Tamoxifen often causes changes associated with menopause, however you can still get pregnant while using it. Getting pregnant while taking Tamoxifen may be harmful to the fetus. If you are young and sexually active, it is best to use some type of "barrier" method of birth control (like a condom and/or a diaphragm) while you are taking Tamoxifen. Do not use an oral contraceptive (like the "Pill"), or an injection or an implant that involves hormones, since they may change the effects of your hormone therapy. Your health care provider can answer your specific questions about a contraceptive. Tell your health care provider right away if you think you have become pregnant while taking this medicine.
If you have gone through menopause you may be taking hormone replacement therapy like estrogen and progesterone. This is usually not advised for breast cancer patients, and it is essential that you discuss this with your doctor.
Long term studies of Tamoxifen are still continuing, and health care providers are studying the long term effects. Your doctor will determine the best possible dosage for you.