Dawn phenomenon vs. Somogyi effect

Both will result in AM (morning) hyperglycemia.

DAWN: “Think Dawn is Down” => Early morning hypergylcemia without preceding hypogylcemia. Secondary to Growth hormone surge at dawn (normal physiology), increasing insulin requirements and serum glucose levels. Treat: May need to increase dose of night time long acting insulin.

SOMOGYI: “SoMo is So Much insulin” => Nocturnal hypoglycemia (from fasting or excess bedtime insulin) causing rebound hypergylcemia. Surge of counter-regulatory hormones (i.e epinephrine and glucagon) that results in hyperglycemia. Treat: Decreasing rather than increasing night time insulin.

NOTE: Evidence (1,2) exists that discredits the Somogyi hypothesis. In fact if a patient has high AM blood sugars, they likely had high blood sugars overnight.

REFERENCES

1. Schernthaner, G. “Dawn phenomenon and Somogyi effect in IDDM.” Diabetes Care 1989 Apr; 12(4): 245-251.
2. Rybicka M, Krysiak R, Okopień B. The dawn phenomenon and the Somogyi effect – two phenomena of morning hyperglycaemia. Endokrynol Pol. 2011;62(3):276-84.