Anyone have headaches while on an aromatase inhibitor (AI)?

In researching my own issues, I found that vasoconstriction caused by an AI can cause headaches. You might check with your doctor if this could be the cause, and if there is something that might help relax the vascular system.
It seems doctors don't address the side effects that don't meet the scientifically “significant” level - that is, not enough people have them or the effects aren't severe enough. You're probably in the “not enough people have it” category.

It could be that the level of vasoconstriction is dose dependent, so if a lower dose would still protect you based on your cancer profile, then that might help. There are foods that are supposed to induce vasodilation (beets, spinach, citrus, garlic) but I don't know if you could eat enough to help. There are also supplements that increase vasodilation but you'd want to check with the doctor before taking.

I have the opposite effect on tamoxifen, because I’m old. It acts as an agonist (positive force) and causes vasodilation in the brain vascular system causing headaches. My tamoxifen dose was lowered by the oncologist and my regular doctor recommended a nasal spray that induces vasoconstriction. My headaches stopped.

Thank you triciaot for your very helpful and on-point thoughts.
I was/am between a rock and a hard place with the recommended AI's for treatment of my breast cancer. It was the only recommendation for my treatment post-BM. I have ischemic heart disease since my 50s and really shouldn't even be on the AI's because of (as you mentioned) the vasoconstrictive effects. I am at risk for a heart attack or stroke. One of my cardiologists who I hold in high regard reluctantly gave his "OK" to treat my breast cancer as recommended. I will be seeing my breast oncologist in 2 weeks and will be discussing this issue with her. Wonderful to hear your headaches stopped. The very best to you!

Yes. Headaches is a potential SE of AI Inhibitors.
I started Anastrozole in January of this year (2026. The year of your comment isn't displayed, so I am assuming) and within two weeks I was experiencing more more frequent and intense, headaches. I've had H/A all of my life, but some went away after my hysterectomy years ago. Those that remained were "doable" with Chiropractic care.
Now, I have daily H/A.
Also, mild GI but that ebbed. Hot flashes- but doable. About 3-4 weeks on Anastrozole I had sudden, extreme, bilateral foot pain, hips and low back. Initially, I thought a weather change was coming because I am very susceptible to barometric pressure. I have been for many years. But, NEVER, have I had pain in both feet/ankles at the same time. I could not sleep. This lasted until I quit the medication - with by doc's okay, in early April. My Oncologist, whom I saw last week, wants me to start on Letrozole (should arrive in the mail this week). His game plan is, if the pain returns to start me on Cymbalta.... OH! I had horrible, generalized 2+ - 3+ pitting edema too, and continue to be 10# heavier than normal, despite most of the edema going away--with the aid of Furosemide.
Reading a few of the comments here (I just joined. Literally), and I already knew this from previous research, I do not think I will tolerate the Letrozole any better than Anastrozole, but I will think positively. I have had three separate cancers in the past 15 years (four, technically, as I had two separte breast tumors, Stage I and Stage II, respectively, IDC. Had a double mastectomy in Dec. '25, a Radical Nephrectomy in Sept. '25 (RCC) and RAD/CHEMO in 2011 for Stage II anal CA, SCC.

Well, we should start the AI Headache Club.
Your story sounds like mine in the sense I started on Anastrozole, went to Letrozole and now on the last of the group Exemestane - changes all due to awful daily headaches usually striking early evenings - just when I want to relax and watch some TV with my husband.
Hope you will get relief from the H/As with Letrozole, remember we all respond differently to any medication.
I can tell you I feel better on Exemestane headache-wise.
I still get them but not as bad and can cope. But I also get sudden, very sharp pains in my head, lasting maybe 20 seconds or so (this was from the get-go with the AIs). If it became something lasting more it possibility could be a 911 call. It's that bad.
You have gone/is going through a real battle with all your cancers. I wish you nothing but the best going forward.
One day, one step, one moment at a time. Prayers for you and God Bless.

Yes!! Anastrozole caused horrible headaches. Now on Toremifene and the headaches resolved.