You walk into a room and forget why you went there.

You lose your train of thought in the middle of a sentence.

You know the word you want to say, but you cannot seem to find it.

You reread the same paragraph three times and still cannot remember what you just read.

You feel mentally slow, distracted, forgetful, or simply not as sharp as you used to be.

Many people describe this feeling with two words:

Brain fog.

Brain fog is not a medical diagnosis. It is a term people use to describe changes in thinking, memory, concentration, mental clarity, and processing speed.

At O'Keefe Matz Functional Health Clinic in St. Paul, Minnesota, we often hear people say:

"I just don't feel as sharp as I used to."

Or:

"I feel like my brain isn't working right."

The question is not simply whether you have brain fog.

The more important question is:

Why?

Here are 17 possible causes of brain fog that are often overlooked.

1. Your Thyroid May Not Be Functioning Optimally

Thyroid hormones influence metabolism throughout the body, including the brain.

When thyroid function is low, some people experience difficulty concentrating, slower thinking, forgetfulness, fatigue, and depression.

You may also notice:

Cold hands and feet

Constipation

Weight gain or difficulty losing weight

Dry skin

Hair thinning

Muscle weakness

Elevated cholesterol

Fatigue

Many people have had a TSH test and were told their thyroid was "normal."

However, TSH is only one part of thyroid evaluation.

Depending on symptoms and health history, a more comprehensive thyroid evaluation may include TSH, free T3, free T4, thyroid peroxidase antibodies, and thyroglobulin antibodies.

This may be particularly important when evaluating for Hashimoto's thyroiditis.

2. Hashimoto's May Be Affecting More Than Your Thyroid

Hashimoto's thyroiditis is an autoimmune condition in which the immune system targets the thyroid.

People often associate Hashimoto's with weight gain and fatigue.

But many patients also describe significant changes in mental clarity.

They may experience:

Brain fog

Forgetfulness

Difficulty concentrating

Mental fatigue

Slower processing

Difficulty finding words

Mood changes

Because Hashimoto's is an autoimmune condition, evaluating the bigger picture may be important.

This can include thyroid function, inflammation, gastrointestinal health, nutrient status, blood sugar regulation, and other factors that may influence immune function.

3. Your Blood Sugar May Be Swinging Throughout the Day

Your brain requires a steady supply of energy.

When blood sugar rises and falls dramatically, some people experience changes in mental clarity.

You may feel sharp after eating and then mentally exhausted a few hours later.

Or you may notice:

Difficulty concentrating when hungry

Irritability

Shakiness

Sugar cravings

Afternoon fatigue

Headaches

Feeling better immediately after eating

Needing caffeine to concentrate

Fasting glucose may appear normal even when blood sugar regulation is beginning to change.

Depending on the person, fasting insulin and hemoglobin A1c may provide additional information.

4. You May Have Insulin Resistance

Insulin resistance can develop years before someone is diagnosed with diabetes.

The body may produce increasing amounts of insulin to keep blood glucose within the standard range.

During this time, a person may be told their glucose is normal.

However, elevated insulin and metabolic dysfunction may already be present.

Insulin resistance has been associated with inflammation and changes in brain health.

People may also experience fatigue, carbohydrate cravings, difficulty losing weight, abdominal weight gain, and mental fogginess.

5. Menopause and Perimenopause Can Affect the Brain

Many women are surprised by how significantly perimenopause and menopause can affect their thinking.

They may say:

"I feel like I'm losing my mind."

They forget appointments.

They struggle to find words.

They walk into rooms and forget why they are there.

They feel distracted and mentally overwhelmed.

Changes in estrogen and progesterone can influence sleep, mood, neurotransmitter activity, and cognitive function.

At the same time, menopause may overlap with thyroid problems, insulin resistance, poor sleep, chronic stress, and nutrient deficiencies.

Brain fog during menopause should not automatically be dismissed as "just getting older."

6. Low Iron or Ferritin May Affect Mental Energy

Iron is important for oxygen transport and many biological processes.

Ferritin reflects stored iron.

You do not necessarily have to be anemic to have low iron stores.

Some people with low or suboptimal ferritin describe:

Mental fatigue

Difficulty concentrating

Poor exercise tolerance

Headaches

Restless legs

Hair loss

Feeling cold

Physical exhaustion

A complete iron evaluation may include serum iron, ferritin, total iron-binding capacity, and iron saturation.

7. Vitamin B12 or Folate May Be Low

Vitamin B12 and folate are important for neurological function.

Low levels may contribute to:

Brain fog

Memory changes

Fatigue

Numbness or tingling

Balance problems

Mood changes

Weakness

Some people have difficulty absorbing B12 because of gastrointestinal problems, medications, autoimmune conditions, or changes in stomach acid.

The question is not only whether you are consuming enough B12.

