What it means
The client fasts for at least 8 hours, has a fasting blood glucose drawn, drinks a set amount of glucose (75 g for the standard adult test) and has blood drawn again, usually at 2 hours. It shows how well the body handles a sugar load and is used to diagnose diabetes, prediabetes and diabetes of pregnancy. In pregnancy, screening is usually done at 24 to 28 weeks, sometimes in two steps with a 50 g drink first.
For the nurse
Teach the client to fast beforehand, to stay seated and not to eat, smoke or exercise during the test, since these change the result. Watch for feeling faint or sweaty after the drink.
At a glance
| Normal range | 2-hour value below 140 mg/dL [below 7.8 mmol/L] (adult, 75 g, not pregnant); 140–199 mg/dL [7.8–11.0 mmol/L] is prediabetes and 200 mg/dL [11.1 mmol/L] or higher is diabetes. |
|---|---|
| Abbreviations | OGTT |
| Spanish | prueba de tolerancia oral a la glucosa |
| Also written | oral glucose tolerance tests, glucose tolerance test, OGTT |
Related terms
diabetes mellitus
A long-term disease in which blood glucose stays high because the body makes too little insulin or cannot use it well.
blood glucose
The amount of sugar (glucose) in the blood at the time it is measured.
gestational diabetes
High blood sugar that first develops during pregnancy in a person who did not have diabetes before.
prediabetes
Blood sugar levels that are higher than normal but not yet high enough to be called diabetes.