HbA1c 4.1% · 21 mmol/mol

HbA1c 4.1%

Converted with the published ADAG regression. What it means for you is a question for a doctor, not for this page.

Converted value

71mg/dL eAG

An HbA1c of 4.1% converts to an estimated average glucose of about 71 mg/dL — 3.9 mmol/L. In IFCC units the same result is 21 mmol/mol.

Against the American Diabetes Association criteria, 4.1% is below the prediabetes range. That describes where the value sits on a published scale. It is not a diagnosis, and a diagnosis requires confirmation and a doctor.

Central estimate, not a reading. The regression explained about 84% of the variation, so real averages sit either side of this figure.

SOURCE·ADAG regression, Diabetes Care 2008 · NGSP master equation·bands from ADA Standards of Care 2025·REVIEWED JUL 2026

This page is reference information, not medical advice.

Nothing here can diagnose you, and nothing here is a treatment plan. Blood glucose results are interpreted by a doctor alongside your history, your symptoms and a repeat test — a single number on a screen is not a diagnosis. If any reading concerns you, or if you feel unwell, see a doctor rather than a website.

The arithmetic behind 4.1%

The ADAG regression is applied directly: 28.7 × 4.1 − 46.7 = 71.0 mg/dL.
That figure is divided by 18.016, the molar mass of glucose in these units, giving 3.94 mmol/L.
The NGSP master equation converts the percentage to the IFCC unit: (4.1 − 2.15) × 10.929 = 21.3 mmol/mol.
Rounded for display to 71 mg/dL, 3.9 mmol/L and 21 mmol/mol — the precision laboratories report.
Nothing on this page is interpreted. Where the value sits against a published band is a fact about the band; what it means for a person is a clinical judgement.

28.7 x 4.1 - 46.7        = 71.0 mg/dL
71.0 / 18.016             = 3.94 mmol/L
(4.1 - 2.15) x 10.929   = 21.3 mmol/mol

Full methodology →

Provenance

The equations, and who published them

The regression is the ADAG equation from Diabetes Care 2008, which is the one the American Diabetes Association uses; the mmol/mol line is the NGSP master equation. Neither was adjusted here.

Source: Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ, for the A1c-Derived Average Glucose (ADAG) Study Group. Translating the A1C assay into estimated average glucose values. Diabetes Care 2008;31(8):1473–1478. Link
Source: National Glycohemoglobin Standardization Program (NGSP) — HbA1c and estimated average glucose (eAG). Link

Neighbouring rows

Where 4.1% sits

HbA1c converted to estimated average glucose with the ADAG regression, eAG (mg/dL) = 28.7 × A1C − 46.7. The mmol/mol column is the IFCC unit, from the NGSP master equation. The final column reads the A1C against the ADA diagnostic bands.
HbA1c (%)	mmol/mol	eAG (mg/dL)	eAG (mmol/L)	Where it sits
4.0%	20	68	3.8	Below the prediabetes range
4.1%	21	71	3.9	Below the prediabetes range
4.2%	22	74	4.1	Below the prediabetes range
4.3%	23	77	4.3	Below the prediabetes range
4.4%	25	80	4.4	Below the prediabetes range
4.5%	26	82	4.6	Below the prediabetes range
4.6%	27	85	4.7	Below the prediabetes range

Estimated average glucose is an average across roughly the previous three months. It is not a prediction of your reading tomorrow morning, and two people with the same HbA1c can have very different day-to-day swings.

SOURCE·ADAG regression (Diabetes Care 2008) · NGSP master equation·REVIEWED JUL 2026

The complete chart from 4.0% to 14.0% →

What this page is careful not to say

It does not tell you whether 4.1% is good or bad for you, because that depends on things a web page cannot see — whether you have already been diagnosed, what else is on your report, whether you have a condition that makes HbA1c unreliable, and what your doctor is trying to achieve. It publishes no targets for anyone.

A result below the prediabetes range is reassuring at the moment it was taken. It is not a permanent result, and it does not mean testing never needs repeating.

PeakForm is a training and accountability programme. It is not a treatment for diabetes or prediabetes, it is not a substitute for your doctor's advice, and nothing on this site should be acted on before speaking to one.

Nearby values

4.0%68 mg/dL 4.1%71 mg/dL 4.2%74 mg/dL 4.3%77 mg/dL 4.4%80 mg/dL 4.5%82 mg/dL 4.6%85 mg/dL

Questions this report anticipates

What does an HbA1c of 4.1% mean?

On the American Diabetes Association criteria, 4.1% is below the prediabetes range. It converts to an estimated average glucose of about 71 mg/dL (3.9 mmol/L) using the ADAG equation. A single value is not a diagnosis — published criteria require confirmation, and interpretation belongs to a doctor.

What is 4.1% HbA1c in mg/dL?

About 71 mg/dL as an estimated average glucose across the previous two to three months, from eAG = 28.7 × 4.1 − 46.7. That is an average, not a reading you would expect to see on a meter at any particular moment.

What is 4.1% in mmol/mol?

21 mmol/mol, using the NGSP master equation (percentage − 2.15) × 10.929. Both units describe the same measurement.

General information only — NOT medical advice, and never a diagnosis. Only a doctor can interpret your results and diagnose or treat diabetes. If a reading concerns you, see a doctor rather than a website. Every threshold, equation and glycemic index value used on this site is listed with its publication on the data & method page, and every publication is listed with its issuing body and its date in the source register.

SOURCE·Published reference ranges + GI tables·REVIEWED JUL 2026

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