- Females of childbearing potential (FCBP)† must have a negative serum or urine pregnancy test with a sensitivity of at least 25 mIU/mL not more than 3 days from the start of study drug and must either commit to continued abstinence from heterosexual intercourse or begin one acceptable method of birth control, at least 4 weeks before she starts taking lenalidomide. FCBP must also agree to monthly pregnancy testing and must be counseled at a minimum of every 4 weeks about pregnancy precautions and risks of fetal exposure.