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A1C to Average Glucose Calculator

Q: Is eAG the same as my meter average?

Roughly, if the meter average covers all times of day over about 3 months; A1C weights the most recent 4–6 weeks more heavily, and meter checks often miss post-meal peaks.

Q: What is the mmol/mol value?

The IFCC unit used in the UK, Australia and much of Europe; 7% NGSP corresponds to 53 mmol/mol.

Converts HbA1c (%) to estimated average glucose in mg/dL and mmol/L with the ADAG study equation, or an average glucose back to A1C, and reports the IFCC value in mmol/mol.

When to use

You want the average glucose implied by an A1C result, the A1C implied by an average glucose from a meter or CGM, or the NGSP-to-IFCC conversion.

Do not use when: Conditions alter haemoglobin glycation (haemoglobinopathies, anaemia, recent transfusion, pregnancy, kidney failure), where A1C does not track average glucose.

Formula

eAG (mg/dL) = 28.7 × A1C − 46.7; eAG (mmol/L) = 1.59 × A1C − 2.59; inverse: A1C = (eAG_mg_dl + 46.7) / 28.7 or (eAG_mmol_l + 2.59) / 1.59; IFCC (mmol/mol) = (A1C − 2.15) × 10.929

The ADAG regression (Nathan 2008) has a 95% prediction interval of roughly ±30 mg/dL at an A1C of 7%, so individual eAG values are approximate. Results are informational only and not a substitute for clinical judgement or medical advice.

Inputs

Parameter	Type	Required	Description
`direction`	enum: a1c_to_glucose \| glucose_to_a1c	default a1c_to_glucose	Which quantity is being converted.
`value`	number	yes	A1C in percent (NGSP) for a1c_to_glucose, or average glucose (in glucose_unit) for glucose_to_a1c. Range: > 0, ≤ 1000
`glucose_unit`	enum: mg_dl \| mmol_l	default mg_dl	Unit of the glucose value (1 mmol/L = 18.016 mg/dL).

Outputs

Output	Type	Unit	Description
`a1c_percent`	number	%	Haemoglobin A1c in NGSP/DCCT percent.
`a1c_mmol_mol`	number	mmol/mol	IFCC units: (A1C% − 2.15) × 10.929.
`eag_mg_dl`	number	mg/dL	28.7 × A1C − 46.7.
`eag_mmol_l`	number	mmol/L	1.59 × A1C − 2.59.
`a1c_category`	string		Diagnostic ranges: <5.7% normal, 5.7–6.4% prediabetes, ≥6.5% diabetes (requires confirmation).

Example

A1C 7%: {"direction":"a1c_to_glucose","value":7} → {"a1c_percent":7,"eag_mg_dl":154,"eag_mmol_l":8.5,"a1c_mmol_mol":53,"a1c_category":"Diabetes range (≥6.5%)"}

Average glucose 126 mg/dL: {"direction":"glucose_to_a1c","value":126,"glucose_unit":"mg_dl"} → {"a1c_percent":6,"a1c_mmol_mol":42,"a1c_category":"Prediabetes range (5.7–6.4%)"}

GET https://tttkmbb.com/api/v1/calculate/a1c-to-glucose?direction=a1c_to_glucose&value=7

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/a1c-to-glucose (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/a1c-to-glucose · Markdown: https://tttkmbb.com/medical/a1c-to-glucose.md · JSON definition: https://tttkmbb.com/medical/a1c-to-glucose.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="a1c-to-glucose"
OpenAPI operationId: convert_a1c_to_glucose
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Is eAG the same as my meter average?

Roughly, if the meter average covers all times of day over about 3 months; A1C weights the most recent 4–6 weeks more heavily, and meter checks often miss post-meal peaks.

What is the mmol/mol value?

The IFCC unit used in the UK, Australia and much of Europe; 7% NGSP corresponds to 53 mmol/mol.

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