Brain Fog: Understanding the Causes and Finding the Right Solutions

Audio summary of the article using Dr. Kar’s AI-cloned voice

Brain fog is a symptom that can be caused by many conditions and is often severe enough to interfere with daily functioning.

Most people describe brain fog as:

• Feeling as though thoughts are moving through a thick liquid, like honey
• Feeling less sharp than usual
• Having difficulty finding words
• Mental fatigue that makes ordinary tasks feel effortful
• Symptoms may fluctuate from day to day

Research characterizing brain fog across nearly 26,000 participants found that it affects four areas of life (Alim-Marvasti et al., 2024):

• Thinking: difficulty with attention, memory, and processing information quickly
• Emotions: feelings of anxiety or low mood
• Body: fatigue and low energy
• Daily activities: struggling to work, socialize, or manage everyday tasks

Importantly, brain fog is not a normal part of aging, nor is it an early symptom of dementia. There are multiple conditions related to brain fog, and there is no single medication that can cure it. However, several strategies can help manage the symptoms, and the path to improvement begins with understanding what drives them.

This article explores the nature of brain fog, examines the potential underlying mechanisms responsible for it, identifies the conditions that should be ruled out as contributing factors, and outlines practical steps you can take to address it.

Why Does the Brain Feel Foggy? Understanding What Is Happening Underneath

Brain fog may result from several different mechanisms. In most cases, multiple contributing factors may be at play simultaneously, making it important to consider the full picture when seeking relief.

The infographic below illustrates the key mechanisms:

Neuroinflammation and microglial activation:

When the brain’s immune cells, microglia, become persistently activated by infections, autoimmunity, blood sugar dysregulation, or poor sleep, they release pro-inflammatory molecules that impair neuronal communication and cause brain fog. (Denno et al., 2025).

Blood-brain barrier disruption:

The blood-brain barrier controls what enters the brain from the bloodstream. When this protective barrier is compromised, as seen in long COVID, autoimmune conditions, and chronic systemic inflammation, inflammatory molecules and immune cells gain direct access to brain tissue, amplifying cognitive impairment (Greene et al., 2024).

Viral persistence:

In long COVID specifically, SARS-CoV-2 and viral RNA can persist in tissues for months to years, driving ongoing inflammation and immune activation, thereby causing brain fog. (Prakash et al., 2025).

Impaired cellular energy production:

Mitochondria are the cell’s energy-generating machinery. All cells need energy to function. The brain has a very high energy requirement. When mitochondrial function is disrupted by autoimmunity, blood sugar dysregulation, or poor sleep, brain cells cannot generate energy efficiently, producing mental fatigue and slowed processing.

Nutrient deficiencies:

Iron deficiency impairs cognitive function even before anemia develops (Murray-Kolb & Beard, 2007). Vitamin B12 and B complex are essential for neurological function. A low omega-3 index has been associated with cognitive impairment. Several nutrient deficiencies, either in isolation or together, can cause brain fog. (Lukaschek et al., 2016).

Hormonal influences:

Estrogen, progesterone and thyroid hormones directly affect brain glucose metabolism, blood flow, and neuronal function. Fluctuations or decline, as in perimenopause or hypothyroidism, frequently produce cognitive symptoms.

Brain fog can be caused by a wide range of medical conditions. Identifying the underlying cause matters more than treating the symptom alone. The most common conditions include hormonal changes, thyroid dysfunction, nutritional deficiencies, sleep disorders, autoimmune conditions, and post-viral illness — but the full list is considerably longer.

What Conditions Can Cause Brain Fog?

Brain fog can be caused by a wide range of medical conditions. Identifying the underlying cause matters more than treating the symptom alone.

The most common conditions are :

1. Hormonal changes — perimenopause, menopause, and postpartum
2. Thyroid dysfunction
3. Blood sugar dysregulation
4. Ultra-processed food
5. Nutritional deficiencies
6. Sleep disorders
7. ME/CFS and fibromyalgia
8. Long COVID and post-viral illness
9. Autoimmune conditions
10. Migraines
11. Concussion and traumatic brain injury
12. Medication side effects
13. Alcohol and cannabis use
14. Lyme disease

Each of these is explored in detail below.

Are Hormonal Changes Causing Brain Fog?

Perimenopause and menopause are among the most common triggers of brain fog in women. Approximately two-thirds of women report cognitive symptoms during the menopause transition, including

• memory lapses
• difficulty concentrating
• mental fatigue and
• impaired word retrieval

Studies show that between 52 and 90 % of perimenopausal women report concentration difficulties, peaking between ages 50 and 54. The underlying drivers are multifactorial: fluctuations in estrogen and progesterone levels affect hippocampal and prefrontal cortex function, and vasomotor symptoms, sleep disturbance, and mood changes all compound the picture. Importantly, brain fog during menopause does not indicate dementia or Alzheimer’s disease risk. (Gurvich et al., 2026).

