What does an A1C (Hemoglobin A1C) level of 5.9 indicate and how is it managed?

A1C 5.9: Prediabetes Requiring Active Intervention

An A1C of 5.9% indicates prediabetes with substantially increased diabetes risk, and you should immediately counsel this patient on intensive lifestyle modification including weight loss and physical activity, with annual A1C monitoring. 1, 2

Diagnostic Classification

• This A1C level falls within the prediabetes range (5.7-6.4%), which the American Diabetes Association defines as high-risk for progression to type 2 diabetes 1, 2
• Individuals with A1C between 5.5-6.0% have a 5-year diabetes incidence of 9-25%, representing a substantially increased risk compared to those with A1C <5.0% 1, 3
• This patient's A1C of 5.9% places them at the higher end of this risk spectrum, approaching the 6.0-6.5% range where 5-year diabetes risk jumps to 25-50% 1, 3
• The estimated average glucose for this A1C is approximately 123 mg/dL 4

Risk Stratification and Prognosis

• The relative risk of developing diabetes at this A1C level is approximately 20 times higher than someone with A1C of 5.0% 1
• This A1C level is associated with increased risk for both diabetes AND cardiovascular disease, not just diabetes alone 2
• Risk exists on a continuum—even within the "prediabetes" range, higher values confer progressively greater risk 2
• Additional risk factors that amplify diabetes risk include: obesity (BMI ≥25 kg/m²), first-degree relative with diabetes, high-risk ethnicity, history of cardiovascular disease, hypertension, low HDL cholesterol (<35 mg/dL), elevated triglycerides (>250 mg/dL), PCOS, and physical inactivity 1

Management Strategy

Immediate Interventions

• Counsel on intensive lifestyle modification focusing on weight loss and increased physical activity—these interventions are proven effective in the Diabetes Prevention Program for patients with A1C levels both below and above 5.9% 2
• Screen for and address cardiovascular disease risk factors including blood pressure, lipid panel, and smoking status 1
• Assess for additional diabetes risk factors listed above to refine risk stratification 1

Monitoring Protocol

• Perform annual A1C testing to track progression, as patients with prediabetes should be tested yearly 1, 2
• More frequent testing may be warranted if the patient has multiple additional risk factors or if initial lifestyle interventions are not successful 1

Common Pitfalls to Avoid

• Do not dismiss this A1C as "borderline" or "almost normal"—the risk is real and substantial, with 3-8 times higher diabetes incidence than the general U.S. population 2
• Do not wait until A1C reaches 6.5% to intervene—preventive interventions are most effective when initiated at the prediabetes stage 2
• Be aware that A1C may detect different proportions of at-risk individuals across ethnic groups, with higher sensitivity in African Americans and Hispanics compared to non-Hispanic whites 5
• While fasting glucose and oral glucose tolerance testing may be more sensitive for detecting some at-risk individuals, A1C remains an appropriate and convenient screening tool that reflects average glycemia over 2-3 months 1, 4, 5