Each vial contains 250mg per 1ml of testosterone undecanoate, it is used by athletes and bodybuilders in the UK as well as for andropause by men with low testosterone. Low testosterone levels in men is a real problem that can be debilitating in many ways. This articles explains the various signs that are often attributed to low T, and how Nebido can help men. When boys go through puberty, testosterone is what helps boys develop male features like a deeper voice, body and facial hair, and muscle strength. Testosterone is needed for men to make sperm. As men age beyond 30 testosterone levels generally decrease, so older men tend to have low blood testosterone levels.