Brain Fog: Symptoms, Causes and What Helps

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Almost everyone has days when their thinking feels slow and cloudy. When that feeling sticks around, it is worth looking at why. Here is what brain fog is, its symptoms and common causes, practical ways to clear it, how long it lasts and when to see a doctor.

What you'll learn

• What brain fog is and what it feels like
• Everyday and medical causes of brain fog
• How to get rid of brain fog
• How long it lasts and when to see a doctor

What is brain fog?

"Brain fog" is a term for a range of symptoms that affect your ability to think clearly, focus, remember and pay attention (Cleveland Clinic). It is not a medical diagnosis on its own. It can happen after an illness, as a side effect of a medication or as a symptom of an underlying condition, and it is usually temporary (Cleveland Clinic).

Brain fog symptoms

Brain fog feels a little different for everyone. Common symptoms include (Cleveland Clinic):

• Difficulty concentrating or focusing
• Forgetfulness
• Losing your train of thought
• Not finding the right words
• Slow thinking and reaction time
• Trouble paying attention
• Mental exhaustion and fatigue
• Confusion

What causes brain fog?

Common causes include not enough sleep, ongoing stress, dehydration and poor nutrition, and often more than one is at play.

There are many possible causes, and often more than one is at play. Some of the most common are everyday habits you can change:

• Not enough sleep. Lack of sleep is one of the most common causes (Cleveland Clinic). Adults need 7 or more hours a night (CDC), and research on sleep deprivation shows the biggest effects on attention (Lim and Dinges, 2010).
• Stress. Ongoing stress is a common cause of brain fog (Cleveland Clinic).
• Dehydration. A review of 33 studies found dehydration impairs attention and other thinking tasks, especially when people lose more than 2% of their body weight in water (Wittbrodt and Millard-Stafford, 2018).
• Poor nutrition. Poor nutrition can contribute (Cleveland Clinic). Vitamin B12 deficiency, for example, can cause tiredness, confusion and poor memory, though symptoms can take years to appear (NIH Office of Dietary Supplements).
• Alcohol. During a hangover, attention and decision-making can be impaired, and symptoms can last 24 hours or longer (NIAAA). See how long a hangover lasts.
• Caffeine too late in the day. Caffeine close to bedtime can cut into your sleep (Gardiner et al., 2023), which can leave you foggier the next day. See how much caffeine is too much.

Brain fog can also be linked to health conditions and treatments (Cleveland Clinic):

• After COVID-19. Difficulty thinking or concentrating, sometimes called brain fog, is one of the most commonly reported symptoms of long COVID (CDC).
• Hormonal changes, such as during pregnancy or menopause.
• Mental health conditions such as anxiety and depression.
• Diabetes and low blood sugar.
• Autoimmune conditions such as lupus, multiple sclerosis and fibromyalgia.
• Medications and treatments, such as chemotherapy, or after a long hospital stay.

Because the list is long, a health care provider is the right person to help you work out what is behind brain fog that does not go away.

How to get rid of brain fog

There is no specific treatment for brain fog (Cleveland Clinic). What helps most is dealing with the cause. These everyday steps are a good place to start:

1. Protect your sleep. Aim for 7 or more hours a night (CDC) and keep caffeine to earlier in the day; research suggests finishing a typical cup of coffee at least 8.8 hours before bed (Gardiner et al., 2023).
2. Eat regular, nutritious meals (Cleveland Clinic).
3. Drink enough water, especially in the heat, during exercise or after drinking alcohol (Wittbrodt and Millard-Stafford, 2018).
4. Move every day. Cleveland Clinic suggests about 30 minutes of physical activity a day (Cleveland Clinic), and activity has immediate benefits such as lower anxiety and better sleep (U.S. Department of Health and Human Services).
5. Take short breaks during long stretches of mental work (Cleveland Clinic).
6. Write things down so you don't have to hold everything in your head (Cleveland Clinic).
7. Manage stress, and consider talking therapy such as cognitive behavioral therapy if stress, anxiety or low mood are part of the picture (Cleveland Clinic).
8. Go easy on alcohol, since hangovers impair attention (NIAAA).

No supplement has been shown to cure brain fog. If a deficiency such as low vitamin B12 is the cause, a provider can test for it and recommend treatment (NIH Office of Dietary Supplements).

How long does brain fog last?

Brain fog may last a few days to weeks, and sometimes months or longer, depending on the cause.

