Timing of aromatase inhibitors (AIs) - taking day or night?

Hi @jsparkle42,

I combined your discussion with an existing discussion titled:

"Timing of HRT, anastrozole - taking day or night?"
- https://connect.mayoclinic.org/discussion/timing-of-hrt-anastrozole-taking-day-or-night/

Here, members have discussed how they take their anastrozole (am or pm) and how it has worked best for them.

@kimogi57
I started taking my anastrozole every other morning about two weeks ago. Began it once daily about 2 years, 3 mo ago. Side effects were building so I stared every other day rather than stop. I have read they have clinical trials now to see if a lower dose than 1 mg every day would be better.
Speaking for myself, I do feel better!

My onco score was 10% without and 3% with AI. Finding a different oncologist now and will certainly tell my new doctor soon. Difficult decissions!

I started on Anastrozole first of April. My oncologist told me to take it at night. So far the only side effect I have is my thumb joint is very sore, and probably won’t go away until I am done with my treatment. Hopefully no more side effects.

Started taking letrozole last April 2025. Some hot sweats periodically and hair thinning at first which has gotten better. Something joints but I also have some arthritis so it it hard to tell what is causing what. I take it at night on my oncologists recommendation. It has increased my LDLs so now on a statin since oncology cardiologist says my diet and exercise can’t control it alone and my red yeast rice wasn’t doing it.

I think part of the problem is that many of the "minor" side effects are also related to estrogen variances. As a male pharmacist I can not say I can fully appreciate some of the side effects but most are the same kind of side effects you see with any medication ever studied. I have told my patients that when the studies were done 200 women out of 1000 stopped taking Arimidex due to the side effects which seem like a lot until you consider that 150 out of 1000 in the group taking placebos(nothing) quit the study due to the side effects. Hope that helps

@trixie1313
I have tried all four of the different estrogen blockers Al-Let-Exe and just tried Tamoxifen and I had the worst bone/joint/muscle pain ever, I have had hair loss, headache, severe fatigue, and hot flashes, bone density extremely low, not sleeping at night!
Sunday I was at church and I was soaking wet when church was over (my hair & clothes). I wouldn’t take a family photo because my makeup and hair looked horrible.
I stopped taking the Tamoxifen Tuesday when I got home and called oncologist, the nurse called back and told me to give it a few days break and try the Anastrozole again! My body has been through so much and I was ready to stop! I crushed my ankle and broke tibia and crushed tibia on the right side of left leg into the bone and broke my big toe on left side and also broke a bone on the right side of my right foot the year after double mastectomy and chemo, I had 2 surgeries and stayed in rehab for 7 months! The nurse said I need to try and tolerate one of those four pills to keep my cancer from coming back!!!
I had stage 3 HER+ breast cancer in 2023.
I pray we all can make it through the 5 years. Praying for all my pink sisters ♥️

@farmgirl1556
Yes my weight gain in bad too!

@cancersucks
Unfortunately, it has been for me!

@pktaylor59 Extreme bone/joint pain.

I have been on anastrozole for a little over 3 years now. Fortunately I have had minimal side effects. I do take it in the evening, usually around 7 pm. It seemed to make me tired so my doctor recommended taking it at that time. Weight can be managed by eating a healthy diet and working out regularly. Good luck…it’s better than the cancer returning. I knew someone who refused to take it and her cancer came back. Good luck with your journey and remember there are a lot of us out there.