{
  "id": "gmi",
  "version": "16d1c4c7bdf9",
  "status": "published",
  "name": "GMI Calculator",
  "question": "What is my GMI?",
  "summary": "Works out the glucose management indicator (GMI), the A1C level usually seen with a given mean glucose from continuous glucose monitoring (CGM), in percent and mmol/mol, with the Bergenstal 2018 formulas.",
  "category": "health",
  "subcategory": "clinical",
  "url": "https://www.acalculator.org/health/gmi-calculator",
  "markdown": "https://www.acalculator.org/health/gmi-calculator.md",
  "kind": "function",
  "method": "GMI (%) = 3.31 + 0.02392 × mean glucose (mg/dL); GMI (mmol/mol) = 12.71 + 4.70587 × mean glucose (mmol/L); 1 mmol/L = 18 mg/dL. Each GMI is rounded once to 1 decimal, halves up.",
  "assumptions": [
    "The mean glucose comes from at least 10, and preferably 14 or more, days of CGM readings (Bergenstal 2018).",
    "The formulas come from 528 people with type 1 or type 2 diabetes who wore Dexcom sensors; a lab A1C can differ from the GMI.",
    "Each result is worked from the exact typed value and rounded once to 1 decimal, halves up."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "units": {
        "title": "Glucose unit",
        "description": "The unit of the mean glucose on the CGM report: mg/dL or mmol/L.",
        "type": "string",
        "enum": [
          "mgdl",
          "mmol"
        ]
      },
      "mgdl": {
        "title": "Mean glucose (mg/dL)",
        "description": "The mean glucose from 14 or more days of CGM readings, 90 to 350 mg/dL.",
        "type": "number",
        "minimum": 90,
        "maximum": 350
      },
      "mmol": {
        "title": "Mean glucose (mmol/L)",
        "description": "The mean glucose from 14 or more days of CGM readings, 5 to 19.4 mmol/L.",
        "type": "number",
        "minimum": 5,
        "maximum": 19.4
      }
    }
  },
  "outputs": {
    "gmi": {
      "label": "GMI (%)",
      "description": "GMI = 3.31 + 0.02392 × mean glucose in mg/dL, to 1 decimal.",
      "format": "percent"
    },
    "ifcc": {
      "label": "GMI (mmol/mol)",
      "description": "GMI = 12.71 + 4.70587 × mean glucose in mmol/L, to 1 decimal.",
      "format": "number"
    },
    "glucoseMmol": {
      "label": "Mean glucose (mmol/L)",
      "description": "The typed mg/dL ÷ 18, to 1 decimal.",
      "format": "number"
    },
    "glucoseMgdl": {
      "label": "Mean glucose (mg/dL)",
      "description": "The typed mmol/L × 18, to a whole number.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "units": "mgdl",
      "mgdl": 150,
      "mmol": 8
    },
    "outputs": {
      "gmi": 6.9,
      "ifcc": 51.9,
      "glucoseMmol": 8.3
    },
    "text": "The GMI is 6.9%, or 51.9 mmol/mol."
  },
  "examples": [
    {
      "given": {
        "units": "mgdl",
        "mgdl": 150
      },
      "expect": {
        "gmi": 6.9,
        "ifcc": 51.9,
        "glucoseMmol": 8.3
      },
      "source": "Bergenstal 2018, Table 1: 150 mg/dL gives a GMI of 6.9% (3.31 + 0.02392 × 150 = 6.898); 12.71 + 4.70587 × 150 ÷ 18 = 51.93 mmol/mol (hand calculation in content.mdx)"
    },
    {
      "given": {
        "units": "mgdl",
        "mgdl": 100
      },
      "expect": {
        "gmi": 5.7,
        "ifcc": 38.9,
        "glucoseMmol": 5.6
      },
      "source": "Bergenstal 2018, Table 1: 100 mg/dL gives 5.7% (3.31 + 2.392 = 5.702); 12.71 + 4.70587 × 100 ÷ 18 = 38.85 mmol/mol (hand calculation in content.mdx)"
    },
    {
      "given": {
        "units": "mgdl",
        "mgdl": 350
      },
      "expect": {
        "gmi": 11.7,
        "ifcc": 104.2,
        "glucoseMmol": 19.4
      },
      "source": "Bergenstal 2018, Table 1: 350 mg/dL gives 11.7% (3.31 + 8.372 = 11.682) (hand calculation in content.mdx)"
    },
    {
      "given": {
        "units": "mmol",
        "mmol": 5
      },
      "expect": {
        "ifcc": 36.2,
        "gmi": 5.5,
        "glucoseMgdl": 90
      },
      "source": "Bergenstal 2018, Table 1: 5 mmol/L gives 36.2 mmol/mol (12.71 + 23.52935 = 36.23935); 5 × 18 = 90 mg/dL gives 5.4628% (hand calculation in content.mdx)"
    },
    {
      "given": {
        "units": "mmol",
        "mmol": 10
      },
      "expect": {
        "ifcc": 59.8,
        "gmi": 7.6,
        "glucoseMgdl": 180
      },
      "source": "Bergenstal 2018, Table 1: 10 mmol/L gives 59.8 mmol/mol (12.71 + 47.0587 = 59.7687); 180 mg/dL gives 7.6156% (hand calculation in content.mdx)"
    },
    {
      "given": {
        "units": "mmol",
        "mmol": 18
      },
      "expect": {
        "ifcc": 97.4,
        "gmi": 11.1,
        "glucoseMgdl": 324
      },
      "source": "Bergenstal 2018, Table 1: 18 mmol/L gives 97.4 mmol/mol (12.71 + 84.70566 = 97.41566) (hand calculation in content.mdx)"
    },
    {
      "given": {
        "units": "mgdl",
        "mgdl": 112.5
      },
      "expect": {
        "gmi": 6,
        "ifcc": 42.1,
        "glucoseMmol": 6.3
      },
      "source": "3.31 + 0.02392 × 112.5 = 6.001; 12.71 + 4.70587 × 6.25 = 42.1216875 (hand calculation in content.mdx)"
    }
  ],
  "sources": [
    "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(11):2275-2280 (both formulas, Table 1, Table 3). https://doi.org/10.2337/dc18-1581 (full text: https://pmc.ncbi.nlm.nih.gov/articles/PMC6196826/, retrieved 2026-10-18)",
    "PubChem. Glucose, CID 5793: molecular weight 180.16 g/mol, so 1 mmol/L = 18.016 mg/dL, which the page rounds to 18. https://pubchem.ncbi.nlm.nih.gov/compound/5793 (retrieved 2026-10-18)"
  ],
  "related": [
    "a1c"
  ],
  "changelog": [
    {
      "date": "2026-10-19",
      "note": "Published after this site's editorial review against the cited sources (no clinician review); the page notices say so."
    }
  ]
}