dawn phenomenon

[dôn]
n.
  1. The occurrence of abrupt increases in fasting levels of plasma glucose concentrations between the hours of 5 and 9 a.m., without preceding hypoglycemia, especially in diabetic patients receiving insulin therapy.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.