oral glucose tolerance test

Why is this done?

  • For diagnosis of diabetes mellitus in case of diagnostic uncertainty
  • useful in patients with abnormal haemoglobin / pregnancy

Prerequisites

  1. The person should be on a normal carbohydrate diet for the preceding 3 days
  2. The person must fast from 12 midnight the previous night
  3. water is permitted
  4. Please avoid alcohol the previous evening/ night

Requirements

  1. 75 g anhydrous glucose.
  2. Fluoride oxalate tubes for glucose.
  3. EDTA (purple) tubes
  4. Clotted red or yellow tubes
  5. 20g i.v. cannula.
  6. Saline flush.
  • Patient arrives fasting at 8 AM
  • Patient should not exercise or smoke during the test
Bloods Procedure Comments
– 15 min Glucose

 

 Insert canula

Prepare glucose solution with

75 grams of glucose in water
T +0 min Patient drinks glucose solution in

10 min
T + 1 hour Glucose Finger prick test

Glucose _____
T + 2 hours Glucose Ask patient for any symptoms

__________________

 

 Finger prick test

Glucose _____

 

INTERPRETATION

In non pregnant state

Fasting glucose > 7.0 mmol/l or 2 hour post glucose >11.1 mmol/l constitutes diabetes

 

Ajith George