{
  "slug": "corrected-calcium",
  "title": "Corrected Calcium Calculator (Albumin-Adjusted)",
  "heading": "Corrected Calcium Calculator",
  "category": "fitness-health",
  "url": "https://www.revenuelab.fyi/toolbox/corrected-calcium",
  "summary": "Adjust total serum calcium for low albumin using the Payne formula.",
  "description": "Total serum calcium is roughly 40% protein-bound, mostly to albumin, so a low albumin makes total calcium read low even when the physiologically active ionized fraction is normal. The Payne correction adds 0.8 mg/dL to measured calcium for every 1 g/dL that albumin sits below 4.0 g/dL, giving a corrected value that better reflects true calcium status without drawing an ionized calcium. It is widely used at the bedside because it needs only two common labs and no extra blood draw. It is an estimate, not a replacement for ionized calcium in critically ill, dialysis, or acid-base-abnormal patients, where the relationship between albumin and ionized calcium breaks down. Use corrected calcium to decide whether a \"low\" total calcium warrants workup, and confirm any borderline or clinically important result with a directly measured ionized calcium. This tool is for education and workflow support only — not medical advice. Always verify results with a clinician and use clinical judgment alongside your institution's protocols.",
  "formula": "Corrected Ca (mg/dL) = measured Ca + 0.8 × (4.0 − albumin g/dL).",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=corrected-calcium",
  "inputs": [
    {
      "id": "ca",
      "label": "Measured total calcium",
      "kind": "number",
      "hint": null,
      "default": 8.2,
      "unit": "mg/dL",
      "min": 4,
      "max": 16
    },
    {
      "id": "albumin",
      "label": "Serum albumin",
      "kind": "number",
      "hint": null,
      "default": 2.5,
      "unit": "g/dL",
      "min": 0.5,
      "max": 5.5
    }
  ],
  "outputs": [
    {
      "id": "corrected",
      "label": "Corrected calcium",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "delta",
      "label": "Adjustment applied (mg/dL)",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "status",
      "label": "Interpretation",
      "format": "raw",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Measured total calcium: 8.2 mg/dL",
      "Serum albumin: 2.5 g/dL"
    ],
    "outputs": [
      "Corrected calcium: 9.4",
      "Adjustment applied (mg/dL): 1.2",
      "Interpretation: Normal range"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter measured total calcium (mg/dL).",
      "Enter serum albumin (g/dL).",
      "Read your corrected calcium on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "ca": 4.919999999999999,
        "albumin": 1.5
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "ca": 8.2,
        "albumin": 2.5
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "ca": 13.12,
        "albumin": 4
      }
    }
  ],
  "limitations": [
    "Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.",
    "Results do not account for medical conditions, medication, or pregnancy.",
    "Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it."
  ],
  "faq": [
    {
      "q": "When should I use ionized calcium instead?",
      "a": "Order ionized calcium directly in critically ill patients, dialysis patients, those with significant acid-base disturbance, or anyone with a liver disease severe enough to distort albumin-bound calcium behavior. The Payne correction assumes a fairly stable relationship between albumin and protein binding that these situations violate, so a corrected value can mislead you exactly when precision matters most."
    },
    {
      "q": "Why does albumin change the calcium reading at all?",
      "a": "Lab assays measure total calcium, which includes calcium bound to albumin, calcium bound to other anions, and free ionized calcium. Only the ionized fraction is biologically active. When albumin drops, less calcium is bound, so total calcium falls even though ionized calcium — the part your body actually uses — may be unchanged."
    },
    {
      "q": "Is 0.8 the only correction factor used?",
      "a": "Some references use 0.8 mg/dL per g/dL of albumin deficit (the Payne formula shown here); others use 0.7 or 0.9 depending on institution. The differences are small in most clinical scenarios, but if your lab or hospital protocol specifies a different factor, use that one for consistency with prior results."
    },
    {
      "q": "What counts as a normal corrected calcium?",
      "a": "Most labs report normal total calcium as roughly 8.5–10.5 mg/dL, and the corrected value is interpreted against that same range. Values outside that band, especially with symptoms like tetany, confusion, kidney stones, or arrhythmia, warrant a full metabolic panel and possibly parathyroid hormone testing."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/osmolar-gap",
    "https://www.revenuelab.fyi/toolbox/fena-calculator",
    "https://www.revenuelab.fyi/toolbox/abg-interpretation"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Corrected Calcium Calculator (Albumin-Adjusted) (https://www.revenuelab.fyi/toolbox/corrected-calcium)"
}