Background:The selection of blood donor candidates contributes to the safety of donors and donor recipients. An understanding of the characteristics, demographic characteristics, and types of potential blood donors are essential to obtain an accurate picture of the donor donors, thereby guiding recruitment strategies and providing benchmarks to assess the success of blood donation. Objective: This scientific work aims to analyze the deferred blood donor candidates annually based on the required blood donor characteristics at the Blood Transfusion Unit (BTU) of Dr. Sardjito Hospital, Yogyakarta, Indonesia, from 2017 to 2019. Method: This observational analytic study applied a retrospective design and was conducted at Dr. Sardjito Hospital, Yogyakarta. The data were collected from the donor registration information system and database in the blood request system for the 2017-2019 period. The statistical analysis was conducted using the Chi-Square test in the SPSS version 22. Results: The deferred blood donor candidates in 2017-2019 amounted to 618 (0.82%) out of 75,067 total blood donors, most of whom were female, reaching an annual percentage of 50.7% in 2017, 50.9% in 2018, and 59.1% in 2019. The age range of both male and female deferred blood donor candidates was 17-30 years. The Hb levels of < 12.5 g/dL were mostly found in female blood donors, reaching a peak of 82.4% in 2017, 83.9% in 2018, and 85.4.6% in 2019. Voluntary blood donors accounted for 94.7% (in 2017), 98.6% (in 2018), and 100% (in 2019) of the female deferred blood donor candidates. All analytical tests resulted in a p-value of < 0.0001. Most of the deferred blood donor candidates had blood type O with a p = 0.026. The most common cause of deferral was high or low Hb levels in female blood donors with an age range of 17-30 years. Conclusions: The deferred blood donor candidates in 2017-2019 amounted to 618 (0.82%) out of 75,067 total blood donors, most of whom were female with the most common deferral reason of Hb levels < 12.5 g/dL in the age range of 17-30 years.