BACKGROUND: Patient knowledge regarding why they are prescribed their medications is paramount for the delivery of quality and patient-centered cardiometabolic care. OBJECTIVE: To generate national estimates of the proportion of patients who do not know why they are taking their anti-hypertensive, anti-diabetes, or anti-lipid medications. DESIGN: Cross-sectional study using data from the National Health and Nutrition Examination Survey from January 2013 through March 2020. PARTICIPANTS: Non-institutionalized adults in the United States. MAIN MEASURES: Medication use was ascertained by respondent self-report and pill bottle review of their anti-hypertensive, anti-diabetes, or anti-lipid medications. The primary outcome was the proportion of respondents with a knowledge deficiency about why they were taking their respective medications defined by respondents reporting (1) they did not know why or (2) an incorrect indication for why they were taking each medication. We also report knowledge deficiency prevalences stratified by respondent characteristics and use multivariable logistic regression analysis to assess for relationship between respondent characteristics and odds of having a knowledge deficiency. KEY RESULTS: 4.9% (95% confidence interval [CI] 4.0-5.6%, n=391) of respondents on cardiometabolic medications had ≥ 1 knowledge deficiency, which corresponds to approximately 3,152,243 US adults. This was driven most strongly by knowledge deficiencies in anti-hypertensive medication use (4.5%, 95% CI 3.7-5.3%). There were large variations in knowledge deficiency prevalence by respondent characteristics. Most notably, 12.9% (95% CI 9.8-16.0%) of adults ≥ 80 years and 12.2% (95% CI 8.6-16.0%) of adults taking ≥ 10 medication had a knowledge deficiency. Of older adults with polypharmacy (≥ 5 prescriptions), 11.2% (95% CI 8.9-13.5%) >
65 years and 15.8% (95% CI 11.5-20.2%) >
80 years had a knowledge deficiency. CONCLUSIONS: Most adults report a plausible reason for their use of their cardiometabolic medications. However, the prevalence of having a knowledge deficiency varied greatly by respondent demographic and health characteristics.