Key takeaways:
Brain fog isn’t a medical condition. It’s a general term people use to describe thinking that feels cloudy or slow.
Causes of brain fog range from sleep problems, stress, and hormonal changes to medications, vitamin deficiencies, and underlying health conditions.
Getting enough sleep, exercising regularly, eating a balanced diet, and managing stress may help improve brain fog.
If brain fog persists, identifying the underlying cause is an important part of treatment.
Everyone has days in which they feel like they’re not at their best. You feel sluggish or tired, as though you’re in a fog. Sometimes, brain fog is temporary and follows a night of poor sleep or a particularly stressful week.
But brain fog can also be a symptom of a more serious underlying medical condition. Read more to learn about what brain fog feels like, what can cause it, and how to treat it.
What is brain fog?
Brain fog isn’t a medical condition. It’s a general term people use when they feel that their thinking is fuzzy, slow, or less clear than usual.
Think of how you feel in those first moments when you wake up: Your brain is slow to process, everything seems a little foggy, and even your body moves a little slowly. Brain fog can feel similar, but it may last much longer than ordinary morning grogginess.
What does brain fog feel like?
Brain fog can feel different for everyone. Common symptoms include:
Difficulty concentrating or paying attention: You may have trouble focusing on a conversation, reading a page, or finishing a task.
Forgetfulness: You might lose track of what you were doing or struggle to remember something you just heard.
Fatigue: You may feel physically tired or mentally drained, even after relatively little activity.
Trouble multitasking: Planning your day or juggling several tasks may feel harder than usual. Difficulties with planning and organizing can involve executive function.
Lack of motivation: You may struggle to start tasks that would normally be easy for you.
Confusion: You may have trouble making sense of the world around you or feel a lack of mental clarity.
A feeling of fuzziness: Your head may feel fuzzy in a way that’s hard to explain. Some people describe it as feeling spacey or scatterbrained.
Difficulty finding words: You may know what you want to say but struggle to find the right word.
Causes of brain fog
Brain fog can have many causes, from everyday stress and poor sleep to underlying health conditions. Some causes are temporary and easy to address, while others may require ongoing treatment. The good news is that many causes of brain fog are manageable once you identify what’s behind it. Here are some possible reasons your head might feel fuzzy.
Lifestyle and daily habits
Your daily habits can affect your overall health as well as your brain health. If your brain feels foggy, consider whether any of the following might be playing a role:
Too much stress: Stress can interfere with attention and memory. Some of the most stressful life events include things like divorce, major illness, death of a loved one, and loss of a job.
Sleep deprivation: Even a few nights of not getting enough sleep can leave you struggling to concentrate or remember things.
A diet high in ultraprocessed foods: Eating a lot of ultra-processed food is linked to worse brain function in middle-aged and older adults. This doesn't mean that a particular meal will cause brain fog. But your overall eating pattern may matter for long-term brain health.
Lack of exercise: Spending a lot of time sitting every day may be linked to worse brain health, although the research is mixed. Research does show that regular exercise can help boost memory and concentration.
Hormonal shifts
Hormonal shifts can cause brain fog, too, such as from:
Pregnancy: “Pregnancy brain” is a real thing. One review looked at 20 different studies and found that women who were pregnant had more difficulties with memory and thought processing than women who weren’t pregnant. Some studies suggest these changes persist for at least 2 years.
Menopause: People often think of hot flashes and trouble sleeping when they think of menopause. But brain fog is another common concern. Hormonal changes linked to menopause can lead to trouble with concentration, multitasking, and attention.
Thyroid problems: Your thyroid gland produces hormones that help regulate your metabolism and support brain function. When thyroid hormone levels are too low or too high, you may experience brain fog, trouble concentrating, or memory problems.
Mental health conditions
If you’re experiencing a mental health condition, it can be difficult to think clearly or focus. Sometimes, brain fog can be a sign of:
Anxiety: The relationship between anxiety and brain fog goes both ways. Having brain fog can make you anxious, and anxiety can lead to brain fog. Sometimes, it’s hard to tell which came first.
Depression: Difficulty concentrating is a common symptom of depression. And being depressed can make it harder to remember things. You may also notice changes in sleep or appetite, low energy, or a loss of interest in things you usually enjoy.
Adult attention-deficit hyperactivity disorder (ADHD): ADHD might be playing a role if you feel constantly sidetracked or have difficulty completing tasks. Other ADHD signs are trouble staying focused and poor time-management skills. Some adults have had these symptoms their whole lives. But they only get diagnosed in adulthood when life stressors make it harder to function effectively.
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Other medical conditions
Persistent brain fog can sometimes be a symptom of an underlying medical condition. Possible causes include:
Post-viral syndromes: Brain fog can persist for weeks or months after a viral infection. It’s a recognized symptom of long COVID-19.
Sleep apnea: Sleep apnea causes repeated pauses in breathing during sleep, which can disrupt sleep and lead to brain fog symptoms. Sleep apnea can be diagnosed with a sleep study.
Autoimmune conditions: Conditions such as lupus and multiple sclerosis can affect the brain and nervous system, sometimes leading to problems with memory and concentration.
Celiac disease: Celiac disease is best known for causing digestive symptoms, but it can also affect the brain. Starting a gluten-free diet can help reverse brain fog symptoms.
