Protocol for glucose tolerance test

Preparation for the test

Ideally, the patient should eat a high carbohydrate diet for three days prior to the test. See the patient information leaflet for further help with the diet.

The patient should fast for at least 11 hours prior to the test. Therefore, if the test is to commence at 9am, nothing other than water should be taken from 10pm on the prior evening.

Test protocol

  1. A sample of venous blood should be taken into a labelled fluoride tube (grey top). This is the fasting glucose sample.
  2. The patient should be given 113ml Polycal, diluted with approximately 200ml water. This provides the correct load of 75g of glucose. This glucose
    load should be completely consumed within a few minutes.
  3. For children, 2.64ml/kg should be given up to a maximum of 113ml.
  4. During the two hours of the test, the patient should remain at rest and must not smoke or eat. Drinks of water only may be permitted.
  5. After exactly 120 minutes, a second sample of venous blood should be taken into a labelled fluoride tube (grey top). This is the two hour post-load glucose sample.
  6. Both blood glucose samples should be sent together and must be clearly labelled with the name and date of birth of the patient.
  7. Do not forget to write the time (0 and 120 min) of the sample. If any of this information is missing, the samples may be rejected. They should then accompany the completed request form to the laboratory.

Please ensure that all therapy being taken by the patient is stated on the form, as this may affect the interpretation of the results.

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