The dawn phenomenon, also called the dawn effect, is the term used to describe an abnormal early-morning increase in blood sugar (glucose) — usually between 2 a.m. and 8 a.m. — in people with diabetes.
Yes, the dawn phenomenon will affect your HRV. We believe if you take your HRV at the same time every morning, the noise from this phenomenon will be reduced, as you should in theory be at the same point within the dawn phenomenon when you take readings.
The goal with the Morning Readiness readings is to get a baseline established on which day-to-day changes can be assessed. No matter what time of day, something will be acutely affecting your HRV, so the goal is to be as consistent as possible so that the effect becomes a regular part of the baseline, and changes can be evaluated from there.
As an example, if you wait until 10 am to take your readings, chances are you may have seen the news or checked your email, which will in their way affect your HRV.