HbA1c: the three-month blood sugar average

Schöttker et al. 2016 linked HbA1c of 6.0 to just under 6.5 with a higher risk of dying, from any cause, than 5.0 to just under 5.5 in adults 50 and older without diabetes.

Read your number

Is my HbA1c good?

Read your lab result with your clinician, including whether you have diabetes and what treatment you use. Schöttker 2016 linked HbA1c of 6.0 to below 6.5% with higher death rates than 5.0 to below 5.5% in adults 50 and older without diabetes. The score’s curve is a model, rather than a treatment target. ACCORD 2008 studied intensive glucose lowering in high-risk adults with type 2 diabetes: a different population and a different question.

If you're 70 or older

At 70 and older, use your result to start a conversation about a goal that fits your health and treatment. The older-adult comparison on this page comes from people without diabetes; if you have diabetes, use diabetes-specific clinical guidance. Practical food and activity options below include whole-food carbohydrates and protein with meals, and walking after meals.

Try your numbers in the free calculator Choose a practical next step

Evidence already on this page: Schöttker et al. 2016; ACCORD Study Group (Gerstein et al.) 2008.

Where you stand

Going below the normal range earns no extra credit in the score. And lower is not always better: in people with diabetes, pushing it under 6% with intensive treatment raised deaths in the ACCORD trial.

Flat up to 5.6%, then climbing. Past 8% the curve is the model’s estimate, not a study result.

At 5.9%1.10×a typical 45-year-old’s risk, a little higher than typical.

See the same numbers as a table

HbA1c and risk of death from any cause, as a multiple of a typical 45-year-old’s risk
HbA1c, %	Risk vs typical	In words
4.0%	1.00×	about the same as typical
5.0%	1.00×	about the same as typical
5.6%	1.00×	about the same as typical
6.0%	1.15×	a little higher than typical
7.0%	1.55×	much higher than typical
8.0%	1.95×	much higher than typical
10.0%	over 2.6×	much higher than typical; beyond the studies, so this is the model’s estimate

Risk of death from any cause, with every other marker held at typical. Drag the marker or use the arrow keys. Nothing you move here is saved.

Hatched areas are beyond the studies. The line there is the model’s estimate, or flat.

The line runs off the top of the chart just before 10%. No published curve reaches that high.

Source: Schöttker et al. 2016, BMC Medicine (PMID 26867584)

The study, not the score

HbA1c 6.0–<6.5% vs 5.0–<5.5% (non-diabetic, age 50+)

Schöttker et al. 2016 · a different study from the one the score uses

1.14 (1.03–1.27)

14% higher all-cause mortality

The bar shows the study’s 95% confidence interval, the range of values consistent with its data. The tick is the study’s best single figure. The centre line is no difference. The chart above is the score’s own curve, not this study.

What it is

A three-month average of blood glucose, as a percentage. It is the standard test for diabetes and prediabetes. The 6.0–6.4 band is the one most people are told is only borderline.

How the score uses it

Technical notes

The curve is a constructed smooth curve (flat 1.00 from 4.0–5.6%; then 6.0=1.15, 6.5=1.35, 7.0=1.55, 8.0=1.95, 10.0=2.7). Zhong’s 2016 meta-analysis is about 10 years old. The old 0.88 low-end reward was removed and no uptick was added. The overlay is Zhong 2016: without-known-diabetes dose-response, 12 studies, 113,526 people / 11,301 deaths, HR 1.03 (1.01–1.04) per 1%, I² 28.9%, “relatively flat … less than around 5.7%.” After excluding undiagnosed diabetes (HbA1c ≥6.5%) all-cause mortality is 1.01 (0.99–1.03); after also excluding prediabetes, 1.01 (0.98–1.03), NS. Authors: driven by undiagnosed diabetes or prediabetes. Curve 1.15 at 6.0% is not Zhong’s 1.03/1%. Supporting: Schöttker 2016 individual-participant data (non-diabetic ≥50, 28,681 / 6,769 deaths; 6.0–<6.5% vs 5.0–<5.5% all-cause mortality 1.14 (1.03–1.27); no J after confounders) / Cavero-Redondo 2017 (categorical U — non-diabetic >6.0% 1.74, <5.0% 1.19; not this curve) / ACCORD 2008 (intensive target <6% all-cause mortality HR 1.22 (1.01–1.46) — marker, not a treatment goal).

How to improve it

Choose whole-food carbs and protein with meals
Walk after meals to blunt glucose spikes
Build muscle to improve insulin sensitivity