Read About Menopausal Brain Fog

Is “Mommy Brain” Real?

Studies show that up to 80% of pregnant and new mothers report memory loss and brain fog. However, neuropsychological testing generally shows only subtle deficits that remain within normal ranges. A 2023 viewpoint in JAMA Neurology argued that the “mommy brain” narrative deserves reframing. The brain changes occurring during the perinatal period may reflect adaptive neuroplastic reorganization rather than cognitive impairment (McCormack et al., 2023). Additional factors like iron deficiency, thyroid dysfunction, and sleep disruption may contribute to brain fog after a recent delivery.

Can Thyroid Dysfunction Cause Brain Fog?

About 10–15% of people treated for hypothyroidism continue to experience brain fog, even when their thyroid levels appear normal on testing. Symptoms often significantly reduce quality of life, yet the exact cause remains unclear. Some patients report improvement with combined treatment using thyroxine (T4, the standard treatment) and triiodothyronine (T3), or desiccated thyroid extracts. The most helpful approach is individualized, combining optimized thyroid treatment with attention to sleep, exercise, nutrition, and cognitive rehabilitation to address persistent symptoms. (Samuels & Bernstein, 2022).

Read about the treatment of hypothyroidism

How Blood Sugar Dysregulation Contributes to Brain Fog

People with type 2 diabetes often report symptoms that resemble brain fog, including difficulty concentrating, slower thinking, and memory lapses. Research has found that higher blood sugar levels are associated with poorer cognitive performance, particularly in areas such as attention, processing speed, and executive function. While many factors can contribute to cognitive symptoms, both short-term glucose elevations and long-term exposure to high blood sugar appear to affect how efficiently the brain functions. (Sommerfield et al. 2004).

Can Reactive Hypoglycemia Cause Brain Fog? The Role of Blood Glucose Decline Rate

Reactive hypoglycemia (RH) occurs when blood glucose drops rapidly 2-5 hours after eating, triggering symptoms such as brain fog, fatigue, confusion, and difficulty concentrating. Importantly, symptoms can occur even when glucose does not fall below the traditional hypoglycemia threshold of 70 mg/dL and can occur in people without diabetes.

Rather than being triggered by specific absolute blood glucose levels, the symptoms of reactive hypoglycemia may be driven by the rate at which blood glucose falls. In other words, the rate of decline may be a more significant factor than the actual glucose value. (Sweatt et al., 2026)
The rapid drop in blood glucose is commonly precipitated by overconsuming carbohydrates combined with insufficient protein intake.

How to find out if this is happening: A continuous glucose monitor (CGM) is the most practical tool. It is a wearable device that tracks glucose levels continuously without requiring finger pricks. Blood glucose levels can be monitored alongside food intake and symptoms.

What to do about it: Modify meal composition by reducing carbohydrates and increasing protein and healthy fat. This slows glucose absorption and prevents the rapid insulin response that triggers the drop.

Do Ultra-Processed Foods Contribute to Brain Fog?

Ultra-processed foods (UPFs) — such as soft drinks, packaged snacks, flavoured cereals, processed meats, and most fast food are high in added sugar, refined carbohydrates, and artificial additives, and low in protein and fibre.

No study has specifically examined the association between eating ultra-processed foods and brain fog, but a large study of nearly 11,000 adults found that higher UPF consumption was associated with cognitive decline that was up to 28% faster than in those who ate the least (Gomes Gonçalves et al., 2023). The likely mechanisms — chronic inflammation, blood sugar dysregulation, and displacement of nutrient-dense food are all independently linked to brain fog.

Can Nutritional Deficiencies Cause Brain Fog?

Common nutritional deficiencies, such as iron deficiency and B vitamin deficiencies, are among the most correctable causes. Iron deficiency impairs cognitive function even before anemia develops (Murray-Kolb & Beard, 2007). Vitamin B12 deficiency produces well-documented neurological and cognitive symptoms. Vitamin D insufficiency has been associated with cognitive impairment, and supplementation in older adults with insufficiency has been shown to improve cognitive function (Yang et al., 2020). Low omega-3 levels have been associated with cognitive impairment in older adults (Lukaschek et al., 2016).

Do Sleep Disorders Cause Brain Fog?

Poor sleep is one of the most important causes of brain fog. If you have experienced even one day of poor sleep, you know what I am talking about.

