Self-reported adherence is usually overestimated. Most people prescribed chronic daily medication take it ~60% of the time, but say/believe they take it 90% of the time.
People with cystic fibrosis are instructed to spend more than an hour a day sitting through up to 7 nebulizer treatments. Daniels et al used a smart nebulizer machine to spy on 78 of their patients. Median self-reported adherence was 80%; actual median adherence was 36%. But could YOU take 7 nebulizer treatments a day? CHEST 2011;140:425-432.