06/16/2026
“Brain fog” is a term for a range of symptoms that cause cognitive impairment. This affects your ability to think clearly, focus, concentrate, remember and pay attention. Like its name, these symptoms cloud your mind and make it difficult to perform routine tasks like holding a conversation, listening to instructions or remembering the steps of something you’re doing.
Brain fog, also called mental fog, can happen after an illness, as a side effect of a medication (like chemotherapy) or as a symptom of an underlying condition. A healthcare provider can help you determine what’s causing brain fog to help you feel more like yourself.
Some common causes include:
-A lack of sleep.
-Autoimmune conditions like lupus, multiple sclerosis and fibromyalgia.
-Diabetes and low blood sugar levels (hypoglycemia).
-Mental health conditions like anxiety or depression.
-Neurodivergent conditions like ADHD and autism spectrum disorder.
-Hormonal changes like during pregnancy or menopause.
-Poor nutrition.
-Stress.
In addition, you may develop brain fog after:
-A COVID-19 infection (long COVID).
-Chemotherapy treatment for cancer.
-Long hospital stays.
Some research shows that your immune system could cause inflammation in your brain (neuroinflammation) that temporarily blocks or makes it more difficult for your body to process information.
