How is diabetes mellitus detected?

Professionals have agreed internationally on certain blood glucose levels, from which the diagnosis of diabetes is made. For example, as the blood glucose level rises sharply after a meal and then drops, the threshold also depends on how long the last meal has been.

Fasting blood sugar

This measurement takes place, for example, in the morning before breakfast. The diagnosis of diabetes is made when the fasting blood glucose level repeatedly exceeds 126 mg / dL (corresponds to 7 mmol / L).

Glucose tolerance test

How well the body can process sugar can also be determined by a so-called oral glucose tolerance test (oGTT). You drink a glass of water in which 75 grams of glucose are dissolved. After that, the blood sugar rises but should fall quickly again. The diagnosis of diabetes is made when the blood sugar after two hours is still over 200 mg/dl (equivalent to 11.1 mg / L).

opportunity measurement

The blood glucose value is often also determined when blood was taken for other reasons. Diabetes is suspected if glucose is above 200 mg / dL (equivalent to 11.1 mg / L) on such occasional measurements. As a rule, physicians then propose the measurement of fasting blood glucose or a glucose stress test for review.


HbA1c is a part of the red blood pigment (hemoglobin) to which sugar molecules can adhere. The HbA1c value indicates how high blood glucose has been on average in the last three months. The diagnosis of diabetes is made when the HbA1c value is above 6.5%.


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