Diagnosis of Diabetes

The diagnosis of diabetes can be made in one of the following three methods but each must be confirmed on a subsequent day:

• Presence of symptoms of diabetes and a random blood glucose value of ≥200 mg/dL

• Fasting plasma glucose ≥126 mg/dL

• Two-hour plasma glucose ≥200 mg/dL during an oral glucose tolerance test (OGTT)

The OGTT is carried out after an overnight fast of 8–10 h following 3 days of adequate carbohydrate intake (>150 g/day). After taking an initial fasting blood sample, a 75g load of oral glucose dissolved in 250 mL of water is given and the blood sample is collected again 2 h after the drink.

In addition, the glycosylated hemoglobin (HbA_1c) may be used to diagnose diabetes although it is not specifically recommended as a diagnostic test for DM. A HbA_1c level of 1% above the upper range of normal reference value is suggestive of diabetes and has a specificity of 98%.¹

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Written by: Healthplus24 team
Date last updated: July 13, 2011