What Causes High Blood Sugar Levels in the
There are two reasons why your blood sugars levels may be high
in the morning – the dawn phenomenon and the Somogyi effect.
Dawn phenomenon. The dawn phenomenon
is the end result of a combination of natural body changes that occur during the
sleep cycle and can be explained as follows. Your body has little need for
insulin between about midnight and about 3:00 a.m. (a time when your body is
sleeping most soundly). Any insulin taken in the evening causes blood sugar
levels to drop sharply during this time. Then, between 3:00 a.m. and 8:00 a.m.,
your body starts churning out stored glucose (sugar) to prepare for the upcoming
day as well as releases hormones that reduce the body’s sensitivity to
insulin. All of these events happen as your bedtime insulin dose is also wearing
off. These events, taken together, cause your body’s blood sugar levels to
rise in the morning (at "dawn").
Somogyi effect. A second cause of
high blood sugar levels in the morning might be due to the Somogyi effect (named
after the doctor who first wrote about it). This condition is also called
"rebound hyperglycemia." Although the cascade of events and end result
– high blood sugar levels in the morning – is the same as in the dawn
phenomenon, the cause is more "man-made" (a result of poor
diabetes management) in the Somogyi effect. There are two potential causes. In
one scenario, your blood sugar may drop too low in the middle of the night and
then your body releases hormones to raise the sugar levels. This could happen if
you took too much insulin earlier or if you did not have enough of a bedtime
snack. The other scenario is when your dose of long-acting insulin at bedtime is
not enough and you wake up with a high morning blood sugar.
Because the cascade of events is the same with both scenarios,
how is it determined if the dawn phenomenon or Somogyi effect is causing the
high blood sugar levels?
Your doctor will likely ask you to check your blood
sugar levels between 2:00 a.m. and 3:00 a.m. for several nights in a row. If
your blood sugar is consistently low during this time, the Somogyi effect is
suspected. If the blood sugar is normal or high during this time period, the
dawn phenomenon is more likely to be the cause.
How can this situation be corrected?
Once you and your doctor determine how your blood
sugar levels are behaving at night, he or she can advise you about the changes
you need to make to better control them. Options that your doctor may discuss
- Changing the time you take the long-acting insulin in
the evening so that its peak action occurs when your blood sugars start
- Changing the type of insulin you take in the evening
- Taking extra insulin overnight
- Eating a lighter breakfast
- Increasing your morning dose of insulin
- Switching to an insulin pump, which can be programmed
to release additional insulin in the morning
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