Management of Fasting Blood Glucose 6.5 mmol/L (117 mg/dL)
A fasting blood glucose of 6.5 mmol/L (117 mg/dL) indicates prediabetes and requires confirmation with repeat testing, followed by intensive lifestyle modification as first-line therapy, with consideration of metformin for high-risk patients. 1, 2
Confirm the Diagnosis
Repeat testing is essential because fasting glucose has 12-15% day-to-day variability, meaning the same person could measure differently on consecutive days without any actual metabolic change. 1
Obtain a second test using either:
These tests identify different at-risk populations with incomplete concordance, so using FPG alone may underestimate prediabetes prevalence. 1, 4 In fact, FPG testing alone detected only 27.4% of prediabetic cases in one cohort, whereas a complete OGTT detected 87.1%. 4
Risk Stratification
Once prediabetes is confirmed, assess the patient's risk of progression to diabetes:
Approximately 10% of people with prediabetes progress to diabetes annually, but risk is not uniform. 1, 2
Higher-risk patients who benefit most from intervention include:
Additional risk factors to document: first-degree relative with diabetes, high-risk ethnicity (African American, Latino, Native American, Asian American), cardiovascular disease history, hypertension (≥130/80 mmHg), dyslipidemia, polycystic ovary syndrome, physical inactivity, severe obesity, or acanthosis nigricans. 1
First-Line Treatment: Intensive Lifestyle Modification
Lifestyle modification is more effective than medication and should be implemented for all patients with prediabetes. 2
The intervention that has proven efficacy consists of:
- Weight loss goal: 5-7% of body weight 2, 5
- Physical activity: ≥150 minutes per week of moderate activity 2, 5
- Calorie restriction with self-monitoring 2
- Motivational support 2
This approach decreased diabetes incidence by 6.2 cases per 100 person-years over 3 years. 2
Pharmacologic Therapy: Metformin
Metformin should be considered for high-risk patients, particularly those meeting the criteria above (prior gestational diabetes, age <60 with BMI ≥35, FPG ≥110 mg/dL, or HbA1c ≥6.0%). 2
Metformin decreased diabetes risk by 3.2 cases per 100 person-years over 3 years, though this is less effective than lifestyle modification. 2
Important caveat: The effectiveness of interventions for primary prevention has been demonstrated mainly in people with impaired glucose tolerance (IGT) with or without elevated fasting glucose, not for those with isolated impaired fasting glucose (IFG) or prediabetes defined by A1C criteria alone. 1
Ongoing Monitoring
Annual screening is recommended for all patients with confirmed prediabetes. 1
Monitor for cardiovascular risk factors, as prediabetes is associated with increased cardiovascular event rates (excess absolute risk of 8.75 per 10,000 person-years) and mortality (7.36 per 10,000 person-years). 2
Critical Pitfalls to Avoid
Don't panic at borderline values: The 1 mg/dL difference between 99 and 100 mg/dL is clinically arbitrary, reflecting the limitations of using dichotomous cut points for continuous biological variables. 1 Risk increases gradually across the entire "normal" range. 1
Don't rely on fasting glucose alone: HbA1c and OGTT identify different at-risk populations, and using only FPG may miss up to 72.6% of prediabetic cases, particularly in high-risk ethnic groups. 1, 4
Don't use medications as first-line therapy: Lifestyle modification is associated with larger benefit than metformin and should be prioritized. 2
Don't forget to address cardiovascular risk: Prediabetes is not just about diabetes prevention—it's associated with increased cardiovascular events and mortality independent of progression to diabetes. 2