Why You’re Always Tired: The Science Behind Brain Fog and Fatigue (And How to Beat It!)

If you feel like your brain’s in a cloud and you just can’t shake the tiredness, no matter how much you sleep or how many cups of coffee you down, you’re not alone. What's more, it’s not all in your head.

Brain fog and fatigue can be more than everyday stress catching up with you. They could be signals that your body and brain are out of sync in a much deeper way. The good news?

There are science‑backed ways to reclaim your energy and clarity — and you can start today.

Key Takeaways

• Brain fog and fatigue are closely linked, often amplifying each other and making cognitive tasks feel nearly impossible.

• There’s no medical test for brain fog, but common symptoms include memory lapses, trouble focusing, and overwhelming tiredness.

• Natural solutions like proper nutrition, better sleep hygiene, stress management, and brain‑boosting supplements can significantly improve mental clarity and energy levels.

When Brain Fog and Fatigue Happen Together

Brain fog symptoms can become worse and more debilitating when combined with fatigue. It can turn mild brain fog into severe brain fog. And this cognitive impairment can come with symptoms that are strikingly similar to other conditions that trigger cognitive dysfunction, such as:

• Traumatic brain injury (TBI)

• Chronic fatigue syndrome (CFS)

• Sleep apnea

• Fibromyalgia (fibro fog)

• Celiac disease

• Long COVID

• Hypothyroidism and other hormonal changes

• Cancer treatment ("chemo brain")

• Mental health conditions including anxiety and depression

• Hormone changes

Fatigue and brain fog are often co‑occurring conditions. Central fatigue refers to a person's challenges with mental tasks, whereas peripheral fatigue refers to muscle impairment or exhaustion stemming from physical effort, such as running a marathon.

Because fatigue and brain fog so often occur together and are difficult to define (and therefore to treat), the Centers for Disease Control (CDC) puts brain fog and fatigue in the same camp as traumatic brain injuries, due to their common link to fatigue and altered cognition (FAC). ¹

Especially with regards to long COVID, many patients complain that their brain fog is a major limiter of activities of daily living. And some have severe enough cognitive difficulties that they have to quit work or take a leave of absence.

Symptoms: How to Recognize Brain Fog and Fatigue

There's no exact medical definition of brain fog. Rather, it's a colloquial cluster of symptoms that can really take a toll on daily functioning, including:

• Memory problems, especially immediate memory.

• Trouble finding the right words in conversation.

• Feeling overwhelmed by simple everyday tasks.

• Problems with paying attention.

• Speed of processing information.

• Challenges with executive function, such as planning, organizing, and multi‑tasking.

• Forgetfulness.

• Lack of focus.

• Fatigue, tiredness, and low energy.

These symptoms can lead young people to have trouble concentrating in classes or while doing homework assignments or taking exams. They might have an idea, and then immediately forget it. And the troubles can spill over into relationships, making it hard to make friends and socialize.

It can also affect their physical performance and promote poor motor function—for example, in sports, or behind the wheel of a vehicle (especially for young, inexperienced drivers).

For professionals, it can lead to many of the same problems, only applied to their work, commute, and social environments instead of school.

Chronic brain fog and fatigue is defined as long‑term and ongoing. Some people may have shorter bouts of both.

What's the Cause?

Scientists don't yet know exactly what causes brain fog, despite the fact that it's been a known “thing” since 1850, when British physician James Tunstall mentioned it in relation to mental exhaustion experienced by “brainworkers” such as attorneys, teachers, and students.

We do know that a number of issues can trigger or exacerbate brain fog:

• Sleep deficiencies, poor sleep quality, and sleep apnea. Can also weaken your immune system, decrease red blood cells, make you irritable, and lower your reaction time.

• Nutritional deficiencies (especially B vitamins and B12, magnesium, omega-3)

• Diabetes and low blood sugar

• Hormonal changes including menopause and thyroid

• Inflammation. Inflammation produces free radicals which attack mitochondrial membranes, impairing their function.

• Underlying health conditions including multiple sclerosis, systemic lupus erythematosus, and others. Often linked to inflammation and poor concentration.

• Chronic stress and burnout. Stress can cause sleep disorders, which can lead to fatigue and make brain fog worse. A study also suggests that stress leads to changes in the hippocampus, the area of the brain responsible for memory and learning. [3]

• Long COVID.

