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Many people with cancer have thinking and memory problems. Chemo brain or chemobrain is a term for these symptoms. But what it means may surprise you.

What Is Chemo Brain?

Most people think of chemo brain as cognitive dysfunction, or thinking problems, caused by chemotherapy. Only part of that is true. Chemo brain is a common side effect of chemotherapy, according to the American Cancer Society (ACS).

MRI brain studies of people receiving chemotherapy show decreases in activity in their brain’s frontal attention network. That’s according to a meta-analysis published in Neuroscience & Biobehavioral Reviews.

But if you have cancer, chemotherapy isn’t the only thing that can cause or increase your risk of chemo brain. And chemobrain can also happen before, during, and after cancer treatment, according to the National Cancer Institute.

Other cancer treatments that cause chemo brain

Other cancer treatments can also cause chemobrain or cancer-related brain fog, such as changes in focus, thinking, and memory. These include:

• Cancer surgery.
• Hormone therapy.
• Immunotherapy.
• Radiation therapy.
• Targeted drug therapy.

Medicines for managing treatment side effects, such as steroidal, anti-nausea, or pain medicine, can also trigger cognitive symptoms.

What Are Chemo Brain Symptoms?

Symptoms of chemo brain fog include:

• Difficulty concentrating or focusing on tasks.
• Difficulty making decisions or planning activities.
• Feeling disorganized.
• Feeling like you’re thinking more slowly or can’t think well.
• Losing track of what’s going on around you or having a short attention span.
• Problems with memory loss or with remembering things, such as dates or names.
• Problems paying attention or learning new things.
• Struggling with finding the right words or doing simple math.
• Trouble multitasking. For example, you can’t type notes while in a virtual office meeting.

Am I at Risk for Chemo Brain?

If you have cancer, other factors can increase your risk of chemobrain before, during, and after cancer treatment. According to the ACS, risk factors for chemo brain fog include:

• Alcohol or other substance use.
• Anemia, or low red blood cell count.
• Cancer or cancer treatment symptoms, such as fatigue, pain, or trouble sleeping.
• Chronic conditions, such as diabetes or high blood pressure.
• Hormone changes, such as if you are in perimenopause or postmenopause. Chemotherapy and other cancer treatments can cause early menopause.
• Infection. Some chemotherapy and cancer treatments can increase your risk of infection by lowering your white blood cell count, a condition called neutropenia.
• Mental health issues, such as anxiety, depression, or stress.
• Not eating enough or getting enough nutrients. Chemotherapy can affect your taste buds, so you may eat less or only certain foods, leading to malnutrition.
• Older age, or if you’re weak or frail.
• Your cancer type, especially brain tumors or cancer that has spread to your brain.

How Long Does Chemo Brain Last?

How long you feel like you have chemo brain or brain fog may depend on what’s causing it. Different chemotherapy treatments and how often you get chemo can also play a role.

When it comes to chemo brain, you may wonder, does your body ever fully recover from chemotherapy?

In general, you may feel the biggest side effects of chemotherapy the first two to three days after treatment. According to the ACS, it takes about 48 to 72 hours for your body to break down chemotherapy drugs.

Some types of chemo may take longer to leave your body, so recovery may take longer. Ask your cancer doctor or nurse navigator what you can expect from the chemotherapy drugs in your treatment plan. This can help you plan around when you may not feel your best.

Does chemo brain go away?

Often, brain fog symptoms go away after treatment ends. For others, chemobrain can last long after treatment. Again, it depends on what’s causing your chemobrain, including your personal risk factors and what kind of cancer treatment you receive.

With prolonged chemo, an estimated 70% to 75% of cancer patients develop cognitive decline during and after chemo, according to a review published in Advances in Cancer Research. Of these, up to 50% have long-lasting effects of brain fog for months or even years.

How can you manage chemo brain fog?

Chemo brain fog can feel frustrating. It can also start to affect how you live your life. These steps may help you manage minor memory or concentration problems:

• Use a daily or digital planner to write down and help you remember important activities, names, phone numbers, and information.
• Do things that require a lot of concentration earlier in the day, when you’re feeling rested and your mind is still “fresh.”
• Get regular exercise or physical activity, which can help reduce stress during cancer treatment. Ask your cancer care team what exercises are safe for you during treatment.
• Practice good sleep hygiene. Adults should aim for at least seven hours of sleep. Avoid long naps, which can get in the way of nighttime sleep.

When Should I Talk to a Doctor About Chemobrain?

If you’re going through cancer treatment, let your cancer doctor or care team know about any side effects, including chemobrain. Tell them about any other problems you’re having, such as not eating or sleeping well. Also, let them know of any medications or supplements you take that aren’t in your treatment plan.

If you’ve finished your cancer treatment, let your primary care provider know what you’re feeling. They can ensure nothing else is going on with your health that may impact your brain functioning.

Can doctors treat chemobrain?

Your doctor will go over your symptoms to advise you on the best ways to manage your chemobrain. Sometimes treating risk factors, such as anxiety, depression, poor nutrition, or poor sleep, can help relieve the feeling of brain fog.

Doctors are also studying whether certain interventions, including antidepressants and transcranial stimulation, may help people with long-term chemo brain. If brain fog is affecting your quality of life, ask your doctor whether joining a clinical trial is right for you.

Editor's Note: This article was originally published on January 27, 2025, and was last reviewed on January 2, 2026.