{
  "id": "corrected-calcium",
  "version": "cdcc703f2345",
  "status": "published",
  "name": "Corrected Calcium Calculator",
  "question": "What is corrected calcium?",
  "summary": "Adjusts total serum calcium for a low or high albumin: corrected calcium = total calcium + 0.8 × (normal albumin − albumin), in mg/dL and g/dL, or any other unit.",
  "category": "health",
  "subcategory": "clinical",
  "url": "https://www.acalculator.org/health/corrected-calcium-score-calculator",
  "markdown": "https://www.acalculator.org/health/corrected-calcium-score-calculator.md",
  "kind": "formulas",
  "method": "corrected calcium (mg/dL) = total calcium (mg/dL) + 0.8 × (normal albumin (g/dL) − albumin (g/dL))",
  "assumptions": [
    "The factor is 0.8 mg/dL of calcium per 1 g/dL of albumin (Merck Manual). Other units are converted to mg/dL and g/dL first; mmol/L uses the calcium molar mass 40.078 g/mol.",
    "Normal albumin defaults to 4.0 g/dL (40 g/L), the value in Payne et al. (1973).",
    "The normal range shown is the Merck Manual adult total serum calcium range, 8.8 to 10.4 mg/dL (2.20 to 2.60 mmol/L). Labs set their own ranges."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "calcium": {
        "title": "Total calcium",
        "description": "Total serum calcium from the blood test.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "concentration",
        "exclusiveMinimum": 0,
        "maximum": 1
      },
      "alb": {
        "title": "Albumin",
        "description": "Serum albumin from the same blood test.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "concentration",
        "exclusiveMinimum": 0,
        "maximum": 100
      },
      "normalAlb": {
        "title": "Normal albumin",
        "description": "The albumin level the correction assumes is normal, usually 4.0 g/dL (40 g/L).",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "concentration",
        "exclusiveMinimum": 0,
        "maximum": 100
      },
      "corrected": {
        "title": "Corrected calcium",
        "description": "Total calcium adjusted to a normal albumin level.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "concentration",
        "exclusiveMinimum": 0,
        "maximum": 1
      }
    }
  },
  "solve": {
    "fillAny": 3,
    "variables": [
      "calcium",
      "alb",
      "normalAlb",
      "corrected"
    ],
    "inputsOnly": []
  },
  "outputs": {
    "total": {
      "label": "Total calcium",
      "description": "Total serum calcium from the blood test.",
      "format": "quantity"
    },
    "albumin": {
      "label": "Albumin",
      "description": "Serum albumin from the same blood test.",
      "format": "quantity"
    },
    "normalAlbumin": {
      "label": "Normal albumin",
      "description": "The albumin level the correction assumes is normal, usually 4.0 g/dL (40 g/L).",
      "format": "quantity"
    },
    "corrected": {
      "label": "Corrected calcium",
      "description": "Total calcium adjusted to a normal albumin level.",
      "format": "quantity",
      "unit": "mg-dL"
    },
    "correctedMmol": {
      "label": "Corrected calcium (mmol/L)",
      "description": "The corrected calcium in millimoles per litre: g/L ÷ 40.078 g/mol × 1,000.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "calcium": 0.095,
      "alb": 40,
      "normalAlb": 40
    },
    "outputs": {
      "corrected": 0.095,
      "correctedMmol": 2.370377763361445
    },
    "text": "With albumin 4 g/dL, a total calcium of 9.5 mg/dL corrects to 9.5 mg/dL."
  },
  "examples": [
    {
      "given": {
        "calcium": 0.095,
        "alb": 40,
        "normalAlb": 40
      },
      "expect": {
        "corrected": 0.095
      },
      "source": "Merck Manual: no correction when albumin is 4.0 g/dL; 9.5 mg/dL is inside 8.8 to 10.4 (values in g/L); Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. https://doi.org/10.1136/bmj.4.5893.643"
    },
    {
      "given": {
        "calcium": 0.076,
        "alb": 20,
        "normalAlb": 40
      },
      "expect": {
        "corrected": 0.092
      },
      "source": "Merck Manual, Hypocalcemia: albumin 2.0 g/dL lowers calcium by about 1.6 mg/dL; 7.6 + 0.8 × (4.0 − 2.0) = 9.2 mg/dL = 0.092 g/L; Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. https://doi.org/10.1136/bmj.4.5893.643",
      "tolerance": 1e-12
    },
    {
      "given": {
        "calcium": 0.080156,
        "alb": 25,
        "normalAlb": 40
      },
      "expect": {
        "corrected": 0.092156,
        "correctedMmol": 2.299416138529867
      },
      "source": "hand calculation in content.mdx: 2.00 mmol/L × 40.078 g/mol = 0.080156 g/L; + 0.0008 × (40 − 25) = 0.092156 g/L = 2.2994 mmol/L; Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. https://doi.org/10.1136/bmj.4.5893.643",
      "tolerance": 1e-12
    },
    {
      "given": {
        "calcium": 0.08,
        "corrected": 0.09,
        "normalAlb": 40
      },
      "expect": {
        "alb": 27.5
      },
      "source": "hand calculation in content.mdx: albumin = 4.0 − (9.0 − 8.0) ÷ 0.8 = 2.75 g/dL = 27.5 g/L; Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. https://doi.org/10.1136/bmj.4.5893.643",
      "tolerance": 1e-12
    }
  ],
  "sources": [
    "Merck Manual Professional Version, Hypocalcemia: measured total serum calcium changes by about 0.8 mg/dL (0.2 mmol/L) for every 1 g/dL change in albumin. https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/electrolyte-disorders/hypocalcemia",
    "Merck Manual Professional Version, Overview of Disorders of Calcium Concentration: normal total serum calcium 8.8 to 10.4 mg/dL (2.20 to 2.60 mmol/L). https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/electrolyte-disorders/overview-of-disorders-of-calcium-concentration",
    "Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. https://doi.org/10.1136/bmj.4.5893.643",
    "IUPAC CIAAW, abridged standard atomic weights (2021): calcium 40.078. https://ciaaw.org/abridged-atomic-weights.htm"
  ],
  "related": [],
  "changelog": [
    {
      "date": "2026-09-28",
      "note": "Metric keeps calcium in mg/dL instead of mg/L."
    },
    {
      "date": "2026-09-29",
      "note": "Worked examples name a published reference for their rule."
    }
  ]
}