Methods and pharmaceutical compositions for reliable achievement of acceptable serum testosterone levels

The present invention relates to pharmaceutical compositions, formulated for injectable administration, which comprises a testosterone ester, in particularly testosterone undecanoate, in a vehicle comprising castor oil and a co-solvent. Upon injecting the compositions according to a particular administration scheme, reliable levels of testosterone in serum in the normal physiological range is achieved for a long period. This allows for the use of the compositions in hormone replacement therapy and male contraception without concomitant monitoring of testosterone levels in serum by a physician.