Prolactin is a pituitary hormone that is involved diverse physiological functions, such as lactation, reproduction, metabolism, osmoregulation, immunoregulation, and behavior. Its level of glycosylation is low in vivo, which favors its expression in bacterial systems. In the present work recombinant human prolactin (rec-hPRL) was expressed from the p1813-hPRL vector in Escherichia coli strain in inclusion bodies with 530.67 mg of rec-hPRL per liter of induced bacterial culture. The solubilization and renaturation of rec-hPRL followed by two methods described in the literature for this protein: one with detergent and basic pH, and other urea and dialyses was done by studying. The protocol with detergent/basic pH was not successful, whereas protocol with urea/dialyses was obtained pure protein and this was optimized. Rec-hPRL was obtained in a soluble, pure and active form, when the sample was 8-fold concentrated in the solubilization phase, allowing 33% recovery, 3-fold more that the original method. The pure protein was obtained with 38.37 i. u./mg activity, which is three times greater than that of the PRL standard from the WHO. In conclusion, this work obtained the highest production of rechPRL, and concentrating the sample eight times in the solubilization stage was decisive for obtaining a highly concentrated, active protein for future work.