ORTHO TRI-CYCLEN LO (norgestimate/ethinyl estradiol) is a "triphasic" birth control pill. A triphasic birth control pill delivers a constant level of estrogen and three different levels of progestin throughout your cycle. Phasing the progestin over the course of your cycle helps ensure that you receive the minimal amount of hormone needed to prevent you from getting pregnant. While both ORTHO TRI-CYCLEN LO and ORTHO TRI-CYCLEN deliver low levels of progestin over the course of your cycle, ORTHO TRI-CYCLEN LO delivers a lower amount of estrogen-25 mcg compared to 35 mcg. This low level of estrogen was developed to help minimize the occurrence of nuisance side effects, such as breakthrough bleeding and spotting.* Birth control pills with lower levels of estrogen can be associated with higher rates of these side effects than Pill formulations containing slightly more estrogen. The unique combination of hormones-three levels of progestin and a lower level of estrogen-in ORTHO TRI-CYCLEN LO helps strike the right balance of efficacy and tolerability.