NHS Grampian output the following:
75g Oral Glucose Tolerance Test
It can easily be performed in primary care but a standardised protocol must be followed and laboratory glucose analysis must be used. This test should not be performed during intercurrent illness. On rare occasions two oral glucose tolerance tests may need to be performed before a diagnosis of diabetes can be confirmed.
The patient should maintain an adequate carbohydrate intake (> 150g) for at least three days prior to the test.
Fast overnight for a minimum of 10 hours (water only permitted).
75 g oral glucose dissolved in 250 to 300ml water to be consumed in no more than 5 minutes followed by a further 100mls water.
Acceptable alternatives are;
Lucozade 394ml (73kcal/100ml formulation) or 410 mls (70Kcal/100ml formulation )
Please note that until the end of 2007 there potentially will be two types of lucozade available
Maltodextrins in appropriate volume to provide 75g carbohydrate (e.g. Calsip 150ml)
Blood for glucose estimation to be taken before (zero minutes) and 120 minutes after consumption of the drink.
Urine may also be tested for glucose to estimate the renal threshold, but this does not contribute to the diagnosis of diabetes, which is based on the fasting and two-hour blood glucose results.
The method of blood sampling is important and must be specified: venous or capillary, plasma or whole blood. Venous plasma is most commonly used. (Aberdeen Diabetic Clinic uses capillary glucose).
The patient should remain sedentary and not smoke, eat or drink for the duration of the test.
Interpretation of 75g Oral Glucose Tolerance Test (WHO 2000)
Glucose (mmol/l) Fasting 2 Hour
Diabetes Mellitus
11.1Venous Plasma
12.2Capillary Plasma
Impaired Glucose Tolerance
Venous Plasma < 7.8,7.0 and < 11.1
Capillary Plasma < 8.9,7.0 and < 12.2
