How should I manage a patient with impaired fasting glucose (fasting plasma glucose 100–125 mg/dL)?

Management of Impaired Fasting Glucose (100-125 mg/dL)

Immediately initiate intensive lifestyle modification targeting 7% body weight loss and 150 minutes weekly of moderate physical activity, and strongly consider adding metformin if the patient has BMI >35 kg/m², age <60 years, or history of gestational diabetes. 1

Confirm the Diagnosis First

• Repeat fasting plasma glucose on a different day to confirm the diagnosis, as day-to-day variability is 12-15% 2
• Ensure the patient fasted for at least 8 hours before blood draw 3, 4
• Consider checking HbA1c (prediabetes range: 5.7-6.4%) as it identifies different at-risk populations than fasting glucose alone and has better preanalytical stability 2

Lifestyle Intervention (First-Line, Non-Negotiable)

This is the most effective intervention, superior to any medication. 1

Weight Loss Target

• Achieve 7% reduction from current body weight through reduced caloric intake 1
• This specific target comes from randomized trials showing 58% reduction in diabetes onset over 3 years 1

Physical Activity Prescription

• Minimum 150 minutes per week of moderate-intensity activity (brisk walking where patient can talk but not sing) 1, 5
• Add resistance training at least twice weekly with 8-10 different exercises 1
• Lifestyle modification reduces 2-hour plasma glucose levels (SMD -0.56) and fasting glucose (SMD -0.27) in patients with impaired glucose tolerance 6

Metformin Therapy (Strongly Consider)

Add metformin if any of these criteria are present: 1

• BMI >35 kg/m²
• Age <60 years
• History of gestational diabetes

Metformin delays or prevents diabetes onset, though it is less effective than lifestyle changes 5. The American Diabetes Association specifically recommends considering metformin for persistent impaired fasting glucose meeting these criteria 1.

Cardiovascular Risk Management (Critical Component)

Patients with impaired fasting glucose have elevated cardiovascular risk even before developing diabetes. 1

• Check blood pressure at every visit with target <130/80 mmHg 1
• Screen for dyslipidemia with lipid panel 1
• Consider statin therapy if LDL-C >100 mg/dL in higher-risk patients 1
• The combination of impaired fasting glucose and systolic blood pressure 140-160 mmHg increases 8-year cardiovascular mortality risk 2.10-fold 7

Monitoring Schedule

• Recheck fasting glucose and HbA1c in 4-6 weeks to assess initial response 1
• At least annual monitoring thereafter for progression to diabetes 1
• Screen every 3 years minimum if glucose normalizes 2

Diabetes Prevention Program Referral

• Enroll in a diabetes self-management education and support (DSME/DSMS) program if available 1
• These structured programs provide education and support for sustained behavior change 1

Common Pitfalls to Avoid

• Don't delay intervention waiting to see if glucose "normalizes on its own" - this misses the critical window for preventing diabetes progression 1
• Don't rely on fasting glucose alone - approximately 40% of people who develop diabetes have normal glucose tolerance 5 years before diagnosis, and HbA1c or oral glucose tolerance testing identifies additional at-risk individuals 2, 8
• Don't underestimate cardiovascular risk - impaired fasting glucose with moderate hypertension (140-159 mmHg) increases cardiovascular mortality nearly 3-fold compared to normal glucose 7
• Don't panic at 100 mg/dL vs. 99 mg/dL - the 1 mg/dL difference is clinically arbitrary with 12-15% day-to-day measurement variability; confirm with repeat testing 2

Risk Stratification for Screening Other At-Risk Individuals

Screen additional patients with these risk factors: 5

• Family history of diabetes
• BMI ≥25 kg/m² (≥23 kg/m² in Asian Americans)
• Sedentary lifestyle
• Hypertension or dyslipidemia
• History of gestational diabetes or large-for-gestational-age infant
• Polycystic ovary syndrome
• High-risk ethnicity (Black, Latin American, Native American, Asian-Pacific Islander)