Glucose control sits at the centre of diabetes care, yet its relationship to the diabetic foot is more nuanced than it first appears. Clinicians routinely tell patients that “tight sugars help wounds heal,” but the published evidence separates two distinct questions: whether hyperglycaemia predicts whether a limb is lost, and whether lowering glucose accelerates the closure of an ulcer already present. The literature of the past decade answers these questions differently, and understanding that distinction matters for how metabolic targets are framed in foot care.
Hyperglycaemia as a Risk Factor for Ulceration and Amputation
The case for glycaemic control as a determinant of long-term foot risk is strong. A systematic review of risk factors for diabetic foot complications in type 2 diabetes by Rossboth and colleagues screened 9,476 articles and identified poor glycaemic control and smoking as the only two consistently positive, modifiable risk factors across the included cohorts (Rossboth et al., Endocrinology, Diabetes & Metabolism, 2020). Peripheral neuropathy, retinopathy, nephropathy, insulin use and diabetes duration were also consistently associated with foot disease, but these are largely markers of accumulated exposure rather than levers that can be pulled directly.
That accumulated exposure is substantial. Hicks and Selvin estimated that diabetic peripheral neuropathy affects close to half of adults with diabetes over a lifetime, with prevalence varying by age, diabetes duration and degree of glucose control, and with roughly a 25% lifetime risk of foot ulceration in that population (Hicks & Selvin, Current Diabetes Reports, 2019). Hyperglycaemia is therefore best understood as an upstream driver: it contributes to the neuropathy and vascular disease that make ulceration possible, over years rather than weeks.
The A1C Threshold Signal
The most quantitatively useful synthesis comes from Lane and colleagues, who pooled 47 observational studies covering 12,604 diabetic foot ulcers. Compared with A1C below 8%, an A1C of 8% or higher was associated with a pooled odds ratio of 4.80 (95% CI 2.83–8.13) for lower extremity amputation. A fasting glucose of 126 mg/dL or above carried a pooled odds ratio of 1.46 (95% CI 1.02–2.09). Notably, comparisons at the lower threshold of 7.0–7.5% did not reach statistical significance (Lane et al., Journal of Diabetes and Its Complications, 2020). The authors also flagged a high risk of bias for cohort comparability, since many contributing studies did not adjust for confounders such as perfusion, infection severity or renal disease.
Why Glucose Control Does Not Reliably Predict Wound Closure
The same meta-analysis found no association between A1C category and wound healing, whether expressed as an odds ratio or a hazard ratio. This is consistent with a prospective clinic-based cohort of 270 patients and 584 wounds, in which baseline A1C was not associated with healing in either univariate or fully adjusted models, and prospective change in A1C showed no clinically meaningful relationship to long-term healing (Fesseha et al., Diabetes Care, 2018).
Interventional evidence is essentially absent. A Cochrane review sought randomised trials comparing intensive with conventional glycaemic control in people with active foot ulcers and identified only a single eligible trial, which reported no results. The reviewers concluded that it is not possible to say whether intensive glucose control helps or harms ulcer healing, while noting that intensive control has been linked to reduced amputation risk in type 2 diabetes more broadly (Fernando et al., Cochrane Database of Systematic Reviews, 2016). Once an ulcer exists, its trajectory appears to be dominated by offloading, perfusion, infection control and wound bed preparation rather than by glucose alone.
Beyond A1C: Variability and Drug-Specific Effects
Attention has shifted toward metrics that A1C cannot capture. Analyses of continuous glucose monitoring data have linked lower time in range, higher mean glucose, greater time above range and higher glycaemic risk index to diabetic foot risk in type 2 diabetes, suggesting that variability and exposure patterns carry information beyond a single averaged value — though the available data remain largely cross-sectional (Byeon, World Journal of Diabetes, 2025).
Agent selection has also come under scrutiny. A meta-analysis of randomised trials of SGLT2 inhibitors found a modest increase in amputation and peripheral arterial disease events with canagliflozin specifically (amputation OR 1.60, 95% CI 1.04–2.46; PAD OR 1.53, 95% CI 1.14–2.05), with no consistent signal for the class as a whole (Lin et al., Cardiovascular Diabetology, 2021). A subsequent collaborative meta-analysis of 13 trials involving 90,413 participants concluded that the absolute cardiovascular and renal benefits of SGLT2 inhibition outweighed the serious hazards of ketoacidosis or amputation (Nuffield Department of Population Health SGLT2 Inhibitor Meta-Analysis Cataloguing Analyses, The Lancet, 2022).
Clinical Summary
Sustained hyperglycaemia, particularly A1C at or above 8%, is associated with a markedly higher likelihood of lower extremity amputation among people with diabetic foot ulcers, and poor glucose control remains one of the few consistently modifiable risk factors for developing foot disease in the first place. Evidence that lowering glucose speeds the healing of an established ulcer, however, is absent rather than negative — no adequately powered randomised trial has answered the question. Glycaemic management is best positioned as a limb-preservation and prevention strategy operating over months and years, complementing rather than substituting for offloading, revascularisation, infection management and wound care in the treatment of an active ulcer.
References
- Lane KL, Abusamaan MS, Voss BF, et al. Glycemic control and diabetic foot ulcer outcomes: A systematic review and meta-analysis of observational studies. Journal of Diabetes and Its Complications. 2020;34(10):107638.
- Fesseha BK, Abularrage CJ, Hines KF, et al. Association of hemoglobin A1c and wound healing in diabetic foot ulcers. Diabetes Care. 2018;41(7):1478–1485.
- Fernando ME, Seneviratne RM, Tan YM, et al. Intensive versus conventional glycaemic control for treating diabetic foot ulcers. Cochrane Database of Systematic Reviews. 2016;(1):CD010764.
- Rossboth S, Lechleitner M, Oberaigner W. Risk factors for diabetic foot complications in type 2 diabetes — a systematic review. Endocrinology, Diabetes & Metabolism. 2020;4(1):e00175.
- Hicks CW, Selvin E. Epidemiology of peripheral neuropathy and lower extremity disease in diabetes. Current Diabetes Reports. 2019;19(10):86.
- Lin C, Zhu X, Cai X, et al. SGLT2 inhibitors and lower limb complications: an updated meta-analysis. Cardiovascular Diabetology. 2021;20(1):91.
- Nuffield Department of Population Health SGLT2 Inhibitor Meta-Analysis Cataloguing Analyses (SMART-C). Impact of diabetes on the effects of sodium glucose co-transporter-2 inhibitors on kidney outcomes: collaborative meta-analysis of large placebo-controlled trials. The Lancet. 2022;400(10365):1788–1801.
- Byeon H. Future of diabetic foot risk: Unveiling predictive continuous glucose monitoring biomarkers. World Journal of Diabetes. 2025;16(6):107006.
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