Rapamycin, an FDA approved drug that inhibits the mTOR pathway, is known to prolong lifespan in yeast, invertebrates, and vertebrates. In aged mice, reports of lifespan extension had been demonstrated using continuous treatment. More recently, our lab showed that a shorter three-month transient treatment of rapamycin sufficiently extends lifespan. However, some questions remain. Is there an optimal rapamycin dosage and treatment length that results in a robust effect on healthspan and lifespan? We had noted a sex-specific increase in cancer incidence and no lifespan extension in females that received daily intraperitoneal (IP) injections of rapamycin, the same regimen that robustly extended lifespan in male mice. Currently, we are testing the effects of daily, once weekly, and twice weekly rapamycin injections in female mice. We have already uncovered an increased incidence of eye inflammation in the animals that received daily drug treatment compared to all the other cohorts. Interestingly, this increase in eye inflammation also occurred in mice that were fed high-dose rapamycin. These data suggest that high dosages present unwanted side effects in female mice and it is crucial to find an optimal treatment regimen to minimize the undesirable effects of rapamycin. Additional assays to measure physiological parameters such as body fat mass, body temperature, muscle function, cognitive function, and lifespan will be done in our study. We hope to reveal the proper drug dose and intervention frequency that provides the best outcome, enhancing longevity while minimizing or even abolishing the detrimental outcomes associated with rapamycin.