What are the threshold values for Fasting Blood Sugar (FBS), 2-Hour Postprandial Plasma Glucose (2HPP), and Hemoglobin A1c (HbA1c) to initiate antidiabetic medication?

From the Guidelines

Antidiabetic medication is typically started when fasting blood sugar (FBS) is ≥126 mg/dL, 2-hour postprandial glucose (2hpp) is ≥200 mg/dL, or HbA1c is ≥6.5%. The American College of Physicians recommends that clinicians should aim to achieve an HbA1c level between 7% and 8% in most patients with type 2 diabetes 1. The following are key points to consider:

• Threshold values: FBS ≥126 mg/dL, 2hpp ≥200 mg/dL, or HbA1c ≥6.5% are commonly used thresholds to initiate antidiabetic medication.
• Individualization of treatment: Treatment should be individualized based on patient factors, comorbidities, and preferences.
• Initial treatment: For most adults, initial treatment usually begins with metformin, starting at 500 mg once or twice daily with meals.
• Monitoring and adjustment: Regular monitoring of blood glucose and HbA1c is essential to assess treatment efficacy and adjust therapy as needed.
• Considerations for specific populations: For patients with a life expectancy less than 10 years, limited life expectancy, or increased risk for hypoglycemia, less stringent HbA1c targets may be appropriate. These recommendations are based on the latest evidence from the American College of Physicians and other reputable sources, including the American Diabetes Association 1 and the U.S. Department of Veterans Affairs/U.S. Department of Defense clinical practice guideline 1.

From the Research

Threshold Values for Antidiabetic Medication

The threshold values for Fasting Blood Sugar (FBS), 2-Hour Postprandial Plasma Glucose (2HPP), and Hemoglobin A1c (HbA1c) to initiate antidiabetic medication are as follows:

• Fasting Plasma Glucose (FPG):
  • 126 mg/dL or higher, as indicated by 2 and 3
  • 110-125 mg/dL is considered impaired fasting glucose, as stated in 3
• 2-Hour Postprandial Plasma Glucose (2HPP):
  • 200 mg/dL or higher, as indicated by 2
  • 160-199 mg/dL may be considered impaired glucose tolerance, as suggested by 4 and 5
• Hemoglobin A1c (HbA1c):
  • 6.5% or higher, as indicated by 2
  • 6.0-6.4% may be considered prediabetic or at risk for diabetes, as suggested by 3 and 6

Relationship Between FPG, 2HPP, and HbA1c

The relationship between FPG, 2HPP, and HbA1c is complex, with each measure providing unique information about glucose control:

• FPG is a measure of basal glucose levels, while 2HPP reflects postprandial glucose spikes, as discussed in 4 and 5
• HbA1c provides a measure of average glucose control over the preceding 2-3 months, as indicated by 2 and 6
• The contribution of FPG and 2HPP to HbA1c varies, with 2HPP contributing more to HbA1c in individuals with good glucose control, as suggested by 4 and 5

Clinical Implications

The choice of threshold values for initiating antidiabetic medication depends on various factors, including the presence of symptoms, comorbidities, and the risk of complications:

• Individuals with FPG ≥ 126 mg/dL, 2HPP ≥ 200 mg/dL, or HbA1c ≥ 6.5% may be considered for antidiabetic medication, as indicated by 2 and 3
• Those with impaired fasting glucose or impaired glucose tolerance may benefit from lifestyle modifications and close monitoring, as suggested by 3 and 6