The time of effectiveness varies widely between testosterone boosters. You will feel the short-term effects of some supplements kick into effect within 30 to 60 minutes, for example. Other testosterone boosters may need to be taken daily for 30 to 60 days before long-term effects (like fat loss, increased lean body mass, and higher testosterone levels) are noticed. Generally, most people report significant improvements within the first 4 to 12 weeks of taking testosterone booster supplements.