The Somogyi Effect - Rebound Hyperglycemia

Testing blood sugar
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If there were a diabetes spelling bee, one of the real stumpers would be "Somogyi." At some point in learning about diabetes care you're likely to come across this word in reference to the Somogyi effect, sometimes known as "rebound hyperglycemia."

Named for the Hungarian physician who first described it in 1938, the Somogyi effect occurs when blood sugar (glucose) levels drop too low during the night, causing the body to overcompensate, resulting in a blood sugar spike in the morning.

What Causes the Somogyi Effect?

The Somogyi "rebound" effect is usually triggered either by an excessive dose of insulin at night or neglecting to eat a pre-bedtime snack. Both of these oversights can cause blood sugar to drop too low in the middle of the night, usually without symptoms. In fact, it is possible to sleep right through such an episode of hypoglycemia.

During sleep, the body reacts to the low blood sugar levels by releasing hormones that prompt the liver to release glucose into the bloodstream. These hormones then prevent the glucose from being absorbed and blood sugar levels stay high.

Morning hormones also drive higher levels of glucose -- this is known as the dawn phenomenon. Within a very short period of time, the body has gone from hypoglycemia to hyperglycemia -- all while sleeping. Note that most morning hyperglycemia is the result of overnight hypoinsulinemia (abnormally low insulin) and most people will therefore need additional insulin.

The Somogyi effect is not without controversy. Research finds that it is rarer than it is generally thought to be, and there is dispute about what its causes may be. Low fasting blood glucose happens more often after silent nocturnal hypoglycemia, according to a paper published in 2013. The cases where the blood sugar level was high after a nocturnal hypoglycemia episode happened after the episode was treated by administering glucose.

How is the Somogyi Effect Diagnosed?

When someone with diabetes is waking up with high blood sugar levels in the morning, a healthcare provider may recommend testing blood glucose levels in the middle of the night, most likely between 2 a.m. and 3 a.m. If blood sugar levels are low at that time but high in the morning, the patient is probably experiencing the Somogyi effect.

If the blood sugar levels are high at around 2 to 3 a.m., this would mean that the patient would require more insulin during the night. This can be achieved by changing the dosing schedule or increasing the dosage of insulin.)

How is the Somogyi Effect Prevented and Treated?

A doctor or healthcare provider will probably recommend changes in insulin dosage or bedtime snacking to prevent blood sugar levels from dropping too low in the middle of the night. With proper treatment, morning blood sugar levels will improve.


Dinsmoor, Robert. "Somogyi Effect." 15 Aug. 2006. Diabetes Self-Management.

Bolli GB, Perriello G, Fanelli CG, De Feo P. Nocturnal blood glucose control in type I diabetes mellitus. Diabetes Care. 1993 Dec;16 Suppl 3:71-89.

Choudhary P, Davies C, Emery CJ, Heller SR. "Do high fasting glucose levels suggest nocturnal hypoglycaemia? The Somogyi effect-more fiction than fact?" Diabet Med. 2013 Aug;30(8):914-7. doi: 10.1111/dme.12175. Epub 2013 May 15.