In an adult with HbA1c 6.2% and normal renal function (estimated glomerular filtration rate ≥60 mL/min) and no contraindications, should metformin or any other antidiabetic medication be started?

HbA1c 6.2%: Do Not Start Metformin or Other Diabetic Medications

An HbA1c of 6.2% falls within the prediabetes range (5.7–6.4%), not diabetes, and pharmacologic therapy is not indicated at this level. 1

Diagnostic Classification

• HbA1c 6.2% meets criteria for prediabetes, not diabetes (which requires HbA1c ≥6.5%). 1
• Approximately two-thirds of people with prediabetes never progress to diabetes, even after many years of follow-up. 2
• Roughly one-third of individuals with prediabetes return to normal glucose regulation without pharmacologic intervention. 2

Why Metformin Should Not Be Started

• Metformin is not indicated for prediabetes because individuals at this glycemic level are not at risk for microvascular complications of diabetes (retinopathy, nephropathy, neuropathy), which are the primary targets of glucose-lowering therapy. 2
• The association between prediabetes and cardiovascular disease stems from non-glycemic risk factors (hypertension, dyslipidemia, obesity) rather than the slightly elevated glucose itself, so lowering HbA1c from 6.2% provides no immediate cardiovascular benefit. 2
• Starting a lifelong medication when the patient may never develop diabetes—and when one-third will spontaneously revert to normal—exposes them to unnecessary medication burden, cost, and potential adverse effects (gastrointestinal intolerance, vitamin B12 deficiency). 2, 3

Recommended Management Strategy

Lifestyle Modification (First-Line)

• Prescribe a 7–10% reduction in body weight through caloric restriction if the patient is overweight or obese. 1
• Recommend ≥150 minutes per week of moderate-intensity aerobic activity (e.g., brisk walking) plus resistance training 2–3 times weekly. 4
• Advise focusing on nutrient-dense, high-quality foods while decreasing calorie-dense, nutrient-poor items, particularly sugar-added beverages. 1

Monitoring Protocol

• Recheck HbA1c in 3 months to assess response to lifestyle changes. 1
• If HbA1c remains 6.0–6.4% or rises to ≥6.5%, reassess for diabetes diagnosis and consider pharmacologic therapy at that time. 2
• Screen and manage other cardiovascular risk factors (blood pressure, LDL cholesterol, smoking), which are more important than glucose level at this stage. 1

When to Consider Metformin in Prediabetes (Narrow Exception)

• Metformin may be considered only in the highest-risk subgroup: those with HbA1c 6.0–6.4% (not 6.2% alone), fasting glucose 110–125 mg/dL, and a history of gestational diabetes. 2
• Even in this group, the recommendation is to follow closely and introduce metformin only when diabetes is diagnosed (HbA1c ≥6.5%), not preemptively. 2

Critical Pitfalls to Avoid

• Do not start metformin at HbA1c 6.2% simply because it is "elevated"; this medicalizes a condition that may resolve spontaneously and exposes the patient to unnecessary treatment. 2
• Do not delay lifestyle intervention while waiting to see if HbA1c rises; weight loss and exercise are effective now and carry no adverse effects. 1
• Do not ignore cardiovascular risk factors; at HbA1c 6.2%, optimizing blood pressure, lipids, and smoking cessation will provide greater benefit than glucose lowering. 1