Introduction: Ensuring adequate access to health care is essential for timely delivery of preventive services. It is important to evaluate the prevalence and determinants of difficulty in accessing medical care in the overall U.S. population and among those with high-risk chronic conditions. Methods: The study utilized cross-sectional data from the 2016–2019 Behavioral Risk Factor Surveillance System, a nationally representative telephone-based survey of adults aged ≥18 years. The prevalence and sociodemographic characteristics associated with difficulty in receiving medical care were assessed, including regional variations across U.S. states. Results: The prevalence of difficulty in accessing medical care was 14% overall, 15% among those with hypertension, 15% among those with diabetes mellitus, and 17% among those with atherosclerotic cardiovascular disease. Age 18−34 years, having less than high school education, having annual household income <$75,000, unemployment, and living in a state without Medicaid expansion were all associated with a higher risk of not accessing medical care. The prevalence of difficulty in accessing medical care was 27% among individuals with ≥3 of these sociodemographic characteristics. There was regional variation across the U.S. states in the distribution of difficulty in accessing medical care with a median of 13.6% (IQR=11.3%−15.9%) for the overall population: 16.3% (IQR=14.1%−19.0%) among those living in states without Medicaid expansion versus 12.7% (IQR=10.9%−15.6%) among those living in states with Medicaid expansion (p=0.01). Conclusions: In total, 1 in 7 adults report difficulty in accessing medical care. This prevalence is nearly 1 in 4 adults with ≥3 sociodemographic characteristics related to difficulty in accessing medical care. There are regional variations in the distribution of the difficulty in accessing medical care, especially among individuals living in states that have not undergone Medicaid expansion.