What is the dawn phenomenon that some people with diabetes experience? Can anything be done about it?
Answer 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 a.m. and 8 a.m. — in people with diabetes.
Some researchers believe the natural overnight release of the so-called counter-regulatory hormones — including growth hormone, 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 anti-diabetic 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 a.m. 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.
- Change 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.
Nov. 13, 2020
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See more Expert Answers
- Gardner DG, et al., eds. Pancreatic hormones and diabetes mellitus. Greenspan's Basic & Clinical Endocrinology. 9th ed. New York, N.Y.: The McGraw-Hill Companies; 2011. http://accessmedicine.mhmedical.com. Accessed July 25, 2017.
- McCulloch DK. Management of blood glucose in adults with type 1 diabetes mellitus. https://www.uptodate.com/contents/search. Accessed July 25, 2017.
- Drug treatment of diabetes mellitus. Merck Manual Professional Version. https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/diabetes-mellitus-and-disorders-of-carbohydrate-metabolism/drug-treatment-of-diabetes-mellitus. Accessed July 25, 2017.
- O'Neal T, et al. Dawn phenomenon. In: StatPearls. Treasure Island, Fla.: StatPearls Publishing; 2017. https://www.ncbi.nlm.nih.gov/books/NBK430893/. Accessed July 25, 2017.