- Serum potassium within the normal range 11. Patients must be registered into the mandatory REVLIMID REMS™ program, and be willing and able to comply with the requirements of the REVLIMID REMS™ program 12. FCBP† must have a negative serum or urine pregnancy test with a sensitivity of at least 25 mIU/mL within 10 - 14 days prior to and again within 24 hours of starting ruxolitinib and must either commit to continued abstinence from heterosexual intercourse or use acceptable methods of birth control, one highly effective method and one additional effective method AT THE SAME TIME, and at least 28 days before she starts taking ruxolitinib with or without lenalidomide. FCBP must also agree to ongoing pregnancy testing. Men must agree to use a latex condom during sexual contact with a FCBP even if they have had a vasectomy. All subjects must be counseled at a minimum of every 28 days about pregnancy precautions and risks of fetal exposure.