Lots of people say they're taking their drugs correctly when they're really skipping doses. Some people lie to avoid an argument, others just don't remember.
That's why researchers at the University of Washington asked patients how regularly they were taking their medications -- then they tested each patient's blood levels to see if they were telling the truth.
As reported in the Journal of Clinical Epidemiology, the accuracy of the answers varied by drug:
- For patients taking aspirin, which is used to prevent blood clotting and reduce the risk of heart attacks and stroke, the answers matched up with blood levels only 16 percent of the time.
- Patients taking propranolol, which is used to reduce blood pressure, gave answers that matched the blood tests 43 percent of the time.
- Hydrochlorothiazide, another blood-pressure drug, did a little better. The answers patients gave matched the blood level reports 63 percent of the time.
- The big winner was digoxin, which is used to strengthen the heart. The agreement between patient reports and blood levels was 94 percent.