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Fatigue- Tamoxifen?

I have pretty decent energy until around 3 every afternoon. Meaningful interactions with people after 7 pm seems impossible. I'm skipping social activities scheduled in the evening because of it. Copious amounts of strong coffee helps some, but then I wake up all night. To me, checking out of humanity at 6 is better than insomnia.

My husband suggested the time change is still effecting me, but I wonder if it's the Tamoxifen, or irrationally, some hidden cancer somewhere. Am I supposed to report this fatigue to my MO (I have a follow up in Jan)? I am exercising and eating healthfully. Is there anything else I can do to lessen the fatigue?

Edited to add, I am in general less energetic now, but it isn’t as much of a problem as the late afternoon and evening fatigue.


  • salamandra
    salamandra Member Posts: 735

    This is what happened for me with tamoxifen. I would feel fine in the mornings - bicycle many miles a day for my commute to work or radiation - and then conk out by 4pm. I worked with the hospital psychiatrist to try various stimulants, but even the drug they use for narcolepsy couldn't give me those hours back. I never napped before in my life. It was literally impossible for me to earn a living and have a life with the amount of waking hours tamoxifen left me with.

    I ended up trying many different generic brands, half doses, splitting doses, etc, but none of it made a difference. The one thing I didn't try was to see whether the liquid version of the drug would either not have that side effect for me or if I'd be able to go down to a low enough dose with it to help, although that low the efficacy might be impacted anyway. I spent about 9 months trying to find a way to stay on tamoxifen without being sedated.

    From these boards, I learned about Fareston, which is the SERM after tamoxifen that has the next best amount of research for prevention of recurrence. Based on my own research, I felt there was enough evidence to support me taking it even though it's only FDA approved for treatment of advanced cancer and not recurrence prevention. (It is approved for recurrence prevention in other countries). After a few conversations with my doctor and she did her own research, she agreed and prescribed it for me and luckily my insurance covered it. It is much more expensive than tamoxifen.

    Thank goodness it did not have the sedating side effect for me. If it had, I would have had to decide whether to try OS/AI or to take my chances without any endocrine treatment.

    Based on my own experience, I wish I had spent less time wrestling with the tamoxifen. It made for a very very difficult year. On the other hand, it's possible that my insurance would not have covered it without the paper trail of the brands that I tried so maybe it was worth it in the end. You should definitely speak with your doc and don't sugar coat it or put on a brave face, as women are often trained to do. My doctor took it a lot more seriously when I emphasized the impact on my ability to work and earn an income.

    My impression is that many doctors don't take this kind of side effect seriously enough, and may try to direct you to things like acupuncture or diet or things that are not really evidence supported but take the work off the doctor's plate. What finally gave me the courage of my convictions was that one thing my doc advised me was to try to take a break from tamoxifen (maybe 1 month? I don't recall) and then build back up by splitting my pills and taking a 10mg dose every other day. At that point, I was able to so clearly see the difference without the tamoxifen and the impact of adding even such a relatively low dose.

    All that said - I think that there are alternate histories where the stimulants might have worked, or where my body may have adapted with time, or a different generic would not sedate me. So I wouldn't necessarily rush to skip those steps. But I just want to say that if you think it's the tamoxifen, it really could be the tamoxifen, and that there IS an alternative that doesn't require shutting down ovaries.

  • waves2stars
    waves2stars Member Posts: 98

    This is so reassuring to me! I wasn’t sure it was a side effect because I take it at night, so thought I should be more tired in the morning than afternoons. Your comment about never napping is the same for me. I would like to have been able to sleep during the day in the last 20 years, but that only happened when I had the flu, lol! I was looking at a career that would require me to be “on” in the afternoons and evenings, but I second guessed my ability to perform based on how I feel now. It feels kind of wrong to say med side effects play a part in career decisions, especially since I was just stage 1. I will definitely contact my MO about trying some different tactics. Thank you

  • pi-xi
    pi-xi Member Posts: 177


    I took my tamoxifen with dinner, ate predominantly plant-based meals, exercised daily and I was exhausted for five years. Worse was the inability to feel joy. I've already been off for four weeks. Time flies! I noticed a big difference rapidly, but then had surgery for a different cancer followed by a colonoscopy, so just recovering now. Cognitively, though, it is a huge relief!

    All this to say that it could definitely be the tamoxifen.

    Hope you find a solution.


  • rah2464
    rah2464 Member Posts: 1,192

    Waves2Stars you exactly describing my existence. I typically have to have a nap (15 min to an hour) daily and I am ready for bed at 6:30 pm. It is all I can do to push to 7 pm Coffee doesn't break the fatigue enough. What does help I find is a single 4-6 hr strength sudafed. I have a lot of allergies anyway but this can keep me somewhat productive on limited days where i really need it. I just recently did a two week "vacation" over Thanksgiving and by the end of the 2nd week I had two full days of my old self and it was wonderful. The restart hasn't been so great but I have noticed carefully how I am reacting. I could literally feel the depressive "fog" laying in after about 3 days restarting the meds. Truly powerful effect on me personally. I am going to speak with my MO about Fareston (thanks, Salamandra) I need to make a change because I want to complete my five years somehow. Thank you Waves for so eloquently stating your experience.

