{
  "id": "a1c",
  "version": "64ef9ef548a2",
  "status": "published",
  "name": "A1C Calculator",
  "question": "What does my A1C mean?",
  "summary": "Converts an A1C result to estimated average glucose (ADAG equation, mg/dL and mmol/L) and to IFCC mmol/mol, or back, and shows the CDC range: normal, prediabetes, or diabetes.",
  "category": "health",
  "subcategory": "clinical",
  "url": "https://www.acalculator.org/health/a1c-calculator",
  "markdown": "https://www.acalculator.org/health/a1c-calculator.md",
  "kind": "formulas",
  "method": "eAG (mg/dL) = 28.7 × A1C − 46.7 (ADAG); eAG (mmol/L) = eAG (mg/dL) ÷ 18.0156; A1C (IFCC, mmol/mol) = (A1C − 2.15) ÷ 0.0915.",
  "assumptions": [
    "A1C is in NGSP percent units, the unit US labs report.",
    "The eAG equation is the average relationship found in the ADAG study; one person’s average glucose can differ from it.",
    "Blood loss, transfusion, iron-deficiency anemia, kidney failure, liver disease, and some hemoglobin variants can make an A1C result wrong (NIDDK).",
    "The ranges are the CDC’s diagnostic ranges for adults. They are not treatment targets, and this is not medical advice."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "a1c": {
        "title": "A1C",
        "description": "Hemoglobin A1C in percent (NGSP units), as a US lab reports it.",
        "type": "number",
        "x-unit": "percent",
        "minimum": 3,
        "maximum": 20
      },
      "eag": {
        "title": "Average glucose (mg/dL)",
        "description": "Estimated average blood glucose over about 3 months, in milligrams per decilitre.",
        "type": "number",
        "minimum": 20,
        "maximum": 600
      },
      "mmol": {
        "title": "Average glucose (mmol/L)",
        "description": "Estimated average blood glucose over about 3 months, in millimoles per litre.",
        "type": "number",
        "minimum": 1,
        "maximum": 35
      },
      "ifcc": {
        "title": "A1C (mmol/mol)",
        "description": "Hemoglobin A1C in IFCC units, millimoles per mole, as labs outside the US report it.",
        "type": "number",
        "minimum": 5,
        "maximum": 220
      }
    }
  },
  "solve": {
    "fillAny": 1,
    "variables": [
      "a1c",
      "eag",
      "mmol",
      "ifcc"
    ],
    "inputsOnly": []
  },
  "outputs": {
    "a1c": {
      "label": "A1C",
      "description": "Hemoglobin A1C in percent (NGSP units), with its CDC range.",
      "format": "percent"
    },
    "eag": {
      "label": "Average glucose (mg/dL)",
      "description": "Estimated average glucose in mg/dL: 28.7 × A1C − 46.7 (ADAG study).",
      "format": "number"
    },
    "eagMmol": {
      "label": "Average glucose (mmol/L)",
      "description": "Estimated average glucose in mmol/L: the mg/dL value ÷ 18.0156.",
      "format": "number"
    },
    "ifcc": {
      "label": "A1C (mmol/mol)",
      "description": "A1C in IFCC units: (A1C − 2.15) ÷ 0.0915.",
      "format": "number"
    },
    "range": {
      "label": "Range",
      "description": "The CDC A1C range: normal below 5.7%, prediabetes 5.7% to 6.4%, diabetes 6.5% or above.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "a1c": 7
    },
    "outputs": {
      "eag": 154.2,
      "eagMmol": 8.559248651168987,
      "ifcc": 53.005464480874316,
      "range": "Diabetes"
    },
    "text": "An A1C of 7% means an estimated average glucose of 154 mg/dL (8.6 mmol/L)."
  },
  "examples": [
    {
      "given": {
        "a1c": 6
      },
      "expect": {
        "eag": 125.5,
        "mmol": 6.966184862008481,
        "ifcc": 42.07650273224044,
        "range": "Prediabetes"
      },
      "source": "Nathan and others (2008), ADAG study: eAG = 28.7 × A1C − 46.7, so 6% is 125.5 mg/dL; mmol/L and IFCC by hand in content.mdx; CDC: 5.7% to 6.4% is prediabetes"
    },
    {
      "given": {
        "a1c": 7
      },
      "expect": {
        "eag": 154.2,
        "mmol": 8.559248651168987,
        "range": "Diabetes"
      },
      "source": "Nathan and others (2008): 28.7 × 7 − 46.7 = 154.2 mg/dL; CDC: 6.5% or above is the diabetes range"
    },
    {
      "given": {
        "eag": 154
      },
      "expect": {
        "a1c": 6.993031358885017
      },
      "source": "hand calculation in content.mdx: A1C = (154 + 46.7) ÷ 28.7 = 6.99%, the ADAG equation solved for A1C"
    },
    {
      "given": {
        "a1c": 5.7
      },
      "expect": {
        "ifcc": 38.797814207650276,
        "eag": 116.89,
        "range": "Prediabetes"
      },
      "source": "Hoelzel and others (2004): NGSP = 0.0915 × IFCC + 2.15, so 5.7% is (5.7 − 2.15) ÷ 0.0915 = 38.8 mmol/mol; CDC: 5.7% starts the prediabetes range"
    },
    {
      "given": {
        "ifcc": 48
      },
      "expect": {
        "a1c": 6.542,
        "range": "Diabetes"
      },
      "source": "Hoelzel and others (2004): 0.0915 × 48 + 2.15 = 6.542%; CDC: 6.5% or above is the diabetes range"
    }
  ],
  "sources": [
    "Nathan DM, Kuenen J, Borg R, et al. (A1c-Derived Average Glucose Study Group). Translating the A1C assay into estimated average glucose values. Diabetes Care 2008;31:1473–1478. doi:10.2337/dc08-0545",
    "Hoelzel W, Weykamp C, Jeppsson JO, et al. IFCC reference system for measurement of hemoglobin A1c in human blood and the national standardization schemes in the United States, Japan, and Sweden: a method-comparison study. Clinical Chemistry 2004;50:166–174. doi:10.1373/clinchem.2003.024802",
    "Centers for Disease Control and Prevention, Diabetes Testing (last reviewed May 15, 2024). https://www.cdc.gov/diabetes/diabetes-testing/index.html",
    "National Institute of Diabetes and Digestive and Kidney Diseases, The A1C Test & Diabetes (last reviewed April 2018). https://www.niddk.nih.gov/health-information/diagnostic-tests/a1c-test",
    "Bergenstal RM, Beck RW, Close KL, et al. Glucose Management Indicator (GMI): a new term for estimating A1C from continuous glucose monitoring. Diabetes Care 2018;41:2275–2280. doi:10.2337/dc18-1581",
    "IUPAC Commission on Isotopic Abundances and Atomic Weights, Abridged standard atomic weights (2021): C 12.011, H 1.008, O 15.999. https://ciaaw.org/abridged-atomic-weights.htm"
  ],
  "related": [
    "bmi",
    "ideal-weight"
  ],
  "changelog": []
}