Diabetes is diagnosed if blood sugar readings are above certain internationally agreed-upon levels (“thresholds”). Because blood sugar levels tend to go up and back down again after a meal, for example, the threshold varies depending on how long ago you last ate.
It is important to note that the diagnosis is usually only confirmed if at least two different blood sugar readings are too high. But if you also have typical symptoms (like extreme thirst), one clearly too-high reading is already enough.
Sugar molecules can bind to the red pigment in your blood known as hemoglobin. Your HbA1c value shows how much of your hemoglobin has been changed in this way. It is a measure of your average blood sugar level over the last 8 to 12 weeks. People with an HbA1c over 6.5% are considered to have diabetes.
Random glucose test
Glucose tolerance test
The oral glucose tolerance test (OGTT) measures how well your body can process sugar. It is done if the results of other tests aren’t clear or if you have a high risk of developing diabetes. First, you drink a glass of water with 75 grams of sugar (glucose) dissolved in it. This makes your blood sugar levels rise, but they should go back down quite quickly after that. If they’re still above 200 mg/dL (11.1 mmol/L) after two hours, you’re diagnosed with diabetes.
Bundesärztekammer (BÄK), Kassenärztliche Bundesvereinigung (KBV), Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften (AWMF). Nationale Versorgungsleitlinie: Therapie des Typ-2-Diabetes. S3-Leitlinie. AWMF-Registernr.: nvl-001g. 2023.
Petersmann A, Müller-Wieland D, Müller UA et al. Definition, Classification and Diagnosis of Diabetes Mellitus. Exp Clin Endocrinol Diabetes 2019; 127(S 01): S1-S7.
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