It depends on the cause. Brain fog may last a few days to weeks, and in some cases months or longer (Cleveland Clinic). Fog from a short night or a hangover usually clears once you rest and recover; fog linked to an illness or health condition may take longer and usually improves as the underlying cause is treated.

When to see a doctor

Talk to a health care provider if brain fog is disrupting your daily life, for example if you often forget appointments, have trouble finishing ordinary tasks or find it hard to pay attention when someone is talking to you (Cleveland Clinic). Also see a provider if it comes with other symptoms such as ongoing fatigue, numbness or tingling, or low mood.

Call 911 right away for sudden confusion, trouble speaking or understanding speech, sudden numbness or weakness on one side of the body, sudden trouble seeing or walking, or a sudden severe headache. These can be signs of a stroke (CDC).

Common myths (quick reality check)

• Myth: Brain fog is a medical diagnosis. Reality: It is a description of symptoms, not a condition on its own. The cause can be as simple as poor sleep or as involved as a health condition.

• Myth: More coffee will clear brain fog. Reality: Caffeine can't fix the cause, and caffeine late in the day can cut into sleep, which can make the next day foggier.

• Myth: A supplement can cure brain fog. Reality: No supplement has been shown to cure brain fog. If a deficiency is the cause, a provider can test for it and treat it.

• Myth: Brain fog always means something serious. Reality: It is often temporary and linked to sleep, stress or other everyday factors. But sudden confusion or trouble speaking is an emergency.

Frequently asked questions (FAQ)

What is brain fog?

Brain fog is a term for symptoms that affect your ability to think clearly, focus, remember and pay attention. It is not a diagnosis on its own and is usually temporary.

What causes brain fog?

Common causes include lack of sleep, stress, dehydration, poor nutrition, hangovers and hormonal changes. It can also follow COVID-19 or be linked to conditions such as depression, diabetes or autoimmune disease, or to medications.

How do I get rid of brain fog fast?

There is no instant fix. Drinking water, eating a balanced meal, taking a short break and getting some movement may help in the moment, and better sleep helps over the following days. Treating the underlying cause matters most.

How long does brain fog last?

It depends on the cause. It may last a few days to weeks, and in some cases months or longer.

Can dehydration cause brain fog?

Yes. Dehydration can impair attention and other thinking tasks, especially when you lose more than 2% of your body weight in water.

Can lack of sleep cause brain fog?

Yes. Lack of sleep is one of the most common causes. Adults need 7 or more hours a night.

Can vitamin B12 deficiency cause brain fog?

It can. Symptoms of vitamin B12 deficiency include tiredness, confusion and poor memory. A health care provider can test your levels.

When should I worry about brain fog?

See a provider if it lasts or disrupts your daily life. Call 911 for sudden confusion or trouble speaking, which can be signs of a stroke.

Related guides

• How much caffeine is too much?
• How to avoid a caffeine crash
• Why does coffee make me tired?
• How long does a hangover last?
• What is a nootropic? What the evidence supports

Disclaimer and when to seek help

This article is for general education and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Our products are not intended to diagnose, treat, cure, or prevent any disease. Brain fog can be a symptom of a health condition. See a health care provider if it lasts or affects your daily life, and call 911 for sudden confusion, trouble speaking, or numbness or weakness on one side of the body.

References

1. Cleveland Clinic. "Brain Fog: What It Is, Causes, Symptoms & Treatment." Medically reviewed, last updated May 14, 2024.
2. Centers for Disease Control and Prevention. "About Sleep."
3. Centers for Disease Control and Prevention. "Long COVID Signs and Symptoms."
4. Centers for Disease Control and Prevention. "Signs and Symptoms of Stroke."
5. Lim J, Dinges DF. "A meta-analysis of the impact of short-term sleep deprivation on cognitive variables." Psychological Bulletin, 2010;136(3):375-389. doi:10.1037/a0018883
6. Wittbrodt MT, Millard-Stafford M. "Dehydration impairs cognitive performance: a meta-analysis." Medicine & Science in Sports & Exercise, 2018;50(11):2360-2368. doi:10.1249/MSS.0000000000001682
7. NIH Office of Dietary Supplements. "Vitamin B12: Fact Sheet for Consumers."
8. National Institute on Alcohol Abuse and Alcoholism. "Hangovers."
9. U.S. Department of Health and Human Services. "Top 10 Things to Know About the Second Edition of the Physical Activity Guidelines for Americans."
10. Gardiner C, et al. "The effect of caffeine on subsequent sleep: A systematic review and meta-analysis." Sleep Medicine Reviews, 2023;69:101764. doi:10.1016/j.smrv.2023.101764