This site is intended for healthcare professionals
General Practice Notebook
Login | Register
Medical search

oral glucose tolerance test

FREE subscriptions for doctors and students... click here
You have 3 open access pages.

In the oral glucose tolerance test the patient, after fasting for 15 hours, drinks 75 g of glucose in 300 ml of water, over 5 minutes. Blood glucose is measured before the drink and after 30, 60, 90 and 120 minutes. Urine is collected before the drink, and after 60 and 120 minutes. Before the test, for a period of 6 hours, the patient should avoid smoking and drinking coffee.

There is a normal glucose tolerance if the venous plasma value is less than 7.8 mmol/l after the 2 hour period, i.e. diabetes and impaired glucose tolerance are excluded.

If after 2 hours after the glucose load the value is >=7.8 and <= 11 mmol/l, then there is impaired glucose tolerance.

If glucose is greater than or equal to 11.1 mmol/l, diagnose diabetes mellitus, if symptoms are present; in asymptomatic patients, a further value greater than or equal to 11.1 mmol/l during the oral glucose tolerance test is required.

If the blood glucose reaches its highest level at 30 min and then falls below normal levels at 60 and 90 min then this is a lag curve. This profile is due to rapid glucose absorption followed by a burst of insulin production which over-compensates, resulting in hypoglycaemia.

If the blood glucose rises only a small amount, this is called a flat profile.


General Practice Notebook
General Practice Notebook
The information provided herein should not be used for diagnosis or treatment of any medical condition. A licensed medical practitioner should be consulted for diagnosis and treatment of any and all medical conditions. Copyright 2016 Oxbridge Solutions LtdĀ®. Any distribution or duplication of the information contained herein is strictly prohibited. Oxbridge Solutions LtdĀ® receives funding from advertising but maintains editorial independence. GPnotebook stores small data files on your computer called cookies so that we can recognise you and provide you with the best service. If you do not want to receive cookies please do not use GPnotebook.