Brain fog is a symptom that can be caused by stress, sleep changes, medications, and other factors. It can cause confusion, memory issues, and a lack of focus.

Brain fog itself is not a medical condition but instead a symptom of other medical conditions. It’s a type of cognitive dysfunction involving:

  • memory problems
  • a lack of mental clarity
  • poor concentration
  • an inability to focus

Some people also describe it as mental fatigue. Depending on the severity of brain fog, it can interfere with work or school. But it does not have to be a permanent fixture in your life.

There are several explanations for why brain fog happens. Once you identify the underlying cause, you can begin fixing the problem. Here are six possible causes.

1. Stress

Chronic stress can increase blood pressure, weaken the immune system, and trigger depression, according to 2017 research. It can also cause mental fatigue.

When your brain is exhausted, it becomes harder to think, reason, and focus.

2. Lack of sleep

Poor sleep quality can interfere with how well your brain functions, according to 2021 research. Aim for 8 to 9 hours of sleep per night.

Sleeping too little can lead to poor concentration and cloudy thoughts.

3. Hormonal changes

Hormonal changes can also trigger brain fog, according to 2018 research. Levels of the hormones progesterone and estrogen increase during pregnancy. This change can affect memory and cause short-term cognitive impairment.

Similarly, a drop in estrogen levels during menopause can cause forgetfulness, poor concentration, and cloudy thinking, according to 2019 research.

4. Diet

Diet can also play a role in brain fog. Vitamin B12 supports healthy brain function, and a vitamin B12 deficiency can bring about brain fog, according to a 2021 research review.

If you have food allergies or sensitivities, brain fog may develop after eating certain foods. These include:

  • aspartame
  • peanuts
  • dairy

Removing trigger foods from your diet may improve symptoms.

5. Medications

If you notice brain fog while taking medication, talk with your doctor. Brain fog may be a known side effect of these medications, according to 2021 research. Lowering your dosage or switching to another drug may improve your symptoms.

Brain fog can also occur after cancer treatments. This is referred to as chemo brain.

6. Medical conditions

Medical conditions associated with inflammation, fatigue, or changes in blood glucose level can also cause mental fatigue. For example, brain fog is a symptom of chronic fatigue syndrome, which involves persistent fatigue for a prolonged period of time, according to 2020 research.

People who have fibromyalgia may experience similar fogginess on a daily basis, according to a 2015 research review.

Other conditions that may cause brain fog include:

Talk with a doctor if you have a persistent lack of clarity that worsens or does not improve.

A single test cannot be used by a doctor diagnose brain fog. Brain fog may signal an underlying issue, so a doctor will conduct a physical examination and ask about your:

  • mental health
  • diet
  • level of physical activity
  • current medications or supplements

You should let your doctor know about other symptoms you might have. For example, someone with hypothyroidism may have brain fog along with hair loss, dry skin, weight gain, or brittle nails.

Blood work can help your doctor identify the cause of brain fog. A blood test can detect the following:

  • irregular glucose levels
  • poor liver, kidney, and thyroid function
  • nutritional deficiencies
  • infections
  • inflammatory diseases

Based on the results, your doctor will determine whether to investigate further. Other diagnostic tools may include imaging tests to look inside the body, like X-rays, magnetic resonance imaging (MRI), or computerized tomography (CT) scans.

The doctor may also conduct allergy testing or a sleep study to check for a sleep disorder.

Keeping a food journal can help you determine if your diet contributes to brain fog.

If you need help finding a primary care doctor, then check out our FindCare tool here.

Brain fog treatment depends on the cause. For example, if you’re anemic, iron supplements may increase your production of red blood cells and reduce your brain fog.

If you’re diagnosed with an autoimmune disease, a doctor may recommend a corticosteroid or other medication to reduce inflammation or suppress the immune system.

Sometimes, relieving brain fog is a matter of correcting a nutritional deficiency, switching medications, or improving the quality of your sleep.

Home remedies to improve brain fog include:

  • sleeping 8 to 9 hours per night
  • managing stress by knowing your limitations and avoiding excessive alcohol and caffeine
  • exercising
  • strengthening your thinking abilities (try volunteering or solving brain puzzles)
  • finding enjoyable activities
  • increasing your intake of protein, fruits, vegetables, and healthy fats

Brain fog can be frustrating, but relief is possible. You should not ignore your symptoms because if left untreated, brain fog can impact the quality of your life. Once the underlying cause is addressed, your mental clarity can improve.