The dawn phenomenon and the Somogyi effect
cause high blood sugar levels, especially in the morning before breakfast, in
The dawn phenomenon occurs
Hormones (growth hormone,
cortisol, and catecholamines) produced by the body
cause the liver to release large amounts of sugar (glucose) into the
bloodstream. These hormones are released in the early morning hours. These
hormones also may partially block the effect of
insulin, whether it's insulin your body produces or
insulin from the last injection.
If the body doesn't produce enough
insulin (which occurs in people with
type 1 diabetes and a few people with
type 2 diabetes), blood sugar levels may rise. This
may cause high blood sugar in the morning before the person eats.
The Somogyi effect can occur when
a person takes long-acting insulin for diabetes. 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
A person's body responds to the low blood sugar in the same
way as in the dawn phenomenon, by causing a high blood sugar level in the early
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 around 2 a.m. to 3 a.m.
for several nights.
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.