The teenage years are a challenge for any child as he/she goes through the sexual and emotional changes of puberty. It can be an especially stressful time for adolescents with diabetes; stress makes diabetes worse, and diabetes makes everything more stressful.
Teenagers who followed their diabetes management plans for years may now become rebellious and refuse to comply. They may go through denial and act increasingly aggressively in reaction to the stress of puberty and diabetes.
Blood glucose control gets even harder during these years, perhaps because the growth hormone produced during adolescence negatively affects insulin usage. It's not uncommon for blood glucose levels to swing from too high to too low, adding to the frustration.
This is particularly true for girls around the time of their menstrual period. Hormone fluctuations during the menstrual cycle also affect blood glucose levels. Some girls and women with diabetes notice an increase in blood glucose a few days prior to the beginning of their period and then a decrease after the period begins. In some, the changes are considerable, while others do not notice any difference at all. High blood glucose levels may also cause menstrual periods to be irregular.
Most teens want desperately to "fit in", and being different from peers may be especially stressful in these years. Having to eat meals, test blood glucose, and inject insulin "on time" all violate the desire to conform with one’s peer group. Having diabetes and injecting insulin can have a negative effect on self-image and self-esteem, which are fragile enough during this time.
In short normal teens don't act like adults. Your goal is to help them develop that level of skill and judgment over their teen years.