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9 Possible Causes Of Persistent Brain Fog

Medically reviewed by 
9 Possible Causes Of Persistent Brain Fog

Brain fog is a common complaint in our modern world. "Brain fog" isn't a medical condition but is a term used for specific symptoms that can affect your ability to think. A functional medicine approach to brain fog involves determining the patient's exact root cause and addressing it with an individualized approach based on an in-depth intake questionnaire and specialty lab results.


Signs and Symptoms of Brain Fog

While there are no formal medical diagnostic criteria for brain fog, it is typically characterized by a constellation of several symptoms, including:

  • Difficulty concentrating
  • Difficulty multitasking
  • Forgetfulness
  • Short term and long term memory loss
  • Cognitive impairment
  • Feeling spacy or confused
  • Word-finding difficulties
  • Mental exhaustion or fatigue

It is important to recognize that these symptoms can be attributed to many health conditions or may separately be a signal of a more serious underlying health condition. Please discuss any concerns you have with your functional medicine or healthcare provider.  

Possible Underlying Causes of Brain Fog

There are numerous possible root causes of brain fog. Below are some of the more common reasons.

Prescription medications

Many prescription medications can cause decreased cognition. Sedatives, sleep medications, pain medications, antihistamines, bladder control medications, and others often come with the side effect of dizziness or sleepiness. Polypharmacy, which is becoming increasingly common in the current healthcare system, increases the risk of harmful side effects, including decreased mentation, and this tends to worsen as you age.  

Lifestyle Factors

Stress and sleep quality have a significant impact on overall health.

Chronic stress can cause hormonal imbalances that affect the body in various ways.

The body and brain complete a self-cleaning cycle of removing toxins during sleep. When this is unable to occur due to lack of quality sleep, it can result in brain fog.  

Leaky Gut

The Gut-Brain axis plays an important role in the body's overall health. If you have GI symptoms such as excess gas, bloating, fullness after eating, constipation or diarrhea, and food intolerances, these may be symptoms of a leaky gut.

Food Sensitivities

Brain fog is a common symptom for people with celiac disease and non-celiac gluten sensitivity. While the link between gluten and brain fog is not fully understood, it is a well-documented symptom of people with gluten sensitivity.

Nutrient Deficiencies

A poor diet can also be a factor in the development of brain fog. Poor quality food, high in simple carbohydrates, trans fats are loaded with artificial food additives, causes inflammation in the body. This inflammation can cause brain fog symptoms. Additionally, nutrient deficiencies, particularly vitamin D and B vitamins, are associated with brain fog.

Sleep Disordered Breathing

Sleep-disordered breathing is a more common occurrence than previously thought and, as of 2018, affects upwards of 100 million people worldwide. Obstructive sleep apnea remains the leading type of sleep-disordered breathing and affects up to 50% of men and 31% of women worldwide. Sleep apnea is a potentially serious sleep disorder in which breathing repeatedly stops and starts. You may not be getting adequate oxygen to your brain and other vital organs during this time nor restful, restorative sleep. This leads to grogginess and fatigue the next day.

Mold and Heavy Metal Toxicity  

External toxicants such as mold or heavy metals can cause brain fog. Some molds produce chemicals that can lead to brain fog. Heavy metal toxicity, such as too much mercury and aluminum, has long been linked to brain fog symptoms.

Post-Viral Syndrome

Viruses, such as the COVID-19 virus, can cause systemic inflammation. The COVID-19 pandemic has brought brain fog to the forefront as a symptom of COVID long-haulers syndrome. While it is not possible to test for every virus we're exposed to or prove that the brain fog you're experiencing is related to COVID-19, the good news is that the treatment is the same, and with time, symptoms should improve.

Menopause & Perimenopause

Brain fog is a common complaint for women going through perimenopause and menopause. Fluctuating hormone levels, particularly estrogen shifts, during this time not only affect energy levels but can cause symptoms such as forgetfulness, difficulty concentrating, and brain fog.

Functional Medicine Labs to Find the Root Cause of Brain Fog

Many functional medicine lab tests are beneficial in determining if an underlying condition is causing brain fog symptoms.

Toxin & Toxicity Testing

Inflammation and Chronic disease Testing

  • Inflammatory markers:
  • hs-CRP is a good marker of inflammation and cardiovascular risk. Goal level <0.9 mg/dL
  • homocysteine (goal <7)  
  • Insulin resistance and/or diabetes panel (Test for Hgb A1C, Insulin, and fasting glucose levels)  
  • Goals: Fasting insulin <5.5 micro IU/m
  • Hgb A1c 4.0-5.3%
  • Fasting blood glucose 70-90 mg/dl

Leaky Gut and Gut Microbiome Testing

Food Sensitivity Testing

Nutrient Testing

  • Optimal Vitamin D 50-80 ng/mL

Sleep Apnea

  • Sleep apnea is very common and is characterized by daytime sleepiness and mental fatigue. It is very easy to do an at-home sleep study test to determine if you have sleep apnea. Treatment is very effective, and you may be surprised at how good you feel after getting a restful and restorative night's sleep!

Liver Function

  • It is also good to check liver function, as the liver is the body's main detoxification organ. If it is not functioning properly, even small amounts of toxins can build up over time. (AST and ALT goal levels < 25)

Functional Medicine Treatment for Brain Fog

Treatment for brain fog aims to treat any underlying health conditions that are contributing to the symptoms. For example, if you are deficient in Vitamin D, restoring the body to a functional level can help reduce brain fog symptoms.  

Food as Medicine

Whole foods and anti-inflammatory diets, such as the MIND Diet or Keto-Flex, have been shown in many research studies to help reduce total body inflammation and improve cognitive function.


While a food-first approach is generally recommended in functional medicine, anti-inflammatory and antioxidant supplements can help reduce inflammation in the body that may be contributing to brain fog.

Turmeric, Omega 3 fatty acids, CoQ enzyme 10, Glutathione, and NAD can be helpful in the short term. Prebiotics, probiotics, and glutamate can be essential for gut healing and support.

Lifestyle Changes

Positive lifestyle changes support reducing brain fog and promote healing. Adequate sleep is vital in brain healing and reduces the overall stress burden. Daily physical activity and movement help with hormonal balance, detoxification, and gut health and decreases systemic inflammation. Stress management is also a key factor. There are many ways to incorporate stress reduction into your daily routine.  

Reducing or limiting pharmaceuticals can also help decrease polypharmacy and side effects from medications. Be sure to talk with your health care provider before making any changes to your prescription medications.



There are many potential causes of brain fog, and uncovering what may be happening with your body is the key to reversing the symptoms. Utilizing a functional medicine approach, reducing exposure to toxins, managing stress, prioritizing sleep, eating a healthy diet of a variety of whole colorful foods, limiting pharmaceutical medications, and incorporating movement into your daily routine can help improve brain fog symptoms.  

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
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