There are many ways for doctors to assess your blood sugar (glucose) and insulin levels and determine insulin resistance. One of the most common methods involves taking an oral "glucose tolerance test."

After fasting, a patient drinks a solution containing 75 grams of sugar glucose. Blood is periodically drawn over a two- to five-hour period to determine how high the glucose levels rise and how quickly they fall. Doctors directly measure changes in glucose and infer insulin function from this data. A glucose response more typical of a diabetic or prediabetic suggests insulin resistance.

Some physicians, especially those who specialize in the treatment of Syndrome X, also draw blood to specifically measure insulin levels, but this is not common in general practice.

A normal fasting glucose range, taken before breakfast, is 65­120 mg/dL (ideal range: 80­100 mg/dL).

A normal fasting insulin range is 6­35 micro-international units per milliliter (mcIU/mL).

A normal two-hour postprandial (postmeal) glucose range is generally 65­139 mg/dL.

A normal two-hour postprandial insulin range is 6­35 micro-international units per milliliter (mcIU/mL).