The question may also be whether you are absorbing and utilizing it appropriately.

8. Poor Sleep May Be Affecting Your Brain

Your brain performs important restorative processes while you sleep.

Sleep is involved in memory consolidation, learning, emotional regulation, and brain recovery.

You may be sleeping seven or eight hours but still not getting restorative sleep.

Frequent waking, pain, stress, alcohol, hormonal changes, blood sugar fluctuations, and breathing problems may interfere with sleep quality.

If you wake up exhausted and mentally foggy, sleep quality deserves a closer look.

9. Sleep Apnea May Be Disrupting Your Brain Function

Sleep apnea causes repeated interruptions in breathing during sleep.

You may not remember waking up.

However, your brain may repeatedly move out of deeper stages of sleep throughout the night.

Possible symptoms include:

Morning headaches

Dry mouth

Snoring

Daytime fatigue

Brain fog

Memory problems

Difficulty concentrating

Falling asleep while watching television

High blood pressure

Sleep apnea can affect people of many different body types.

It should not automatically be ruled out simply because someone is not overweight.

10. Chronic Stress May Be Overloading Your Brain

The brain is not designed to process an endless stream of stress without consequences.

Work.

Family.

Finances.

Caregiving.

Health concerns.

Constant notifications.

Emails.

News.

Social media.

When your nervous system remains on alert for long periods of time, concentrating on nonurgent information may become more difficult.

You may become forgetful.

You may lose words.

You may have difficulty organizing your thoughts.

You may feel mentally exhausted by simple decisions.

Sometimes brain fog is not a lack of intelligence or motivation.

Your brain may simply be overwhelmed.

11. Your Cortisol Rhythm May Be Disrupted

Cortisol plays an important role in the body's stress response and daily wake-sleep cycle.

Ideally, cortisol follows a predictable rhythm.

It should rise in the morning and gradually decrease throughout the day.

When this rhythm becomes disrupted, people may describe feeling:

Exhausted in the morning

Foggy during the day

Dependent on caffeine

Mentally tired in the afternoon

Wired at night

Unable to fall asleep

Awake between 2:00 and 4:00 a.m.

Evaluating cortisol at multiple points throughout the day may sometimes provide more information than a single morning cortisol measurement.

12. Chronic Inflammation May Be Affecting Your Brain

Inflammation does not only affect joints and muscles.

Inflammatory processes can also influence how people feel mentally and emotionally.

People experiencing chronic inflammation may describe:

Mental fogginess

Fatigue

Low motivation

Difficulty concentrating

Slower thinking

Feeling physically and mentally drained

Inflammation may be associated with autoimmune disease, metabolic dysfunction, poor sleep, gastrointestinal problems, chronic stress, infections, and environmental exposures.

High-sensitivity C-reactive protein is one marker that may be considered when evaluating inflammation.

13. Your Gut May Be Affecting Your Brain

The gut and brain communicate constantly.

This is sometimes referred to as the gut-brain axis.

The gastrointestinal system plays an important role in nutrient absorption, immune regulation, inflammation, and signaling between the digestive system and the brain.

If you have brain fog along with:

Bloating

Constipation

Diarrhea

Reflux

Abdominal discomfort

Food reactions

Excessive gas

Changes in bowel movements

It may be worth evaluating gastrointestinal health.

Depending on symptoms and history, conditions such as small intestinal bacterial overgrowth, intestinal inflammation, digestive insufficiency, or altered gut bacteria may be considered.

14. You May Not Be Absorbing the Nutrients Your Brain Needs

Eating a healthy diet does not always guarantee that nutrients are being absorbed properly.

Low stomach acid, gastrointestinal inflammation, celiac disease, digestive enzyme problems, and bacterial overgrowth may interfere with nutrient absorption.

Iron, B12, folate, magnesium, and other nutrients are important for neurological function and energy production.

Sometimes the problem is not what you eat.

The problem may be what your body is able to absorb.

15. Medications May Be Contributing to Mental Fog

Brain fog and cognitive slowing can be side effects of some medications.

These may include certain:

Antihistamines

Sleep medications

Anti-anxiety medications

Antidepressants

Pain medications

Muscle relaxants

Blood pressure medications

Medications should never be stopped without speaking with the prescribing provider.

However, if brain fog began after starting or changing a medication, it may be worth discussing with your healthcare team.

16. Your Brain May Still Be Recovering From an Illness or Injury

Some people notice significant changes in mental clarity after a viral illness, prolonged infection, concussion, or other physical stressor.

They may say:

"My brain has never felt the same since."

Symptoms may include:

Slower processing

Difficulty concentrating

Mental fatigue

Headaches

Word-finding problems

Memory changes

Sleep disruption

Sensitivity to light or sound

Feeling overwhelmed in busy environments

When symptoms begin after an illness or head injury, the timeline matters.

