Tamoxifen side effects and your experiences
Hello I am Vanessa. I am 47 no menopause. I was diagnosed with LCIS in December (11 mm) + atypical ductal & lobular hyperplasia. Had my surgery in January 2025. No quimio nor radio therapy was needed.
Just tamoxifen (20 mg). It has been a roller coaster in several ways. I had to take of mirena, change medication like sertraline for other one and started tamoxifen.
I have been feeling some hot flashes and dizziness at the begginig but the worst for me has been being so tired or exhausted all day. I do not have energy, not happiness and smiles as before. I cannot concentrate well at work too... to much tired. I also feel pain in my back and have a lot of bruisers if I hit something.
I am talking always with my mental health support specialist but I wanted to know your experiences and any possible tip to increase my energy.
I feel like a complete different person.…I was really energetic and sporty and smile person and now I am always really sleepy and tired.
Thanks a lot and take care.
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Hi @vaneira, and welcome to Breastcancer.org! We’re really glad you found us.
If you haven’t already, you might find helpful info and tips on our main site, especially in the Hormonal Therapy section. We also have an article that might help with what you’re feeling:
Hope this helps. We're here for you, and we hope the community brings you connection, support, and understanding. We're looking forward to hearing more from you soon!
Sincerely,
The Mods
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I hear you! I’m at year 4 on Tamoxifen and the worst side effect has been the change of my personality and cognitive sluggishness! I used to be a voracious reader but now can’t remember what I’ve read from chapter to chapter without detailed notes. I used to be zesty, but now I’m dull. I don’t ever get as happy and exhilarated as I used to, but I also don’t experience the level of sadness, either. It’s like I have a wet blanket over my emotions. I know it’s tamoxifen because I had to take a few weeks off for a major surgery and I started feeling again. The fatigue is major, too. You could try a short acting stimulant if it’s giving you trouble at work, but I just increased my coffee. Even though you’re tired, adding MORE exercise will help after a few weeks! Yoga can really be helpful for wellbeing. What’s gotten me through is knowing these side effects are not as bad as some of the therapies for advanced cancer, and I’d rather take one pill a day than a mess of pills, infusions, shots, etc. Take it a month at a time, you can do it!
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Hi,
I started taking 20g of tamoxifen in August 2025. I had severe dizziness, fatigue and insomnia. I did some research and found out that I could take a lower dose at 10mg. Asked my oncologist for a lower dosage. Took the lower dose and had some improvement with the side effects, but now I’m still feeling fatigue all the time. My oncologist recommended I could take a break from taking the medication then re-start when I feel better. I haven’t stopped taking it yet but I might consider this option because I’m barely functioning with the fatigue at work and home with an 8year old plus after school activities.
Talk to your oncologist about taking a lower dose at 10mg.
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