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Patient information on glucose tolerance tests

This test excludes or confirms the diagnosis of diabetes.

For three days prior to the test you must eat a high carbohydrate diet. The following foods give 1 portion of carbohydrate. You should eat at least 10 of these portions spread across the day.

Bread (white/brown/wholemeal)
1 small or 1/2 large roll
1/2 small pitta bread
1/2 6" chapatti
1/2 teacake
1/2 English muffin
1 crumpet
1/2 bagel

Breakfast cereals
1 Shredded Wheat/Weetabix
25g (4 tbsp) high fibre cereal
e.g branflakes
20g (2 tbsp) porridge oats

20g uncooked
75g cooked

20g uncooked
100g cooked

15g uncooked (1 tbsp) / 50g cooked

100g raw/boiled/mash
50g roast/chips/baked

11/2 digestive/hob nobs
3 digestive fingers
3 rich tea
2 crackers e.g. Ryvita
1 cereal bar

1 apple/pear/orange/firm banana
2 kiwi/Satsuma/plums
20g dried fruit
100g fruit salad
4 fl oz. (110 ml) fruit juice

1 pot dried fruit flavoured or plain yoghurt
1/4 large tin of low fat rice pudding (110g)
1/3 packet (made up) sugar free whip.

1 small packet crisps
1/2 pint milk

Example of day's intake (portions)

2 weetabix with milk (2)
1 slice toast (1)
1 fruit juice (4 fl.oz/110 ml) (1)

Light meal
2 slices bread/sandwich with ham/cheese/fish (2)
Fruit (1)
Crisps (1)

1 1/2 digestive biscuit (1)

Main meal
Meat/Fish etc.
3 egg size potatoes (1)

Total 10

You may have more starchy foods than this, please try not to have less.

On the night before the test

After 10pm the night before the test please do not have anything to eat and only plain water to drink, so that you arrive for your test fasting.

The test

The test will take about two hours. When you arrive for the test a blood sample will be taken. You will be given a glass of glucose to drink. A further blood sample will be taken after twohours. During the two hours you can drink plain water, but should not eat or smoke.

Once the test is completed, the results will be sent to your doctor.

Side effects

Occasionally patients feel light headed or dizzy about 1/2 hour after drinking the glucose. This passes very quickly. As the test takes two hours to complete, please bring something to read/do. You will be required to remain in the unit for the duration of the test. As space is limited we regret that it is not possible to bring a child or relative with you.

If you are unable to attend, please call Epsom pathology laboratory on 01372 73 5735 ext 6095 as soon as possible so that your appointment can be offered to someone else.

If you have any questions or problems regarding the above, please do not hesitate to contact us.


  • follow the high carbohydrate diet for three days before the test;

  • make sure you arrive for the test fasting;

  • bring something to read.