Brain Fog from Aromatase Inhibitors: What You Need to Know
If you’re taking an aromatase inhibitor (AI) as part of your cancer treatment, you might notice changes in your memory or focus. Many patients describe this as “brain fog.” You’re not alone, and it’s important to know this is a real side effect that many people experience.
What Is Brain Fog?
Brain fog isn’t a medical term, but it describes feeling mentally “cloudy.” People often report:
Trouble remembering things
Difficulty concentrating
Problems finding the right words
Research shows that about half of people on aromatase inhibitors experience these symptoms. However, fewer than half of them tell their doctors. Because of this, some doctors may not realize brain fog is connected to AIs.
Why Does It Happen?
The most likely reason is a drop in estrogen levels. After menopause, your body still has small amounts of estrogen. Aromatase inhibitors reduce those levels to almost zero. Estrogen plays an important role in brain function, so the sudden drop may affect memory and concentration.
Other factors can make brain fog worse, such as:
Age (cognitive changes naturally increase as we get older)
Poor sleep (hot flashes or other sleep issues can make it harder to focus)
Other medical conditions and medications
When Does It Start—and Does It Go Away?
Most people notice brain fog 3 to 6 months after starting the medication. The good news: it often improves after you stop taking the AI, once your estrogen levels return to normal post-menopause levels. However, if other health problems affect memory, those might continue.
How to Cope with Brain Fog
The first step is knowing it’s real—and that it’s not your fault. Here are some tips that may help:
1. Lighten Your Mental Load
Too much on your mind can make it harder to focus. Try a “brain dump”: write down everything on your mind in a notebook or on sticky notes before bed or in the morning.
2. Create Consistent Habits
Put keys, your phone, and other essentials in the same place every time. If you often forget where things are, try changing your routine to make it easier.
3. Use Reminders
Record a quick voice memo or leave notes for yourself. For example, “I’m going to the basement to get a paintbrush.” It may sound simple, but it works.
4. Reduce Distractions
Turn off phone notifications when you need to focus. Our brains often interrupt themselves with distractions, so creating a calm environment can help.
5. Move Your Body
Exercise can boost mental clarity. Aim for moderate activity—where you can talk but not sing—for about 4–5 days a week if your doctor says it’s safe.
6. Try Changing When You Take Your Medication
Some people find that taking their AI after breakfast—instead of first thing in the morning or at night—helps with brain fog. This isn’t proven in studies, but it might be worth trying.
Talk to Your Medical Team
If brain fog is bothering you, bring it up with your doctor. You deserve support and strategies that make life easier during treatment. Remember, you’re not alone in this.
Your Turn
Have you experienced brain fog on aromatase inhibitors? What strategies have helped you? Share your tips and questions in the comments below. And if you need urgent help, reach out to your healthcare team right away.
A long-time practicing oncologist and professor at the University of Michigan, Jennifer has received several awards for her medical excellence and published over 150 original research articles as well as numerous editorials and book chapters. She is also a speaker and advocate, committed to improving the quality of medical care and reducing the barriers to equity among the disenfranchised.
For more information on how HuMOLYTE can support your gut health during chemotherapy, visit our product page or consult your health care provider.
This blog was reviewed by Dr. Sourabh Kharait.
This blog is for educational purposes only and is not intended as medical advice. Always consult with your healthcare provider before making any changes to your treatment plan, hydration strategies, or diet. The information provided here is based on general insights and may not apply to individual circumstances.
