Cause

You have type 1 diabetes because your pancreas can no longer produce insulin. When your pancreas was working, it adjusted the amount of insulin it made based on your changing blood sugar. But insulin injections cannot control your blood sugar moment to moment, as your pancreas would. As a result, you will have high and low blood sugar levels from time to time.

Causes of high blood sugar

• Skipping a dose of insulin.
• Eating more food than usual.
• Stress and being ill (such as with severe flu) or having an infection, especially if you are not eating or drinking enough
• Taking medicines that can raise blood sugar levels, such as those for sleep, some decongestants, and corticosteroids (such as prednisone)
• The dawn phenomenon or the Somogyi effect, which can cause early-morning high blood sugar
• Adolescence, because of hormone changes and rapid growth

Causes of low blood sugar

• Taking too much insulin
• Skipping or delaying a meal or snack
• Exercising more than usual without eating enough food
• Drinking too much alcohol, especially on an empty stomach
• Taking medicines that can lower blood sugar, such as aspirin and medicines for mental disorders
• Starting your menstrual period, because hormonal changes may affect how well insulin works