This patient support community is for questions related to juvenile diabetes including celiac disease, depression, diabetic complications, hyperglycemia / diabetic keto-acidosis, hypoglycemia, islet cell transplantation, nutritional issues, parenting a diabetic child, pregnancy, pump therapy, school issues, and teens with diabetes.
Here is a good explanation offered by someone at UCSD:
http://www.faqs.org/faqs/diabetes/faq/part2/section-13.html
While I'm not a physician (no one here is), I've learned how to "test" what's going on. It does require at least one night of rather interrupted sleep. The test is to do several blood tests during the night & early morning to record the results.
Bedtime
Midnight
2am
4am
6am
wake up time
Do this test on a night when you've had a meal that's typical for you and not particular loaded with fats. It's ideal if you can go to bed with a fairly normal blood sugar. Record your results. If the results are not what you think is typical, then repeat the test a few days later after catching up on good sleep ;-)
Call your doc with the results and discuss treatment options. I'm assuming you're a Type 1, and so your doc's approach will likely involve adjusting dose & timing of your long-acting insulin -- finding the balance that won't drive you too low.
For Type 2s with a dawn phenomemon, a good strategey is to have a bedtime snack that includes a good dose of protein (metabolized more slowly than carbos). This snack seems to ease that dawn phenomenon. I was told that this approach does not work for us Type 1s.