Some patients with impaired fasting glucose also may be diagnosed with impaired glucose tolerance, but many have normal responses to a glucose tolerance test. Fasting glucose is helpful in identifying prediabetes when positive but has a risk of false negatives.World Health Organization (WHO) criteria for impaired fasting glucose differs from the American Diabetes Association (ADA) criteria, because the normal range of glucose is defined differently by each. Fasting plasma glucose levels 100 mg/dL (5.5 mmol/L) and higher have been shown to increase complication rates significantly, however, WHO opted to keep its upper limit of normal at under 110 mg/dL for fear of causing too many people to be diagnosed as having impaired fasting glucose, whereas the ADA lowered the upper limit of normal to a fasting plasma glucose under 100 mg/dL. WHO criteria: fasting plasma glucose level from 6.1 mmol/L (110 mg/dL) to 6.9 mmol/L (125 mg/dL)
ADA criteria: fasting plasma glucose level from 5.6 mmol/L (100 mg/dL) to 6.9 mmol/L (125 mg/dL)

Impaired glucose tolerance
Impaired glucose tolerance (IGT) is diagnosed with an oral glucose tolerance test. According to the criteria of the World Health Organization and the American Diabetes Association, impaired glucose tolerance is defined as:
two-hour glucose levels of 140 to 199 mg per dL (7.8 to 11.0 mmol/L) on the 75-g oral glucose tolerance test. A patient is said to be under the condition of IGT when he/she has an intermediately raised glucose level after 2 hours, but less than the level that would qualify for type 2 diabetes mellitus.
Having an additional screening option in the dental setting may offset some of the emotional struggle because it is more regularly visited and therefore has the potential to initiate earlier recognition and intervention. Prediabetes screening in a dental setting
Its been found that people will visit their dentist more regularly than their primary physician for checkups, so the dentists office becomes a very useful place for potentially checking for diabetes. For people who are unaware of their diabetes risk and fall into the non-White, obese, or ≥45 y old category, screening at the dentists would have the highest odds of getting identified as someone at risk. Studies have been done to evaluate the overall effectiveness and value of prediabetes testing in the dental setting, usually at dental schools. One study has looked at screening through dental visits followed up by intervention programs such as the commercial Weight Watchers and found it a cost-effective means to identify and treat affected people in the long term. Cost is a factor people at risk might need to consider, since, on average, people diagnosed with diabetes have approximately 2.3 times higher medical expenditure that what expenditures would be in its absence.A simple test may be instituted at the dentists office, in which an oral blood sample is taken during a normal visit to the dentists. This sample tests for glycated hemoglobin (HbA1c) levels; HbA1c gives healthcare professionals an idea of blood glucose levels and is the most reliable form of testing for diabetes in asymptomatic patients.