What the studies found

Endpoint	Grade	Finding
—	METHOD	smooth curve is constructed (flat 1.00 to 5.6%) Technical notes Anchor points 4.0–5.6 = 1.00, then 6.0=1.15, 6.5=1.35, 7.0=1.55, 8.0=1.95, 10.0=2.7. The old 0.88 reward was flattened; no low-end uptick was added.
All-cause mortality	B	Zhong is 1.03/1% and loses all-cause mortality after exclusions Technical notes Zhong 2016: without-known-diabetes dose-response HR 1.03 (1.01–1.04) per 1%, flat below ~5.7%. After excluding undiagnosed diabetes: all-cause mortality 1.01 (0.99–1.03). Not this calculator’s 1.15 at 6.0%.
All-cause mortality	C	1.74 / 1.19 is not this score (Cavero 2017) Technical notes Non-diabetic categorical >6.0% HR 1.74; <5.0% 1.19. Curve is 1.15 at 6.0% and 1.00 below 5.6%. ACCORD intensive <6% raised all-cause mortality (HR 1.22) — marker, not a treatment target.
All-cause mortality	C	1.14 for “Increased” vs Low, After CV Adjustment (Schöttker 2016) Technical notes Individual-participant pooling of 6 European/US cohorts (28,681 non-diabetic adults 50+, 6,769 deaths, mean 10.7 years): an “increased” HbA1c of 6.0–<6.5% carried all-cause mortality HR 1.14 (1.03–1.27) versus a “low” 5.0–<5.5% band after cardiovascular-risk adjustment, which explained about half the excess. The very-low (<5.0%) band was not significant. The authors said their data “do not support the notion of a J-shaped association.”
All-cause mortality	A	Intensive Control Raised Death in T2D (Gerstein 2008) Technical notes ACCORD randomized high-risk type 2 diabetics to an intensive HbA1c target under 6.0% (median achieved 6.4%) versus standard 7.0–7.9% (median 7.5%). The intensive arm did not reduce the primary MACE outcome (HR 0.90, 0.78–1.04, not significant) and had significantly higher all-cause mortality — 257 vs 203 deaths, HR 1.22 (1.01–1.46), P=0.04. A target this calculator scores as 1.00–1.15 raised death in that trial.
All-cause mortality	C	Low HbA1c Also Carries Risk, HR 1.32 (Aggarwal 2012) Technical notes ARIC cohort of 13,288 adults: HbA1c under 5.0% versus 5.0–<5.7% carried all-cause mortality HR 1.32 (1.13–1.55) and cancer-death HR 1.47 (1.16–1.84). The authors called low HbA1c a “generalized marker of mortality risk,” likely mixing healthy people with people whose low HbA1c signals underlying illness — this calculator does not implement a low-end penalty.
All-cause mortality	B	+28% all-cause mortality Per 1% Higher HbA1c (Khaw 2001) Technical notes EPIC-Norfolk cohort of 4,662 men aged 45–79: each 1% higher HbA1c carried 28% higher all-cause mortality (P<0.002). After excluding known diabetes, HbA1c ≥7%, and prior MI or stroke, the relative risk was 1.46 (P=0.05) — and 82% of the excess population mortality occurred in the 5.0–6.9% HbA1c range, well within what most people consider normal.
All-cause mortality	C	Prediabetes Definition Changes the Answer (Cai 2020) Technical notes Updated meta-analysis of 129 studies (10.07 million people): general-population prediabetes carried all-cause mortality RR 1.13 (1.10–1.17) overall, but broken out by definition, all-cause mortality was raised for the HbA1c-IEC band of 6.0–6.4% (RR 1.21, 1.06–1.38) and for IFG/IGT — not for the broader HbA1c-ADA band of 5.7–6.4%.

What argues against this

Cavero-Redondo et al. 2017 (meta-analysis of 46-74 studies, non-diabetic populations) is the strongest opposing source: it found all-cause mortality HR 1.74 (1.38–2.20) above 6.0% — well above the curve's 1.15 anchor point at that point — and also found the <5.0% band carrying HR 1.19 (1.04–1.36), suggesting a U-shaped low end the curve's flat-to-5.6% curve does not implement. This disagrees with the curve mainly on magnitude and shape (steeper top end, a low-end uptick), not on the basic sign of the association.

Last reviewed 12 October 2026

Sources

8 cited

Zhong et al. (2016) — Scientific Reports
HbA1c and Risks of All-Cause and Cause-Specific Death in Subjects without Known Diabetes: A Dose-Response Meta-Analysis of Prospective Cohort Studies
View source
Schöttker et al. (2016) — BMC Medicine
HbA1c levels in non-diabetic older adults - No J-shaped associations with primary cardiovascular events, cardiovascular and all-cause mortality after adjustment for confounders in a meta-analysis of individual participant data from six cohort studies
View source
Cavero-Redondo et al. (2017) — BMJ Open
Glycated haemoglobin A1c as a risk factor of cardiovascular outcomes and all-cause mortality in diabetic and non-diabetic populations: a systematic review and meta-analysis
View source
ACCORD Study Group (Gerstein et al.) (2008) — New England Journal of Medicine
Effects of Intensive Glucose Lowering in Type 2 Diabetes
View source
Aggarwal et al. (2012) — Diabetes Care
Low hemoglobin A1c in nondiabetic adults: an elevated risk state?
View source
Khaw et al. (2001) — BMJ
Glycated haemoglobin, diabetes, and mortality in men in Norfolk cohort of european prospective investigation of cancer and nutrition (EPIC-Norfolk)
View source
Cai et al. (2020) — BMJ
Association between prediabetes and risk of all cause mortality and cardiovascular disease: updated meta-analysis
View source
Huang et al. (2025) — Frontiers in Endocrinology
Nonlinear association between glycated hemoglobin levels and mortality in elderly patients with non-diabetic chronic kidney disease: a national health and nutrition examination survey analysis
View source

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