  • beaverntx
    beaverntx Member Posts: 2,962

    Rah, after my recent break from Tamoxifen, I started back on at 20 mg every other day (wanted to use up the supply I had) with my prescriber's blessing. I think she realized I was seriously considering stopping altogether as this was my second break in 3 years. It has been a month, I am noticing some side effects but at a much more tolerable level(at least so far). Now have hope I can make it to 5 years!

  • waves2stars
    waves2stars Member Posts: 98

    Pi-Xi, I am thankful not to have a dulling of my emotions with Tam. I had that while taking Zoloft and the birth control pill. It was distressing looking at people enjoying themselves and wondering if numbing depression was worth numbing happiness, too. I’m so sorry you felt like that for so long, especially considering your BC journey! I am very, very glad to hear you are getting back to your full self even after being on Tam for the whole duration. Congrats on getting through your five year stint

    Rah2464, I am getting Sudafed tomorrow to give it a go! I do have allergies, and cedar is kicking up, so why not see if it helps my evenings??? Again, it is so so comforting to find out quitting or taking a med holiday can reverse this particular side effect!!! I have been concerned this might be permanent.

  • loverofjesus
    loverofjesus Member Posts: 174

    ok I thought I was crazy until I found this thread!! I have been on tamoxifen for 2 months. And I feel like I need a nap every day. Ugh. Would it be better to take it in the evening? The. Maybe I could sleep at night and sleep it off so to speak.

    Any advice???

  • veeder14
    veeder14 Member Posts: 269

    I’ve been onTamoxifen almost 3 years and it keeps me from sleeping well. Never had that problem before. That’s why I need a nap on most days. It doesn’t seem to matter when I take it it keeps me awake.

    You could try taking it at a different time and see what happens. It’s very hard to be tired all the time

  • salamandra
    salamandra Member Posts: 735

    Hi Loverofjesus,

    I had that same side effect from tamoxifen. I needed about 12-15 hours of sleep per day, and I couldn't fit my life around it.

    I tried taking it at night, lower doses, counteracting stimulants, and a lot of different generics, but in the end that side effect persisted. I'm not sorry I tried those things but I'm really glad that I ended up on toremifene, which is another SERM (same class of drugs as tamoxifen). It's not FDA approved in the USA for prevention of recurrence for premenopausal women (it's used for advance cancer) but it's used for that purpose in many other countries and there's at least as much evidence supporting that use as there is supporting any AI drug in premenopausal women (I did a lot of research, and then my doc did her own research, and then we both hoped that insurance would cover it for me, and then it did).

    So... there's stuff you could try and it might work better for you than for me (dose at night, split into 10mg morning and 10mg night, go down to 10mg per day, try different generic brands in case it's an issue with the inactive ingredients, etc). But also know there's a whole other SERM that hopefully your oncologist will support you with.

  • dvcmom3
    dvcmom3 Member Posts: 13

    I am tired all the time ... Nobody understands it .. Have been on Tamox for almost 3 years now and since there was another growth they may want to increase the 5 years to more years on this medication . I am currently battling horrible anxiety and panic attacks . So bad it was affecting me at work . They started me on Zoloft which is working for now .. I am also on muscle relaxers because of the pains in my legs went to three different doctors for relief and nothing was wrong its from the Tamox . Sleep sometimes is good but most of the time it is not . I thought I was crazy as well until I spoke to other Tamox users and many have the same symptoms . You are not alone !!

  • rah2464
    rah2464 Member Posts: 1,192

    DVCmom3 yeah the fatigue can be killer on this drug. Couple things I do that are working for me - sounds counterintuitive but walking daily (about two miles) can stave off my fatigue enough that I can get some other things accomplished and try a combo of a magnesium cream for muscle aches and compression socks at night when you have a particularly bad leg night. Sometimes helps.

    Have you discussed lowering your dose at all given your level of symptoms with it?

  • dani444
    dani444 Member Posts: 215

    DVCmom3- I totally understand, I have had terrible fatigue on tamoxifen. I am currently on a break from taking it. I am going to try 6 weeks off and see how I feel. My mammaprint was low risk, but I am clinically high risk. My MO did say I could try 10 mg as she thought something was better than nothing. As rah mentioned magnesium lotion might help, it does make a difference for me with the leg cramps. I have literally thought about quitting this drug nearly every day since the SE’s have decreased my QOL. I am sorry you are struggling.

    On a side note, my sister is a DVC member and I just got to tag along for a stay at Disney’s vero beach resort! Have you and your family stayed there??