Full coverage policies for medicines have been implemented worldwide to alleviate medicine cost burden and promote access to medicines. However, few studies have explored the factors associated with free medicine use in patients with chronic diseases. This study aimed to analyze the utilization of free medicines by patients with hypertension and diabetes after the implementation of the full coverage policy for essential medicines (FCPEM) in Taizhou, China, and to explore the factors associated with free medicine use. We conducted a descriptive analysis of characteristics of patients with and without free medicine use and performed a panel logit model to examine factors associated with free medicine use, based on an electronic health record database in Taizhou from the baseline year (12 months in priori) to three years after FCPEM implementation. After FCPEM implementation, the proportion of patients without any free medicine use decreased from 31.1% in the baseline year to 28.9% in the third year, while that of patients taking free medicines rose from 11.0% to 22.8%. Patients with lower income or education level, those with agricultural hukou, patients aged 65 and above, married patients, and patients in the Huangyan district were more likely to take free medicines. In conclusion, FCPEM contributed to improved medicine access, especially in vulnerable populations. Local policy makers should consider expanding the coverage of FCPEM to other types of medicines and cultivate the potential of social supports for patients to enhance the effectiveness of FCPEM policies.