Sleep challenges are primarily of 3 types:

1. People who don’t prioritize sleep — “I will sleep when I die.”
2. Chronic insomnia–people who have trouble falling and or staying asleep, and it affects their functioning the next day. This is very common during the menopausal transition.
3. Sleep disorders, such as obstructive sleep apnea, occur when a person’s breathing repeatedly stops and starts during sleep — often without their knowledge. While snoring is a common indicator, some people may have sleep apnea without exhibiting this symptom.

To know more about sleep, listen to podcast episodes on sleep.

What Is the Connection Between Fibromyalgia, ME/CFS and Brain Fog?

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex, multi-system condition characterized by profound fatigue, post-exertional worsening of symptoms, sleep disturbance, and cognitive impairment. Brain fog is a central feature, with measurable deficits in processing speed, attention, concentration, and working memory. Fibromyalgia frequently co-occurs with ME/CFS and shares many of the same cognitive features. Up to 75% of people with ME/CFS are women.

Brain Fog as a Symptom of Long COVID

Long COVID, or post-acute sequelae of SARS-CoV-2 infection (PASC), refers to a constellation of symptoms that persist for weeks to months after the acute COVID-19 infection has resolved, even in people with mild initial illness. It affects multiple organ systems and involves more than 200 documented symptoms, with brain fog and fatigue among the most prevalent (Davis et al., 2023).

Brain fog in long COVID is driven by neuroinflammation, disruption of the blood-brain barrier, and viral persistence in tissues. Post-viral cognitive symptoms are not unique to COVID-19; they have been documented after other viral and bacterial infections as well.

Autoimmune Conditions And Brain Fog

Autoimmune conditions are diseases in which the immune system mistakenly attacks the body’s own tissues. There are more than 80 recognized autoimmune conditions, and brain fog is a common feature across many of them. Autoimmune conditions like multiple sclerosis, rheumatoid arthritis, lupus, and Hashimoto’s thyroiditis all feature brain fog as a symptom. In these conditions, neuroinflammation driven by ongoing immune activity impairs cognitive function. Managing the underlying condition is central to addressing the brain fog.

Do Migraines Cause Brain Fog?

In a study of nearly 26,000 people, brain fog was strongly associated with migraines. People with migraines scored 34.1% higher on the migraine-associated disability scale, and long COVID had the strongest overall association with brain fog, followed closely by a history of concussion (Alim-Marvasti et al., 2024). The connection between migraines and brain fog is often missed.

Concussion And Brain Fog

A history of concussion is associated with a more than twofold increased risk of persistent brain fog (Alim-Marvasti et al., 2024). This is frequently underreported and underinvestigated in clinical settings. Head trauma has very serious consequences, even if a person doesn’t lose consciousness.

Some Medications Can Cause Brain Fog

Drug-induced cognitive impairment is a well-established but frequently under-recognized complication of many commonly prescribed medications (Svendsen et al., 2024).

Medication classes known to affect cognitive clarity include:

• Antiseizure medications (gabapentin, pregabalin, valproate)
• Antidepressants (tricyclics such as amitriptyline, SSRIs)
• Antiparkinsonian drugs (levodopa, dopamine agonists)
• Antipsychotics (haloperidol, quetiapine)
• Lithium
• Benzodiazepines and Z-drugs (diazepam, lorazepam, zopiclone, zolpidem)
• Opioids (morphine, oxycodone, tramadol)
• First-generation antihistamines (diphenhydramine, chlorphenamine)
• Drugs for urinary incontinence (oxybutynin, tolterodine, solifenacin)
• Proton pump inhibitors (omeprazole, pantoprazole)
• Glucocorticoids (prednisone, dexamethasone)
• Pain meds (ibuprofen, naproxen)
• Cholesterol meds (atorvastatin)
• Blood pressure meds (beta-blockers)
• Chemotherapeutic agents (cyclophosphamide, methotrexate)

If brain fog develops or worsens after starting or increasing the dose of any medication, a review with the prescribing physician is warranted.

Does Alcohol or Cannabis Use Contribute to Brain Fog?

Yes. Even moderate regular alcohol consumption can impair cognitive clarity, memory consolidation, and sleep architecture. Regular cannabis use has been associated with reduced processing speed and working memory.

Lyme Disease and Brain Fog

Lyme disease is a tick-borne bacterial infection caused by Borrelia burgdorferi, transmitted through the bite of an infected tick. In some people, brain fog, memory difficulties, and difficulty concentrating persist even after antibiotic treatment for Lyme disease(Brackett et al., 2024). This is more prevalent than previously recognized and is present in parts of Canada, the United States, and Europe.

What Laboratory Tests Should You Ask For?

There is no single test for brain fog. Lab tests will depend on the medical history, symptom severity, age, and other factors.

