Brain fog isn’t a medical condition itself, but rather a symptom of other medical conditions. It’s a type of cognitive dysfunction involving:

• memory problems
• lack of mental clarity
• poor concentration
• 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 doesn’t have to be a permanent fixture in your life.

What are the causes of brain fog?

There are numerous explanations for why brain fog occurs. 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. 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 also interfere with how well your brain functions. 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. 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 level during menopause can cause forgetfulness, poor concentration, and cloudy thinking.

4. Diet

Diet can also play a role in brain fog. Vitamin B-12 supports healthy brain function, and a vitamin B-12 deficiency can bring about brain fog.

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

• MSG
• 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 the drug. 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 longer than six months.

People who have fibromyalgia may experience similar fogginess on a daily basis.

Other conditions that may cause brain fog include:

• anemia
• depression
• diabetes
• Sjögren syndrome
• migraines
• Alzheimer’s disease
• hypothyroidism
• autoimmune diseases such as lupus, arthritis, and multiple sclerosis
• dehydration

How it’s diagnosed

See your doctor if you have persistent lack of clarity that worsens or doesn’t improve. A single test can’t diagnose brain fog. Brain fog may signal an underlying issue, so your 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:

• abnormal 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, such as X-rays, MRI, or 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.

How to treat it

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, your 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 brain power (try volunteering or solving brain puzzles)
• finding enjoyable activities
• increasing your intake of protein, fruits, vegetables, and healthy fats