This is one reason a detailed health history is so important.

17. There May Be More Than One Cause

This is probably one of the most important things to understand about brain fog.

You may be in menopause and have thyroid dysfunction.

You may have low ferritin and poor sleep.

You may have insulin resistance and chronic stress.

You may have gastrointestinal dysfunction and low B12.

You may have a history of concussion and significant sleep disruption.

The brain does not operate separately from the rest of the body.

Your thyroid affects your metabolism.

Your gut communicates with your brain.

Your hormones influence sleep and neurotransmitter activity.

Your blood sugar affects energy availability.

Your nervous system responds to stress.

Your immune system influences inflammation.

This is why persistent brain fog often requires looking at the entire pattern.

"My Blood Tests Are Normal, So Why Can't I Think Clearly?"

This is a question we hear frequently.

Someone knows their thinking has changed.

They feel slower.

They are forgetting things.

They cannot concentrate.

They struggle to find words.

Basic laboratory testing is performed.

Then they receive a message:

"Everything looks normal."

But they still do not feel normal.

Basic laboratory testing provides important health information.

However, depending on the person's symptoms and history, additional evaluation may be appropriate.

This might include looking more closely at:

Thyroid function and thyroid antibodies

Iron and ferritin

Vitamin B12 and folate

Vitamin D

Fasting insulin

Hemoglobin A1c

Inflammatory markers

Hormone patterns

Cortisol rhythm

Gastrointestinal function

Nutrient status

The goal is not to order every laboratory test available.

The goal is to understand the person sitting in front of us and ask better questions.

When Should Brain Function Be Evaluated More Directly?

Sometimes laboratory testing and functional medicine evaluation are only part of the picture.

If brain fog is accompanied by problems with concentration, processing speed, memory, sleep, headaches, anxiety, nervous system regulation, or a history of concussion, evaluating brain function more directly may also be considered.

At O'Keefe Matz Functional Health Clinic, we use quantitative EEG, commonly called QEEG brain mapping, to evaluate patterns of electrical activity in the brain.

A QEEG does not diagnose the cause of every cognitive symptom.

However, it may provide additional information about patterns of brain activity associated with regulation, attention, processing, sleep, and other neurological functions.

When appropriate, this information may help guide individualized brain-based therapies such as neurofeedback or photobiomodulation, also known as red light therapy for the brain.

The important point is that brain fog can have many different causes.

Sometimes the problem begins in the body.

Sometimes brain function itself deserves a closer look.

And sometimes both need to be evaluated.

A Functional Medicine Approach to Brain Fog in St. Paul, Minnesota

At O'Keefe Matz Functional Health Clinic, Dr. Shannon O'Keefe works with patients experiencing brain fog, fatigue, thyroid symptoms, Hashimoto's, menopause, digestive problems, and other complex health concerns.

Dr. O'Keefe is a chiropractic physician and Board Certified Clinical Nutritionist with decades of experience in healthcare and clinical nutrition.

Her approach is scientific, thorough, and individualized.

Instead of simply asking:

"How do we treat brain fog?"

She asks:

"Why is this person's brain foggy?"

That may involve evaluating thyroid function, thyroid antibodies, insulin and glucose regulation, iron and ferritin, nutrient status, inflammation, hormone changes, cortisol patterns, gastrointestinal health, sleep, and other factors that may be influencing brain function.

Many patients with brain fog have been told their laboratory tests are normal.

They know something has changed.

They simply have not found an explanation yet.

Functional medicine provides a way to look more closely at patterns and possible contributing factors.

Is It Brain Fog or Is Something Else Going On?

Occasionally forgetting where you put your keys happens to everyone.

But persistent changes in memory, concentration, processing, or mental clarity deserve attention.

Especially when you find yourself saying:

"This isn't normal for me."

You know your brain.

You know how you used to think.

You know when something has changed.

The goal is not to assume the worst.

The goal is to ask better questions.

Are You Tired of Feeling Mentally Foggy?

If you are struggling to concentrate, forgetting words, losing your train of thought, or feeling like your brain is moving through mud, it may be time to look deeper.

Dr. Shannon O'Keefe offers a complimentary 15-minute phone consultation to discuss your symptoms, health history, and whether a functional medicine approach may be appropriate for you.

O'Keefe Matz Functional Health Clinic is located in St. Paul, Minnesota and works with patients seeking a more comprehensive approach to brain fog, fatigue, thyroid concerns, Hashimoto's, menopause, digestive problems, and chronic health symptoms.

For patients with concerns involving brain function, concentration, processing, sleep, concussion history, or nervous system regulation, QEEG brain mapping and brain-based therapies may also be considered when appropriate.

Brain fog is a symptom.

The question is: what is your brain trying to tell you?