Corrected Calcium Calculator
Calculate corrected calcium level to account for low or high albumin levels, providing accurate calcium assessment in various medical conditions.
Why do we need to correct calcium for albumin?
About 40% of serum calcium is bound to albumin. When albumin is low (malnutrition, liver disease, nephrotic syndrome), total calcium appears falsely low, but ionized (free) calcium may be normal. Corrected calcium estimates true calcium status by adjusting for albumin level. Formula: Corrected Ca = Measured Ca + 0.8 * (4 - Albumin). For every 1 g/dL albumin drops below 4, calcium decreases ~0.8 mg/dL. Only ionized calcium is physiologically active.
When should I use corrected calcium instead of measured?
Use corrected calcium when: Albumin abnormal (<3.5 or >5 g/dL), assessing hypocalcemia/hypercalcemia in hypoalbuminemia, liver disease, malnutrition, nephrotic syndrome, critical illness. Best practice: measure ionized calcium directly when available (most accurate). Don't correct if albumin normal (3.5-5.5 g/dL). Corrected calcium is estimate; ionized calcium is gold standard for clinical decisions in unstable patients.
What is the normal corrected calcium range?
Normal total/corrected calcium: 8.5-10.5 mg/dL (some labs 8.4-10.2). Hypocalcemia: <8.5 mg/dL (mild 8-8.5, moderate 7-8, severe <7). Hypercalcemia: >10.5 mg/dL (mild 10.5-12, moderate 12-14, severe >14). Ionized calcium normal: 4.5-5.3 mg/dL or 1.1-1.3 mmol/L. Symptoms depend on severity and acuity. Severe hypocalcemia (<7) or hypercalcemia (>14) are medical emergencies requiring immediate treatment.
What causes hypocalcemia and how is it treated?
Causes: Hypoparathyroidism (post-thyroid surgery, autoimmune), vitamin D deficiency, chronic kidney disease, hypomagnesemia, acute pancreatitis, hungry bone syndrome. Symptoms: Paresthesias, muscle cramps, tetany, Chvostek/Trousseau signs, seizures, prolonged QT. Treatment: Mild - oral calcium + vitamin D; Severe/symptomatic - IV calcium gluconate, treat underlying cause, check magnesium (hypoMg prevents Ca correction). Chronic - calcium supplements, vitamin D, treat CKD.
What are the limitations of corrected calcium formula?
Limitations: Only estimates ionized calcium, doesn't account for pH (alkalosis increases binding, decreases ionized Ca; acidosis opposite), assumes normal protein binding, inaccurate in critical illness with acid-base disturbances, less reliable when albumin <2 g/dL. Multiple correction formulas exist with slight variations. Best approach: measure ionized calcium directly when clinical decision critical (ICU, surgery, parathyroid disorders). Use corrected calcium as screening tool only.