Impaired glucose tolerance (IGT) is a condition where blood glucose levels are higher than normal but not high enough to be diagnosed as diabetes. It is defined as two-hour glucose levels of 140 to 199 mg per dL (7.8 to 11.0 mmol) on the 75-g oral glucose tolerance test. Impaired fasting glucose (IFG) is another condition that is similar to IGT, but it is defined as glucose levels of 100 to 125 mg per dL (5.6 to 6.9 mmol per L) in fasting patients. Patients with IGT or IFG are at significant risk for developing diabetes and cardiovascular disease. Risk factors for diabetes include family history of diabetes, body mass index greater than 25 kg per m2, sedentary lifestyle, hypertension, dyslipidemia, history of gestational diabetes or large-for-gestational-age infant, and polycystic ovary syndrome.

To diagnose IGT, a 75-g oral glucose tolerance test is recommended. The American Diabetes Association recommends a screening interval of every three years in the absence of risk factors beyond age alone, whereas a shorter screening interval is recommended for persons at higher risk. When the diagnosis of IGT or IFG is made, physicians should counsel patients to lose 5 to 7 percent of their body weight and engage in moderate physical activity for at least 150 minutes per week. Eating a healthy, balanced diet is also a key way of treating IGT.