The dawn phenomenon and the Somogyi effect
cause high blood sugar levels, especially in the morning before breakfast, in
people who have
The dawn phenomenon is a normal rise in blood sugar as a person's body prepares to wake up.
In the early morning hours, hormones (growth hormone,
cortisol, and catecholamines) cause the liver to release large amounts of sugar into the
bloodstream. For most people, the body produces insulin to control the rise in blood sugar.
If the body doesn't produce enough
insulin, blood sugar levels can rise. This
may cause high blood sugar in the morning (before eating).
If the blood sugar level drops
too low in the early morning hours, hormones (such as growth hormone, cortisol,
and catecholamines) are released. These help reverse the low blood sugar level
but may lead to blood sugar levels that are higher than normal in the morning.
An example of the Somogyi effect is:
A person who takes insulin doesn't eat a
regular bedtime snack, and the person's blood sugar level drops during the
The person's body responds to the low blood sugar by releasing hormones that raise the blood sugar level. This may cause a high blood sugar level in the early morning.
How can you tell the difference?
effect can occur any time you or your child has extra insulin in the body. To
sort out whether an early morning high blood sugar level is caused by the dawn
phenomenon or Somogyi effect, check blood sugar levels at bedtime, around 2 a.m. to 3 a.m., and at your normal wake-up time
for several nights. A continuous glucose monitor could also be used throughout the night.
If the blood sugar level is low at 2 a.m. to
3 a.m., suspect the Somogyi effect.
If the blood sugar level is
normal or high at 2 a.m. to 3 a.m., it's likely the dawn phenomenon.
Primary Medical Reviewer
John Pope, MD - Pediatrics
Specialist Medical Reviewer
Stephen LaFranchi, MD - Pediatrics, Pediatric Endocrinology
How this information was developed to help you make better health decisions.