You can gain weight but you can also lose weight. There's no physiological reason one would gain weight. Many women begin tamoxifen right on the heels of finishing chemo. Weight gain vcan be a result of steroids, inactivity due to fatigue, early onset menopausal symptoms from chemo but there's no way to know what's actually causing it. Your best bet is to eat right and get active. As active as you are up to :)

I heard that if you are not experiencing side effects it is not working. Two tomorrow for me and just headaches. I don't want to experience side effects but I also want to know if it is working.

I did a bunch of research on this topic and have decided to demand that I have this test done. The Mayo Clinic are big proponents of getting the test due to their own study results. I don't see the harm of finding out how my CYP2D6 enzyme metabolizes. Also, most studies focused on post menopausal women, so as a premenopausal woman I just don't think those studies hold as much weight and I can't wait until they come to some definitive conclusions. If my enzyme doesn't metabolize correctly, I want to know so that I can seriously then consider the option of ovarian suppression and going on an AI.

My oncologist said they no longer use the test. Conflicting research studies. I am going for a second opinion. There has to be reasons why some people have such bad side effects. I have heard the drug is cumulative and side effects may happen down the road but so far for me it has been 2 months and I am just tired with mild aches. So of course I am still wondering if the drug is working. I take glucosamine so my onc thinks that helps with joint pain. I also exercise on a recumbent bike treadmill and elliptical 4 times a week

My oncologist said you could experience weight gain. Did any of you gain weight? I start tamoxifen in about 4 weeks. I really don't want to gain weight! That's all I need on top of all the other flattering effects of BC.