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HbA1c: your three-month blood sugar average and longevity

Each row is one study of death risk from hba1c. The bright line is what that study found. The band around it is the range the data still supports — it fades where the evidence thins. Left of the centre line is lower risk.

what the study foundstill plausibleno change
HbA1c 6.0–<6.5% vs 5.0–<5.5% (non-diabetic, age 50+)
Schöttker et al. 2016
14% higher
range 3–27% higher
intensive target below 6.0% vs standard 7.0–7.9% (high-risk type 2 diabetes, RCT)
ACCORD Study Group (Gerstein et al.) 2008
22% higher
range 1–46% higher
HbA1c below 5.0% vs 5.0–<5.7% (the low end)
Aggarwal et al. 2012
32% higher
range 13–55% higher

What it is

HbA1c reflects average blood glucose over roughly three months. It’s the standard test for diabetes and prediabetes.

Why it matters for longevity

The engine is a constructed PCHIP (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). Council 2026-08-29 3–0 removed the old 0.88 low-end reward; 2–1 against adding an uptick. 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%) ACM 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. Engine 1.15 at 6.0% is not Zhong’s 1.03/1%. Under: Schöttker 2016 IPD (non-diabetic ≥50, 28,681 / 6,769 deaths; 6.0–<6.5% vs 5.0–<5.5% ACM 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% ACM HR 1.22 (1.01–1.46) — marker, not a treatment goal). Engine not moved.

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

Evidence, by endpoint

EndpointGradeFinding
—METHOD
PCHIP is constructed (flat 1.00 to 5.6%)
Knots 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. Council 3–0 flattened the old 0.88 reward; 2–1 against a low-end uptick. Engine not moved.
All-cause mortalityB
Zhong is 1.03/1% and loses ACM after exclusions
Without-known-diabetes dose-response HR 1.03 (1.01–1.04) per 1%, flat below ~5.7%. After excluding undiagnosed diabetes: ACM 1.01 (0.99–1.03). Not this calculator’s 1.15 at 6.0%.
All-cause mortalityC
1.74 / 1.19 is not this score (Cavero 2017)
Non-diabetic categorical >6.0% HR 1.74; <5.0% 1.19. Engine is 1.15 at 6.0% and 1.00 below 5.6%. ACCORD intensive <6% raised ACM (HR 1.22) — marker, not a treatment target.
All-cause mortalityC
1.14 for “Increased” vs Low, After CV Adjustment (Schöttker 2016)
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 ACM 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 mortalityA
Intensive Control Raised Death in T2D (Gerstein 2008)
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 mortalityC
Low HbA1c Also Carries Risk, HR 1.32 (Aggarwal 2012)
ARIC cohort of 13,288 adults: HbA1c under 5.0% versus 5.0–<5.7% carried ACM 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 mortalityB
+28% ACM Per 1% Higher HbA1c (Khaw 2001)
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 mortalityC
Prediabetes Definition Changes the Answer (Cai 2020)
Umbrella meta of 129 studies (10.07 million people): general-population prediabetes carried ACM RR 1.13 (1.10–1.17) overall, but broken out by definition, ACM 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 ACM HR 1.74 (1.38–2.20) above 6.0% — well above the engine's 1.15 knot 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 engine's flat-to-5.6% curve does not implement. This disagrees with the engine mainly on magnitude and shape (steeper top end, a low-end uptick), not on the basic sign of the association.

Last reviewed 2 September 2026

Evidence

  1. 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
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  2. 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
  3. 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
  4. ACCORD Study Group (Gerstein et al.) (2008) — New England Journal of Medicine
    Effects of Intensive Glucose Lowering in Type 2 Diabetes
    View source
  5. Aggarwal et al. (2012) — Diabetes Care
    Low hemoglobin A1c in nondiabetic adults: an elevated risk state?
    View source
  6. 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
  7. Cai et al. (2020) — BMJ
    Association between prediabetes and risk of all cause mortality and cardiovascular disease: updated meta-analysis
    View source
  8. 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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