Contraception is the use of artificial techniques in preventing pregnancy as a consequence of sexual intercourse by many women around the world. This study was carried out to investigate the biochemical effects of contraception on reproductive hormones in women using contraceptives. One hundred and eighty (180) women using different methods of contraception, were recruited for this study from Ekiti State University teaching hospital, Ado-Ekiti, Ekiti State, Nigeria, having obtained ethical clearance. The subjects were divided into six groups based on the contraceptive method used. Group 1 served as control (women using natural planning method), Group 2 (women using oral pills), Group 3 (women using intra uterine device, IUD), Group 4 (women using implant), Group 5 (women using injection) and Group 6 (women using condoms). Parameters including Body mass index (BMI) and some major reproductive hormones were estimated in the plasma of all the groups, using Enzyme linked immunosorbent Assay (ELISA). The results showed significant increase in the BMI of women using pills, IUD, Implant and Injection (P<0.05). Significant increases were observed in the concentration of Progesterone and Oestrogen in women on injection, IUD and Oral Pill users (P<0.05). However, Significant decrease were observed in the levels of Prolactin, Follicle stimulated hormone and Testosterone in same women using injection, IUD and Oral Pills. Hence, it can be said that reproductive hormones are implicated with the use of contraception, especially in the methods outside the natural and the use of condoms.