Impaired Fasting Glucose: When and How to Intervene?

Impaired Fasting Glucose: When and How to Intervene?

My 46-year-old patient had a fasting plasma glucose level of 115 mg/dL; a followup fasting plasma glucose level was 116 mg/dL. A year earlier, his fasting glucose level was 103 mg/dL and urinalysis results were negative. The patient is tall; his body mass index (BMI) is 25 kg/m2 He has no significant medical history; however, his maternal grandmother and aunt both had type 2 diabetes.

The patient appears to have impaired glucose tolerance-although I have not yet received the results of tests for glycosylated hemoglobin and microalbumin. Should I simply follow this patient with occasional fasting glucose levels, order a glucose tolerance test, or begin treating him for diabetes?

This case raises at least 3 questions:

  • Does the patient have diabetes mellitus?
  • If so, which type?
  • What treatment, if any, is require
Does the patient have diabetes? The diagnosis of diabetes can be made if 1 of the following 3 criteria is met:
  • The fasting plasma glucose level is at least 126 mg/dL.
  • The patient has symptoms of diabetes and a casual (measured at any time of day) plasma glucose level of 200 mg/dL or above.
  • The plasma glucose level is 200 mg/dL or greater 2 hours after administration of a 75-g oral glucose dose.1

Fasting plasma glucose levels of 115 mg/dL and 116 mg/dL do not meet the diagnostic criteria for diabetes. Instead, patients with these values have impaired fasting glucose. Such patients are at high risk for later development of overt diabetes.

What type of diabetes would be most likely? A family history such as this man's suggests type 2 diabetes. However, a BMI of 25 kg/m2 and a relatively slender body habitus raise the possibility of type 1 diabetes. Since we now know that this disease can begin at any age, I suspect that type 1 diabetes would eventually develop, necessitating insulin therapy. Is treatment recommended? The American Diabetes Association recommends the following treatment goals for all persons with diabetes:

  • Preprandial blood glucose level between 80 and 120 mg/dL.
  • Bedtime blood glucose level between 100 and 140 mg/dL.
  • Hemoglobin A1c less than 7% in an assay in which the upper limit of normal is 6%.2

I suspect that all values for a patient such as this man would be within the goal ranges. Thus, I would not initiate treatment at this point. Rather, I would teach the patient how to monitor blood glucose levels at home and follow closely. An oral glucose tolerance test would not be useful.
John P. Bantle, MD
  Professor of Medicine
  Division of Endocrinology and Diabetes
  University of Minnesota School of Medicine

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