Corrected Calcium Calculator

Adjust serum calcium for albumin levels to accurately assess true calcium status in patients with hypoalbuminemia.

Quick Reference

Normal Calcium
8.5 - 10.5 mg/dL
2.12 - 2.62 mmol/L
Normal Albumin
3.5 - 5.0 g/dL
35 - 50 g/L
Correction Factor
0.8 mg/dL
per 1 g/dL albumin below 4.0
Reference Albumin
4.0 g/dL
Standard reference value

Results

Calculated
Corrected Calcium
--
mg/dL
Measured Calcium
--
mg/dL
Correction Applied
--
mg/dL

Clinical Interpretation

Understanding Corrected Calcium

About 40% of total serum calcium is bound to albumin. When albumin levels are low (hypoalbuminemia), total calcium may appear falsely low even when the physiologically active ionized calcium is normal. The corrected calcium formula adjusts for this protein binding effect.

Correction Formula

Corrected Ca (mg/dL) = Measured Ca + 0.8 x (4.0 - Albumin)

Where Albumin is in g/dL and 4.0 g/dL is the normal reference value

For every 1 g/dL decrease in albumin below 4.0 g/dL, add 0.8 mg/dL to the measured calcium.

Normal Calcium Ranges

Categorymg/dLmmol/L
Low (Hypocalcemia)< 8.5< 2.12
Normal8.5 - 10.52.12 - 2.62
High (Hypercalcemia)> 10.5> 2.62

When to Use Corrected Calcium

  • Patients with hypoalbuminemia (albumin < 4 g/dL)
  • Chronic kidney disease
  • Liver cirrhosis
  • Malnutrition
  • Nephrotic syndrome
  • Critical illness
  • Malignancy

Causes of Hypocalcemia

  • Hypoparathyroidism
  • Vitamin D deficiency
  • Chronic kidney disease
  • Pancreatitis
  • Hypomagnesemia
  • Medications (bisphosphonates, loop diuretics)
  • Post-thyroidectomy

Causes of Hypercalcemia

  • Primary hyperparathyroidism (most common outpatient)
  • Malignancy (most common inpatient)
  • Vitamin D toxicity
  • Thiazide diuretics
  • Granulomatous diseases
  • Hyperthyroidism
  • Immobilization

Symptoms of Calcium Imbalance

Hypocalcemia

  • Muscle cramps and spasms
  • Numbness and tingling (perioral, fingers, toes)
  • Chvostek's sign, Trousseau's sign
  • Seizures
  • QT prolongation on ECG

Hypercalcemia

  • "Stones" - kidney stones
  • "Bones" - bone pain
  • "Groans" - abdominal pain, constipation
  • "Moans" - fatigue, depression, confusion
  • Polyuria, polydipsia
  • Short QT on ECG

Limitations

  • Correction formula is an estimate; ionized calcium is more accurate
  • May be inaccurate in severe acid-base disturbances
  • Different laboratories may use different correction factors
  • Less reliable in hyperalbuminemia

Medical Disclaimer

This calculator is provided for educational and informational purposes only. It should not be used as a substitute for clinical judgment or professional medical advice. For accurate assessment of calcium status, especially in critically ill patients, ionized calcium measurement is preferred. Always consult with a qualified healthcare provider for medical decisions.