Generally if a child shows symptoms of diabetes, then the physician will order a glucose tolerance test. This test will show how the blood reacts to a sugary drink.
If the doctor thinks the child has diabetes based on symptoms such as weight loss, fatigue, frequent urination, and extreme hunger, he will give him a random blood sugar test.
Your doctor will probably instruct you to have your child refrain from food after midnight and then take the child for a blood test early the next morning.
The test most often used is the blood glucose test. Specifically the fasting blood glucose test. This involves not eating anything after midnight the day before the test and then coming in and having blood drawn and tested.