Diabetes Mellitus: Screening and Diagnosis.

Diabetes mellitus is one of the most common diagnoses made by family physicians. Uncontrolled diabetes can lead to blindness, limb amputation, kidney failure, and vascular and heart disease. Screening patients before signs and symptoms develop leads to earlier diagnosis and treatment, but may not reduce rates of end-organ damage. Randomized trials show that screening for type 2 diabetes does not reduce mortality after 10 years, although some data suggest mortality benefits after 23 to 30 years. Lifestyle and pharmacologic interventions decrease progression to diabetes in patients with impaired fasting glucose or impaired glucose tolerance. Screening for type 1 diabetes is not recommended. The U.S. Preventive Services Task Force recommends screening for abnormal blood glucose and type 2 diabetes in adults 40 to 70 years of age who are overweight or obese, and repeating testing every three years if results are normal. Individuals at higher risk should be considered for earlier and more frequent screening. The American Diabetes Association recommends screening for type 2 diabetes annually in patients 45 years and older, or in patients younger than 45 years with major risk factors. The diagnosis can be made with a fasting plasma glucose level of 126 mg per dL or greater; an A1C level of 6.5% or greater; a random plasma glucose level of 200 mg per dL or greater; or a 75-g two-hour oral glucose tolerance test with a plasma glucose level of 200 mg per dL or greater. Results should be confirmed with repeat testing on a subsequent day; however, a single random plasma glucose level of 200 mg per dL or greater with typical signs and symptoms of hyperglycemia likely indicates diabetes. Additional testing to determine the etiology of diabetes is not routinely recommended.