{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"corrected-calcium"},"result":{"entity_type":"calculator","id":"corrected-calcium","calculator_id":"corrected-calcium","canonical_url":"https://tttkmbb.com/medical/corrected-calcium","name":"Corrected Calcium Calculator","title":"Albumin-Corrected Calcium Calculator – Payne Formula (mg/dL and mmol/L)","category":"medical","category_name":"Medical & Clinical","tool_name":"calculate_corrected_calcium","featured_mcp_tool":false,"description":"Adjusts total serum calcium for low or high albumin with the Payne formula, in conventional (mg/dL, g/dL) or SI units (mmol/L, g/L), and reports both unit systems.","use_when":"You have a total calcium and albumin and want the albumin-adjusted calcium used to screen for hypo- or hypercalcaemia.","do_not_use_when":"An ionised calcium measurement is available (it is more accurate, especially in critical illness, acid-base disorders or renal failure).","inputs":[{"name":"calcium","label":"Total calcium","type":"number","required":true,"max":20,"exclusive_min":0,"description":"Measured total serum calcium in the unit system chosen below.","example":8},{"name":"albumin","label":"Albumin","type":"number","required":true,"max":70,"exclusive_min":0,"description":"Serum albumin: g/dL for the conventional system, g/L for SI.","example":2.5},{"name":"unit_system","label":"Unit system","type":"enum","required":false,"default":"conventional","values":[{"value":"conventional","label":"Calcium mg/dL, albumin g/dL","aliases":["mg_dl","mg/dl","us"]},{"value":"si","label":"Calcium mmol/L, albumin g/L","aliases":["mmol_l","mmol/l"]}],"description":"Units of the two inputs.","example":"conventional"}],"outputs":[{"name":"corrected_calcium","label":"Corrected calcium","type":"number","decimals":2,"description":"Albumin-corrected calcium in the input unit."},{"name":"corrected_calcium_mg_dl","label":"Corrected calcium","type":"number","unit":"mg/dL","decimals":2,"description":"Corrected calcium in mg/dL (mmol/L × 4.008)."},{"name":"corrected_calcium_mmol_l","label":"Corrected calcium","type":"number","unit":"mmol/L","decimals":2,"description":"Corrected calcium in mmol/L (mg/dL × 0.2495)."},{"name":"interpretation","label":"Interpretation","type":"string","decimals":4,"description":"Against a typical adult range of 8.5–10.5 mg/dL (2.12–2.62 mmol/L); laboratory ranges vary."}],"input_schema":{"type":"object","properties":{"calcium":{"description":"Measured total serum calcium in the unit system chosen below.","type":"number","maximum":20,"exclusiveMinimum":0,"examples":[8]},"albumin":{"description":"Serum albumin: g/dL for the conventional system, g/L for SI.","type":"number","maximum":70,"exclusiveMinimum":0,"examples":[2.5]},"unit_system":{"description":"Units of the two inputs.","type":"string","enum":["conventional","si"],"default":"conventional","examples":["conventional"]}},"additionalProperties":false,"required":["calcium","albumin"]},"output_schema":{"type":"object","properties":{"corrected_calcium":{"description":"Albumin-corrected calcium in the input unit.","type":"number"},"corrected_calcium_mg_dl":{"description":"Corrected calcium in mg/dL (mmol/L × 4.008). Unit: mg/dL.","type":"number","x-unit":"mg/dL"},"corrected_calcium_mmol_l":{"description":"Corrected calcium in mmol/L (mg/dL × 0.2495). Unit: mmol/L.","type":"number","x-unit":"mmol/L"},"interpretation":{"description":"Against a typical adult range of 8.5–10.5 mg/dL (2.12–2.62 mmol/L); laboratory ranges vary.","type":"string"}}},"formula":"Conventional: corrected_Ca (mg/dL) = calcium + 0.8 × (4.0 − albumin_g_dl). SI: corrected_Ca (mmol/L) = calcium + 0.02 × (40 − albumin_g_l). 1 mmol/L = 4.008 mg/dL.","method":"Payne (1973) assumes 0.8 mg/dL of calcium is bound per 1 g/dL of albumin; the correction performs poorly in chronic kidney disease and critical illness, where ionised calcium should be measured. Results are informational only and not a substitute for clinical judgement or medical advice.","sources":[{"name":"Payne RB, Little AJ, Williams RB, Milner JR (1973) Interpretation of serum calcium in patients with abnormal serum proteins, Br Med J 4:643-646","url":"https://pubmed.ncbi.nlm.nih.gov/4758544/","type":"peer_reviewed","retrieved_at":"2026-09-24"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"Calcium 8.0 mg/dL, albumin 2.5 g/dL","inputs":{"calcium":8,"albumin":2.5,"unit_system":"conventional"},"expected":{"corrected_calcium":9.2,"corrected_calcium_mmol_l":2.3,"interpretation":"Within the typical range (8.5–10.5 mg/dL)"},"url":"https://tttkmbb.com/api/v1/calculate/corrected-calcium?calcium=8&albumin=2.5&unit_system=conventional"},{"name":"Calcium 2.10 mmol/L, albumin 30 g/L","inputs":{"calcium":2.1,"albumin":30,"unit_system":"si"},"expected":{"corrected_calcium":2.3,"corrected_calcium_mg_dl":9.22},"url":"https://tttkmbb.com/api/v1/calculate/corrected-calcium?calcium=2.1&albumin=30&unit_system=si"}],"faq":[{"q":"My lab reports albumin in g/L; which system do I use?","a":"Choose si and enter calcium in mmol/L and albumin in g/L (a g/dL value × 10)."},{"q":"When is the correction unreliable?","a":"In renal failure, after surgery, with abnormal pH, paraproteins or very low albumin the formula misclassifies many patients; ionised calcium is the reference."}],"tags":["corrected calcium","albumin corrected calcium","hypocalcemia","hypercalcemia","payne formula"],"related":[{"calculator_id":"anion-gap","reason":"Albumin also changes the expected anion gap."},{"calculator_id":"egfr","reason":"Kidney function affects calcium interpretation."}],"links":{"html":"https://tttkmbb.com/medical/corrected-calcium","markdown":"https://tttkmbb.com/medical/corrected-calcium.md","json":"https://tttkmbb.com/medical/corrected-calcium.json","api":"https://tttkmbb.com/api/v1/calculate/corrected-calcium","schema":"https://tttkmbb.com/api/v1/calculators/corrected-calcium","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T01:48:39Z"}