total calcium in hypoalbuminemia.
Does not replace ionized calcium measurement.
Assessing vascular calcification risk in CKD.
Does not assess albumin or calcium correction.
CKD screening and staging.
Assesses albuminuria, not serum calcium status.