Anastrozole and insomnia



Since starting Anastrozole, I’ve been troubled with chronic insomnia. Has anyone else had this problem?


I’ve experienced insomnia quite a lot in the past, but never night after night as I do currently. I’ve adjusted my bedding so that I can easily throw off a layer, so hot flushes are manageable. If I’m very achey I take painkillers, but I haven’t had too many aches and pains except at the base of my neck, on the opposite side to the radiotherapy treatment. 


Insomnia isn’t listed as a side effect but it’s wearing me down. I feel I’ve coped well with chemo and radiotherapy, but the thought of five years of this is unbearable.

Hi Suze65
I did struggle dreadfully with insomnia when I first started. I originally took at night time, to avoid nausea during the day. As that’s now passed the oncologist I saw at review suggested I switch to taking in the morning, as I’ve been struggling with fatigue during the day. It’s difficult to tell if fatigue is any better, as I’m fighting a winter cold. I have, however, noticed I’m sleeping better at nighttime. Some people find different brands have different effects also. Good luck it does seem to have different effects on each of us x

Hi Suze, I was anastrozle for 4 months, during that time I was suffering with horrendous night sweats and flushes and was wide awake most of the night.  The Oncologist took me off it sayi g my body couldn’t take it.  Since coming off it Im still hot flushing, sweats not so bad but am dropping off to sleep inbetween flushes which I wasn’t when taking it.  I have heard that others have had the same problem sleeping when taking it.  Good luck xx

Hi I’m afraid I’m not going to be positive either. I’ve been on Anastrozole since May & I don’t sleep well at all. 3 or 4 in the morning is my usual awake time & then I find it hard to get off again. It’s not always because of the hot flushes either although these get worse after my monthly Zoladex injection. I usually find myself needing to have a quick 40 winks around 4ish in the afternoon which I know isn’t ideal as it affects the nights sleep again but some days I’d not be able to cope if I didn’t do this. Sorry I can’t offer you any positive advice I hate being negative x

Hi Suze,  no, Not On an alternative.  Onc, just. Said obviously your body can’t handle them and taking them is on,y a 2% improvement of your chances of it not coming back so it’s a case of taking them for the 2% improvement or the greater risk of becoming ill because of lack of sleep/anxiety etc.  bNC  nurse was not happy so suggested a break while things settle.   Still not getting much sleep because of hot flushes, so guess it’s not all down to anastrozele, however, I do sleep inbetween flushes, as when taking it I was wide awake once first flush kicked in.  Sorry can’t offer most positive info.  I am now considering whether to give them another try or not as others seem to be ok on them after a few teething problems xx

Hi Lesley,

I’m interested in the 2% statistic regarding likelihood of relapse. I thought it was a much greater protection but I’ll do some more research. I’ve now got sleeping pills but don’t want to take them long term. Thank you for getting in touch.

Good luck Suze.  The 2% might have just been my percentage and not general, I didn’t ask xx

Hi Ladies,

Just picked up on this thread as I am having trouble sleeping and taking Anastrozole (3 1/2  weeks). I have had periods of insomnia in the past so thought at first it was my normal routine returning but I’m not so sure now - also feeling down today after gradually going up. Wondering whether to take in morning instead? x Jak

I’ve been taking a anastrozole since my op in November , and not too bad so far a few  aches and pains 

 But yes wake up in the early hours every night  and can’t drop back off :( 

I’ll Just have to put up with it I surpose , I tell myself if the tablets stop the cancer returning then I’ll keep on taking them. 


Take care x

Not sure if my 5 penneth is helpful. I’ve been taking it for just over 4 months. Initially I took it at bedtime and really struggled with sleep. My oncologist suggested I swap to the morning to try and change the time I felt fatigued (in the afternoon). The fatigue still hits but I am sleeping better at night once I drop off. I get very vivid dreams though ?

I thought I’d update people, as I started this thread.


I’ve now been taking Anastrozole since early December, and it has been a bumpy ride, but things are getting better. The insomnia was the worst side effect for me, and it got so that I really couldn’t function - I felt so exhausted. I was given sleeping tablets by my GP, and either these or Anastrozole gave me a very itchy rash, which didn’t help the sleep problems!


A different GP then gave me an oral antihistamine, which gradually reduced the itching but also had a sedative effect and made me feel like a zombie all day. I was able to sleep but didn’t feel refreshed.


My husband has a blood pressure machine and monitors his BP regularly, so I checked mine a few weeks ago and was alarmed to see that it was very high. I checked it an hour later and it had risen and then later, it had reached 195/122 (it should be about 120/75). My GP saw me quickly and I’m now taking Amlodipine to control BP. I only take that and Anastrozole now. I think Anastrozole can cause increased BP in certain people, so it’s worth keeping an eye on it if, like me, you have had a tendency towards high BP.


This is all a long-winded way of saying that I think the insomnia and other initial side effects are receding as my body adapts to Anastrozole. I slept 8 hours last night for the first time since early December! I’m sure there will be ongoing SEs, but if I’ve had a decent night’s sleep, I feel I can face them.


Best wishes to all you fellow travellers xx

Hello everyone.

I was diagnosed in November2017.Lumpectomy followed by Radiotherapy and commenced Anastrozole.

I to are suffering with fatigue and insomnia plus hot flushes and night sweats.

The insomnia is the worse to cope with.

I take the Anastrozole in the morning but advised to try evening which I havnt as yet because I have read the posts and everyone seems to be different.

When I saw the oncology Nurse last week she said there has been some good reports from ladies with menapausal symptoms using a Lady Care Magnet which fits inside your Knickers over your tummy.

I bought one from Boots £35 on Friday and so far I have only had an odd flush so it’s worth trying.

Apparently they have sold have a million.

Hope this info helps.

Hi Freddie
I also bought a Lady care magnet in anticipation of the dreaded sweats after starting Letrozole.
I haven’t used it as yet as I read some controversy about it affecting hormones. Could I ask if you have done any research on the product? The leaflet says it is fine for ladies post bc and a friend of mine 100% believes in it.
I asked my bcn who had never heard of it and couldn’t advise.
I did intend to ask my oncologist at the next meeting.
I have only had minimal hot flushes so far, but would still like input from anyone who has used or researched the magnets.
Hope your insomnia improves soon.
Best wishes

Hi there. 
I was diagnosed with Breast last year. Started Anastrazole April this year and to start with I had serious hot flushes, then really painfull joints whic I know is a side affect. Trouble sleeping is in the top 3 side affects, for 2 weeks now I have been suffering with insomnia too. I don’t go off to sleep at all. I was taking it at tea time but have been advised to take it in the morning. The breast cancer nurses have suggested changing the brand too, i yet to find out if this works. I’m waiting to see my oncologist to find out if there anything that can be done. So are you just accepting that you won’t sleep while on it?, is there any further advise you’ve been given?