Letrozole and icky guts

The icky guts (irritable bowel-type symptoms) come and go. Sometimes are mild and sometimes more long lasting. The problem kicked in after about six weeks of being on letrozole.

With the support of my Onc I came off the medication for Xmas and New Year. The guts were still a bit problematic so I decided it probably wasn’t the medication. Went back on the meds on Tuesday and two daysa later the guts went haywire.

Just wondering if anyone has had a similar reaction. I’ve been checked for an infection, and for bowel and ovarian cancer markers - all clear.


Hi edinburghperson

Just wanted to say that I’ve suffered with my stomach for years and I found out in 2003 (after really being very ill) that I was dairy intolerant and in fact I had some inflamation inside me so they thought I had imflammatory bowel disease. I cut out dairy and the difference was really incredible. Since BC treatment, I started getting symptoms again and then found out I was also gluten and/or wheat intolerant so I had to come off that too. I can now tolerate a small amount of both. Maybe you should be tested for intolerances as this could be the reason or try an elimination diet. Just thought after reading what you’ve said that it might be something for you to think about.

Best wishes
Ruby x

Ruby, Thanks laoads for your reply. I came off dairy the very day I discovered the boob lump and have never looked back. I was wondering if I should get tested for wheat sensitivity/allergy and also wondered if being off dairy and then taking letrozole with lactose in it (only 2.5mg) could be a problem.

You’ve convinced me I should get tested.


Hi Edinburghperson, I have been on Letrozole for just a few months and my guts are causing me mega problems…however I have also had IBS for years and have recently finished 8 months chemo. I too got checked out for a bowel infection ( stool samples) and had bloods done too. Both came back clear. It will be interesting to hear what is causing what. I am also an “Edinburgh” person and attend the WGH. Perhaps we even have the same Consultant? Can we keep in touch to compare notes? Love Val (Scottishlass).

Hi Scottishlass,

Larry is my Onc and I find him very approachable. I think I’ll have the sensitivities/allergies tested privately and then maybe ask if I can have an even lower dose than the 2.5mg of letrozole. Larry thought it was unlikely to be the letrozole as it took six weeks before I had any problems.




I am taking Letrozole but can’t say I have had any problems. However, I did have problems many years ago and happened to read that stress depletes B vitamins, which causes problems in digesting fats, so I started taking them and the problems stopped. I have taken them ever since.

We are all under tremendous stress with bc, so it could be worth a try. Having said that, when I mentioned it to my doctor at the time, she said that with a balanced diet, it wouldn’t be the cause - but then most doctors know very little about nutrition and I am convinced it helped me.

Good luck with resolving your problem. Ann x

Good afternoon Ladies, I do feel for you. Life is so debilitating with a problem gut. I had this problem for many years until last year Jan. After a 3rd operation and a chance magazine artikel I worked it out that my gut/bowel problem was caused by “Antibiotics” which obvioulsy I had been given as standard treatment. I had this artikel confirmed by an anaesthetist. And have since started on acidophilus probiotics and have not looked back since.

Worth giving it your thoughts I hope. All the best.