What is the dawn phenomenon that some people with diabetes experience? Can anything be done about it?
Answers from M. Regina Castro, M.D.
The dawn phenomenon, also called the dawn effect, is the term used to describe an abnormal early-morning increase in blood sugar (glucose) — usually between 2 and 8 a.m. — in people with diabetes.
Some researchers believe the natural overnight release of the so-called counter-regulatory hormones — including growth hormones, cortisol, glucagon and epinephrine — increases insulin resistance, causing blood sugar to rise. High morning blood sugar may also be caused by insufficient insulin the night before, insufficient medication dosages or carbohydrate snack consumption at bedtime.
If you have persistently elevated blood sugar in the morning, checking your blood sugar once during the night — around 2 or 3 a.m. — for several nights in a row will help you and your doctor determine if you have the dawn phenomenon or if there's another reason for an elevated morning blood sugar reading.
What you can do
Your doctor may recommend a number of options to help you prevent or correct high blood sugar levels in the morning:
- Avoid carbohydrates at bedtime.
- Adjust your dose of medication or insulin.
- Switch to a different medication.
- Adjust the time when you take your medication or insulin from dinnertime to bedtime.
- Use an insulin pump to administer extra insulin during early-morning hours.
M. Regina Castro, M.D.
Oct. 23, 2014
- Gardner DG, et al. Greenspan's Basic & Clinical Endocrinology. 9th ed. New York, N.Y.: The McGraw-Hill Companies; 2011. http://accessmedicine.mhmedical.com/book.aspx?bookId=380. Accessed Sept. 9, 2014.
- King AB, et al. Contribution of the dawn phenomenon to the fasting and postbreakfast hyperglycemia in type 1 diabetes treated with once-nightly insulin glargine. Endocrine Practice. 2012;18:558.
- Melmed S, et al. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. https://www.clinicalkey.com. Accessed Sept. 9, 2014.