Actemra stays in your system for a very long time, up to 3.5 months or 107 days. This is calculated by using the half-life of Actemra (also called the t1/2), which is the time it takes for 50% of a medicine to leave the body. The t1/2 for Actemra is 21.5 days. Experts have determined that it takes 4 to 5 half-lives for a medicine to be completely eliminated by the body, which works out to be 86 to 107 days (2.9 to 3.5 months) for Actemra.