Table 1

Six levels of drug adherence

Drug adherence levelAnswers selected by the patient (best applied to drug intake)
1. High drug adherenceNo drug holidays, no missing doses and no schedule errors
2. Good drug adherenceNo drug holidays and no missing doses; schedule errors ≥4 h
3. Moderate drug adherenceNo drug holidays; missing doses once or twice a month and/or schedule errors ≥12 h
4. Poor drug adherenceDrug holidays for 2–3 days and/or missing doses ≥1/week
5. Very poor drug adherenceSystematically skipping a daily dose and/or drug holidays ≥6 days
6. DiscontinuationDrug discontinuation