Some of the most important ones are

• Complete Blood Count (CBC)

• Iron studies: serum ferritin, serum iron, and transferrin saturation
• Thyroid function: TSH, free T3, and free T4 and thyroid antibodies
• FSH– To confirm menopause. There is no role of testing for estrogens and progesterone in perimenopause when women are still cycling.
• Vitamin B12
• Vitamin D3
• Fasting glucose, fasting insulin, and HbA1c
• High-sensitivity CRP
• Omega-3 index
• Autoimmune markers
• Lyme disease evaluation

Results require clinical interpretation, and this list is a starting point for a conversation with your physician, not a self-directed testing protocol.

What Can You Do for Brain Fog?

Step 1: Talk to a Healthcare Practitioner

The most important first step is to rule out a major underlying medical condition. Check the section above, “What Conditions Can Cause Brain Fog.”

Download the Brain Fog Checklist and take it to your next doctor’s appointment

Step 2: Self-directed Steps

Once major underlying conditions are being investigated or managed, the following steps have meaningful evidence behind them and can be started immediately.

Prioritize Protein at Every Meal

Aim for approximately 1 -1.2 grams of protein per kilogram of body weight per day. One egg contains approximately 7 grams. Vegetarians and vegans will need a quality protein supplement to meet their requirements.

Address Sleep

For chronic insomnia, CBT-I (Cognitive Behavioural Therapy for Insomnia) is the evidence-based first-line treatment. Ask your healthcare provider for a reference for a sleep study if they suspect sleep apnoea.

Practice Pacing

Pacing is a structured energy management strategy recommended for long COVID, fibromyalgia, and post-viral fatigue. The goal of pacing is to minimize post-exertional worsening — the crash that follows exertion, rather than eliminate activity entirely. People who pace well are active when able and rest when tired.

Pacing applies to both physical and cognitive activity. Mental effort, like reading, screen time, conversations, and decision-making, uses energy just as physical activity does.

A practical stepwise approach:

1. Track your baseline energy — for one week, note what activities you did, how long they took, and how you felt during and afterward. This gives a baseline of your current energy levels.
2. Identify your energy envelope — the level of activity you can sustain without triggering a worsening of symptoms. Stay within it, even on good days.
3. Break tasks into smaller parts — rather than completing a task in one sitting, divide it into segments with planned rest periods in between.
4. Plan rest proactively — rest before fatigue sets in, not only after. Scheduled rest is more protective than reactive rest.
5. Resist the boom-and-bust cycle — doing too much on a good day followed by a crash on a bad day is the most common pacing error. Consistency matters more than output on any single day.
6. Expand activity gradually and slowly — only increase activity levels when a stable baseline has been maintained for at least two weeks without symptom worsening.

Many people with Long COVID and fibromyalgia find pacing as one of the most important ways to manage their condition.

Complete an Elimination Diet Protocol

Sensitivity to certain foods can cause brain fog. It is best to work with a healthcare provider who is trained in elimination diets.

Remove the most common food triggers — gluten, dairy, soy, corn, sugar, processed food, grains, alcohol, and caffeine. Eliminate the suspect foods for two weeks, then reintroduce one at a time.

Review Alcohol and Cannabis Use

A four to six-week period of reduction or elimination is the most practical way to assess whether either is contributing to brain fog and disrupted sleep.

What Supplements May Help With Brain Fog?

There is no single supplement that resolves brain fog. It is best to work with a healthcare practitioner who is trained in therapeutic supplementation.

Omega-3 fatty acids (EPA and DHA)

A low omega-3 index has been associated with cognitive impairment in older adults (Lukaschek et al., 2016). However, the evidence base is not uniformly consistent — some trials used low doses, others did not measure blood levels before or after supplementation. Measuring the omega-3 index before supplementing and retesting after three to four months provides meaningful clinical information.

Many people do not take an adequate dose of omega-3s unless they get tested.

Vitamin D

Vitamin D insufficiency has been associated with cognitive impairment, and a 12-month randomized controlled trial found that supplementation improved cognitive function in older adults with mild cognitive impairment by reducing oxidative stress (Yang et al., 2020). Testing before supplementing is important.

Read about How Much Vitamin D Should You Take

Iron

Where iron deficiency is confirmed by laboratory testing, correction can normalize cognitive performance (Murray-Kolb & Beard, 2007).

Coenzyme Q10 (CoQ10)

CoQ10 plays a central role in mitochondrial energy production. There is a sound theoretical basis for its use in conditions involving cellular energy impairment. Higher doses of 200-300 mg a day may be necessary to get a good response. CoQ10 levels can be measured in specialized labs.

Brain fog has many possible causes; identifying the right cause for each person is what makes treatment effective. It is important to rule out major underlying conditions first, and it is best to work with a knowledgeable healthcare provider.

References

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