Background. Many of our daily behaviors are habitual, occurring automatically in response to learned contextual cues, and with minimal need for cognitive and self-regulatory resources. Behavioral habit strength predicts adherence to actions, including to medications. The time of day (morning vs. evening) may influence adherence and habit strength to the degree that stability of contexts/routines varies throughout the day.

Purpose. The current study evaluates whether patients are more adherent to morning versus evening doses of medication and if morning doses show evidence of greater habit strength than evening doses.

Methods. Objective adherence data (exact timing of pill dosing) were collected in an observational study by electronic monitoring pill bottles in a sample of patients on twice-daily pills for Type 2 diabetes (N = 51) over the course of 1 month.

Results. Data supported the hypothesis that patients would miss fewer morning than evening pills. However, counter to the hypothesis, variability in dose timing (an indicator of habit strength) was not significantly different for morning versus evening pills.

Conclusions. Findings suggest that medication adherence may be greater in the morning than in the evening. However, more research is needed to evaluate the role of habitual action in this greater adherence. Furthermore, future research should evaluate the validity of behavioral timing consistency as an indicator of habit strength.