Nolvadex (tamoxifen) is a prescription medicine used to reduce the risk of developing breast cancer in women from the risk group (because of age or medical history), as well as those diagnosed with ductal carcinoma is situ and who have had a surgery or radiation treatment for that. Some health condition you had in the past can make your treatment less efficient or actually be the reason for developing serious side effects. Mention to your health care provider the fact of ever being diagnosed with high blood pressure, diabetes, or if you ever had a blood clot in the lungs, a heart attack or a stroke. People who smoke regularly are also at risk of developing some dangerous side effects as cancer of the uterus, blood clots in the lungs and a stroke. Make sure you show up for the regular appointments at your doctor's and before having any lab test done make sure the personnel knows you are taking Nolvadex for the results to be accurate.