Blood laboratory levels can be affected by food. Therefore, the patient cannot eat before the test. He / she man drink only water eight to 12 hours before the test.
On the day of the test, the patient drinks a sweet beverage. Blood is obtained and tested before and at 30-minute intervals (for up to three hours) after drinking it to measure glucose (and insulin, if required) levels over time.
- Upon arrival, the patient may have a height and weight measurement.
- A small needle will be used to take blood from a vein. The blood is tested. Most often, this vein is in a hand or arm. Some patients complain of pain when the needle is placed. Others describe a prick or stinging sensation. A skin-numbing cream can sometimes be used to eliminate pain, if planned in advance.
- The patient is then given a very sweet drink. It is important to finish this drink in five minutes.
- Blood is tested at 30-minute intervals (for up to three hours) after finishing the drink.
- When the test is finished, the patient is given a meal of his / her choice.