I read a study about vitamin D reducing the side effects of the drug Arimidex (anastrozole) and asked my oncologist if he would approve me taking this daily. I am taking the anti-cancer drug Arimidex (aromatase inhibitor) daily and must do so for the next 5 years due to estrogen-positive breast cancer. When I had my most recent appointment, my oncologist was very pleased that I am finding the Arimidex / anastrozole side effects manageable, and he said that taking this product (5000 IUs of Vitamin D3 daily) may be one of the reasons for that. There are several women in my breast cancer support group who have had to discontinue taking Arimidex due to side effects, and I am hoping that this product will help to prevent that happening to me. So far so good (65 days). I am pleased with the characteristics of this product (e.g., made in USA, does not contain soy or gluten) and I am so glad that I found it. Please do not take this review as offering medical advice--everyone needs to consult with one's own doctor to see if it is acceptable to take any supplements!! I did not start taking this product until AFTER I got my doctor's permission because everyone's case is different. I am just presenting my own experiences as a starting point because it may help someone else. After purchasing the first bottle I was able to obtain a second, free bottle, but that was not dependent on writing a positive review or even on writing a review at all. I had terrible side effects from previous Chemotherapy and so I was worried that I would not be able to tolerate the daily pill for five years due to side effects, but I am tolerating it well and I believe this product is helping. If you think this might help you, google Vitamin D and Arimidex side effects, and also check with your doctor before taking it. Good luck to anyone who might be in a similar situation to mine and I hope this information is helpful to you