Diabetes Symptom

The fasting plasma glucose test is the preferred test for diagnosing type 1 or type 2 diabetes and is most reliable when done in the morning. However, a diagnosis of diabetes is made for any one of three positive tests, with a second positive test on a different day:

A random plasma glucose value (taken any time of day) of 200 mg/dL or more, along with the presence of diabetes symptoms.

A plasma glucose value of 126 mg/dL or more, after a person has fasted for 8 hours.

An oral glucose tolerance test (OGTT) plasma glucose value of 200 mg/dL or more in the blood sample, taken 2 hours after a person has consumed a drink containing 75 grams of glucose dissolved in water. This test, taken in a laboratory or the doctor’s office, measures plasma glucose at timed intervals over a 3-hour period.

Gestational diabetes is diagnosed based on plasma glucose values measured during the OGTT. Glucose levels are normally lower during pregnancy, so the threshold values for diagnosis of diabetes in pregnancy are lower. If a woman has two plasma glucose values meeting or exceeding any of the following numbers, she has gestational diabetes: a fasting plasma glucose level of 95 mg/dL, a 1-hour level of 180 mg/dL, a 2-hour level of 155 mg/dL, or a 3-hour level of 140 mg/dL.