An elevation of blood glucose level above the upper limit of its reference range is referred to as hyperglycemia.
Hyperglycemia is graded as follows:
- Impaired fasting glucose: elevation of blood glucose above the upper limit of the fasting reference range of 60 to 110 mg/dl (3.3 - 6.1 mmol/l) but below 200 mg/dl (11 mmol/l).
- Pathological gucose tolerance: elevation of glucose levels above the maximum permissible value for glucose tolerance test (140 mg/dl or 7.8 mmol/l) but below 200 mg/dl (11 mmol/l).
- Diabetes mellitus: Elevation of glucose level above 200 mg/dl (11 mmol/l) postprandial or above 120 mg/dl (6,7 mmol/l) fasting.
True hyperthyroidism by exceeding function of the thyroid gland is used to be distinguished from thyrotoxicosis by exogenously supplied thyroxine, e. g. by misdosage (Thyreotoxicosis factitia).