Neurological conditions: Progressive changes in memory, language, or thinking deserve medical attention. In some cases, these symptoms may be related to Alzheimer's disease or another condition affecting the brain.
Nutritional deficiencies
Your brain needs certain minerals and vitamins to function properly. When levels are too low, you may experience brain fog, as follows:
Vitamin B12: Low levels of B12 can cause memory problems, confusion, and neurological symptoms.
Folate (B9): Deficiency can lead to fatigue, mouth ulcers, and forgetfulness.
Iron: Low iron levels can lead to fatigue, poor concentration, and anemia. Iron deficiency can also cause symptoms without anemia, so a normal hemoglobin level doesn't always rule it out.
Medication side effects
The most common medications that may lead to brain fog include:
Antihistamines: Some allergy medications, particularly older antihistamines such as diphenhydramine (Benadryl), can cause drowsiness and affect attention and memory.
Sleep and anxiety medications: Benzodiazepines and certain sleep aids can cause sedation and memory problems.
Pain medications: Opioids and some other pain medicines can affect alertness and concentration.
Antidepressants: Some can cause drowsiness or other cognitive side effects.
Chemotherapy: Some cancer treatments can cause cognitive symptoms, sometimes called “chemo brain.”
If you think a medication might be contributing to brain fog, talk with your prescriber. Don't stop a prescribed medication without checking first.
How to get rid of brain fog
It’s natural to want a quick fix to clear brain fog. And if there’s an underlying medical reason for your brain fog, your healthcare team may be able to find a relatively simple treatment. But if the reason for brain fog isn’t clear or there’s no known treatment, here are five tips to help lift the fog:
Get more sleep. To help get quality sleep, use your bed just for sleep, keep a regular bedtime, and avoid screens before bedtime.
Move your body. Whether you’re just starting out or looking to increase your workout intensity, exercise can help improve brain health. All exercise seems to help, whether low-intensity or more vigorous.
Eat a balanced diet. Eating a nutrient-rich diet can help support brain health. And certain foods — like leafy greens, eggs, fatty fish, and blueberries — may be especially helpful.
Spend more time outdoors. Nature packs a powerful punch of brain-boosting therapy. It’s not entirely clear why being close to nature benefits brain function, but research indicates a strong link.
Practice stress reduction. When you’re stressed, your body goes into “fight-or-flight” mode, which diverts blood flow to your body rather than your brain. This makes it harder to think. Decreasing stress can reverse that trend. Mindfulness exercises are a great way to lower stress and improve mental fatigue.
Train your brain. Certain “brain-training” activities can help improve concentration and focus. Examples include games like jigsaw puzzles, scrabble, chess, sudoku, and crossword puzzles.
When should you get help for brain fog?
Here are some signs that the cause of your brain fog may be due to an underlying medical condition:
It starts suddenly without a clear reason.
Your brain fog seems to be getting worse with time.
You have trouble completing daily tasks.
Your level of brain fog is interfering with your social relationships or work.
You’re experiencing other unusual physical symptoms, such as weight loss, night sweats, hair loss, diarrhea, unusual rashes, numbness, or tingling.
If you experience these symptoms, contact your healthcare team for an evaluation. They’ll ask you detailed questions about your symptoms and may run blood tests or refer you to a specialist to look for a cause.
Seek urgent medical care for sudden confusion or a sudden change in thinking, especially if it occurs with:
Weakness
Trouble speaking
A severe headache
Other new neurological symptoms
Frequently asked questions
Yes, caffeine can cause brain fog in some people. Caffeine often boosts alertness and concentration. However, too much caffeine can disrupt sleep, trigger anxiety, and activate the body's stress response. These effects may make it harder to focus and think clearly. Caffeine withdrawal can also cause headaches, fatigue, and difficulty concentrating — particularly if you regularly consume caffeine and suddenly reduce your intake.
Brain fog related to grief can last for weeks, months, or sometimes longer. Grief affects people differently. And there’s no set timeline for when concentration, memory, and mental clarity will return to normal. Symptoms may gradually improve as you adjust to your loss, but they can also come and go, especially around anniversaries or other reminders. If brain fog is making daily activities difficult or isn't improving over time, a healthcare professional can help you explore additional support and rule out other possible causes.
Yes, caffeine can cause brain fog in some people. Caffeine often boosts alertness and concentration. However, too much caffeine can disrupt sleep, trigger anxiety, and activate the body's stress response. These effects may make it harder to focus and think clearly. Caffeine withdrawal can also cause headaches, fatigue, and difficulty concentrating — particularly if you regularly consume caffeine and suddenly reduce your intake.
Brain fog related to grief can last for weeks, months, or sometimes longer. Grief affects people differently. And there’s no set timeline for when concentration, memory, and mental clarity will return to normal. Symptoms may gradually improve as you adjust to your loss, but they can also come and go, especially around anniversaries or other reminders. If brain fog is making daily activities difficult or isn't improving over time, a healthcare professional can help you explore additional support and rule out other possible causes.
The bottom line
Brain fog can happen for plenty of reasons, from a few nights of poor sleep to hormonal changes or an underlying medical condition. The good news is that most causes are manageable once you identify them. Pay attention to when your symptoms show up, make time for the habits that support brain health, and check in with a healthcare professional if the fog isn't lifting.
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References
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