However, tamoxifen was life threatening for some breast cancer patients who developed uterine cancer while taking tamoxifen. Women who are taking tamoxifen should talk with their doctor about having regular pelvic examinations, and should also be checked promptly if they have any abnormal vaginal bleeding between scheduled exams. The total number of women who have experienced this side effect is small. The risk of having a blood clot due to tamoxifen is similar to the risk of a blood clot when taking estrogen replacement therapy. Women in the BCPT who took tamoxifen also had an increased chance of developing blood clots and an increased chance of stroke.
Women taking tamoxifen appear to be at increased risk for developing cataracts.
Other eye problems, such as corneal scarring or retinal changes, have been reported in a few patients. Although tamoxifen can cause liver cancer in particular strains of rats, it is not known to cause liver cancer in humans. It is clear, however, that tamoxifen can sometimes cause other liver toxicities in patients, which can be severe or life threatening. Doctors may order blood tests from time to time to check liver function. One study suggested a possible increase in cancers of the digestive tract among women receiving tamoxifen for breast cancer.