• Usually asymptomatic (found on screening exam)

  • Medication use

    – Drug-induced hyperglycemia may occur with: thiazide-type diuretics (high doses); beta blockers; protease inhibitors; atypical antipsychotics; corticosteroids; niacin; pentamidine; phenytoin
; sympathomimetic drugs

  • Medical history (ask about)

    – Hypertension, hyperlipidemia, obesity

    – Recurrent yeast infections 

    – Renal disease, eye disease, neuropathy, heart disease 

    – History of gestational diabetes, PCOS, delivery of infant with macrosomia 

  • Family history of diabetes, coronary artery disease, kidney disease, or eye or retinal disease

  • Diet, exercise, substance use


Physical examination

  • Funduscopic exam 

  • Foot exam (tinea, ulceration)

  • Distal sensation and proprioception 

Making the diagnosis 

  • Diagnosis based on any of 

    -Two-hour 75 g oral glucose tolerance test levels 
140-199 mg/dL 

    – Fasting plasma glucose levels 100-125 mg/dL 

    – HbA1c levels 5.7%-6.4% 

  • Capillary glucose may be approximately 10% higher than venous glucose. 

Rule out 

  • Drug-induced hyperglycemia 

  • Systemic metabolic disorder

    – Cushing syndrome 

    – Hyperthyroidism

  • Liver disease

Testing to consider 

  • Fasting plasma glucose 

  • HbA1c
  • Oral glucose tolerance test 

  • Metabolic panel

  • Liver function tests

  • Thyroid-stimulating hormone

Lifestyle changes

  • Dietary changes might reduce incidence of type 2 diabetes for patients with IGT.

  • Selected foods associated with reduced risk for diabetes 

    – Whole grains: Brown rice may decrease and white rice may increase diabetes risk 

    – Nuts and peanut butter 

    – Dairy (especially low-fat) 

    – Green vegetables, fruits and berries, margarine and oil, and poultry 

    – Caffeinated coffee

    -Associations of reduced risk for diabetes with fruit and vegetable intake less consistent 

  • High-fiber, low-fat diet associated with sustained weight reduction and reduced incidence of diabetes

  • Lifestyle changes can reduce incidence of diabetes more effectively than can metformin or placebo.

  • Structured education program with pedometer may be effective for improving glucose tolerance.

  • Lifestyle changes (with considerable support) can reduce risk for type 2 DM in patients with IGT.

    – Results sustained over seven years 

    – 10-year mortality and cardiovascular morbidity not significantly different


  • Lifestyle and pharmacologic interventions reduce rate of progression to type 2 DM in patients with IGT.

  • Antidiabetic agents that each appear to reduce rate of progression to type 2 DM 

    – Biguanides (metformin): Metformin reduces incidence of new-onset diabetes in patients with prediabetes.
  – Alpha-glucosidase inhibitors (acarbose, voglibose): with acarbose
 there is evidence for delay of progression to diabetes mixed
 and high rate of side effects; with voglibose reduces development of type 2 DM in high-risk patients. 

    – Thiazolidinediones (rosiglitazone, pioglitazone): Rosiglitazone reduces incidence of diabetes in patients with IGT and no cardiovascular disease, but increases risk of heart failure (use restricted in the United States).
Pioglitazone may delay onset of type 2 DM (use restricted in Europe).

    – Combination therapies
: Low-dose combination metformin and rosiglitazone reduces progression to type 2 DM. 

  • Other agents

    – Orlistat
: may reduce incidence of type 2 DM
; may prevent or improve IGT in obese adults 

    – ACE inhibitors and angiotensin receptor blockers
: may reduce risk for new-onset type 2 DM; in patients with IGT, valsartan may reduce diabetes but no differences in cardiovascular outcomes. 

Herbs and supplements

  • Agents that may improve fasting plasma glucose

    – Chinese herbal medicines

    – Opuntia ficus-indica
  • Agents without documented effect

    – Chromium supplementation 

    – Ginkgo biloba extract (EGb 761) 


Screening and prevention

  • Screening for prediabetes followed by lifestyle intervention in overweight and obese patients is cost-effective.

  • Recommendations for screening
 from the American Diabetes Association
    – Adults older than age 45 years 

    – Adults of any age if overweight or obese (BMI ≥ 25) with any high-risk features for diabetes

    – Overweight children older than age 10 years (or after puberty onset if earlier) with two or more of the following: 
family history
; signs or conditions associated insulin resistance (acanthosis nigricans, hypertension, dyslipidemia or PCOS); maternal history of diabetes/gestational diabetes; ethnic group at increased risk 

    – Repeat screening every three years if normal, or every year if at increased risk for future diabetes 

  • Recommendations for screening from the United States Preventive Services Task Force
    – Adults with BP >135/80 mm Hg
  • From the Canadian Task Force on Preventive 
Health Care 

    – Adults with hypertension or hyperlipidemia.

Alan Drabkin, MD, is a clinical editor for DynaMed, a database of comprehensive updated summaries covering more than 3,200 clinical topics, and an assistant clinical professor of population medicine at Harvard Medical School.

Robert K. Smitherman, MD, practices internal medicine at Medical Clinic of North Texas and a peer reviewer for DynaMed.