Somogyi effect
Also called Somogyi phenomenon, rebound hyperglycemia.
The Somogyi effect is the idea, first reported by Michael Somogyi, that a low during the night leads to a high fasting glucose the next morning. CGM studies since then have found it rare or absent; in one CGM study of people with type 2 diabetes, fasting glucose was lower after nights with a low, not higher. A fasting high is usually put down to either the dawn phenomenon or the Somogyi effect, and the two are treated in opposite ways. (Huang et al., Somogyi effect study, 2022)
Worked example
The pattern the theory describes: 55 mg/dL (3.1 mmol/L) at 3 a.m., then 210 mg/dL (11.7 mmol/L) at 7 a.m. A CGM shows the whole night, so the low either is on the graph or is not.
Related terms
Sources, quoted
- Huang et al., Somogyi effect study, 2022: “It was first reported by Michael Somogyi in 1959 that nocturnal hypoglycemia may lead to fasting hyperglycemia the next morning, which is known as the “Somogyi effect””
- Huang et al., Somogyi effect study, 2022: “With the advent of continuous glucose monitoring systems (CGMs), the Somogyi effect proved to be rare or absent in most studies in the following decades”
- Huang et al., Somogyi effect study, 2022: “Therefore, the dawn phenomenon and Somogyi effect should be treated in an opposite manner.”
- Huang et al., Somogyi effect study, 2022: “Confirmation of the Absence of Somogyi Effect in Patients with Type 2 Diabetes by Retrospective Continuous Glucose Monitoring Systems”
- Huang et al., Somogyi effect study, 2022: “Morning fasting glucose was observed lower after nights with nocturnal hypoglycemia compared with nights without hypoglycemia”
Every quote above is checked against its source page before each update of this site; last checked 2026-10-06. The worked example is our own arithmetic. This page explains a term; it is not advice for a person's treatment.