• Certain medications such as chemotherapy (chemo brain fog).

As previously mentioned, long COVID patients can have a rough time with brain fog. And unfortunately, it's somewhat subjective, as there are no lab tests to confirm a diagnosis. Still, 7% of adults -- 17 million people -- experience long COVID, according to a Yale University publication. Patients say that their brain feels like a bad Wi-fi connection trying to load a large video... it just doesn't work like it should.

One theory about why long COVID continues to affect patients long after the acute infection is that it continues to live on in the gut after the initial infection clears. And there's a strong gut-to-brain connection.

Unfortunately, there's no single medical test to diagnose long covid. Nor is there a specific cognitive screening test. Doctors often evaluate it in the context of related issues including fatigue, sluggish thinking, and memory difficulties.

While long covid usually resolves on its own (eventually), the interim can be debilitating. Fortunately, there are coping strategies you can use, so keep reading.

The Brain‑Body Connection: How Fatigue Impacts Mental Clarity

What is fatigue, anyway? Drowsiness is a desire to sleep, like what most people experience in the evening. Fatigue is more general and far-reaching. It can last for days or weeks with no relief. And it can engulf both physical and mental challenges.

Your brain only comprises about 2% of your total body weight, but it consumes about 20% of your body's total energy. This colossal energy demand hints at why mental fog and fatigue are typically among the first symptoms people notice when something throws the body's energy systems out of whack.

Mitochondria are the powerhouses of every cell. Think of them as "small but mighty mitochondria."

The mitochondria produce Adenosine Triphosphate (ATP) -- the primary molecule used for all that cellular energy, including the energy your brain needs to carry out tasks from focused thinking to basic cognitive processes. You want your mitochondria working at peak levels to keep your energy up.

When the mitochondria don't function properly, energy output drops, and your brain suffers. Then you get mental fatigue, brain sluggishness, and difficulty focusing, among other things.

Everyday Habits That Worsen Brain Fog and Fatigue

Many people mistakingly worsen their brain fog and fatigue with less than optimal lifestyle habits, such as:

• Diets high in processed foods and sugar. Empty calories can promote brain fog because you're not giving your brain the key nutrients it needs to support your central nervous system. So it's not surprising that you'll have difficulty concentrating, and symptoms of brain fog.

• Sedentary lifestyles. Exercise promotes blood flow to the brain, and supports strong brain health and cognitive performance. If you have any cognitive challenges, exercise is just what the doctor ordered to improve brain function.

• Poor sleep hygiene can be an underlying cause of fatigue-related mental fog. If you have a sleep disorder such as sleep apnea, you may not even realize how detrimental it is to your brain health.

• Excess screen time and poor "digital hygiene." The National Sleep Foundation has found that screens emit blue light, disrupting your ability to fall asleep by suppressing melatonin production. Screens also reduce your slow-wave and REM sleep, which are critical for cognitive function. [2]

• Too much caffeine and other stimulants. Caffeine, especially after noon, can dampen your ability to fall asleep and stay asleep, and can therefore lead to sleepless nights, brain fog, and fatigue. 

Simple Steps to Clear Brain Fog and Boost Energy

Fortunately there are some fairly simple steps you can take to clear brain fog and boost energy.

• Hydration. Dehydration can cause brain fog and fatigue because your body and brain don't have enough fluids for proper function. This can lead to low energy and brain fog. Could something as simple as drinking more water improve symptoms? Absolutely. Start carrying a glass or steel water bottle with you and track how much you're drinking.

• Eat an anti-inflammatory diet with brain-boosting nutrients to boost healthy cells. A diet that's high in sugar, processed foods, and unhealthy fats can lead to fatigue and brain fog. Instead, eat a healthy diet with whole foods including vegetables and fruits, nuts and seeds, quality proteins such as chicken, fatty fish, eggs, and grass-fed beef. Enjoy healthy fats such as coconut oil, olive oil, and real butter.

• Regular physical activity. Skimping on exercise is a recipe for mood disorders, fatigue, and it can make you develop brain fog. Plus, you'll sleep better with more exercise during the day. You may even notice brain fog disappears with exercise. So pull that bike out of your garage, take walks, join and use a club, take up a new sport, work with a trainer. You're sure to like the results. Why not test this out for a month?

• Improve your sleep hygiene. Sleep can affect cognitive function in a major way. During deep sleep, your brain cleans out toxic proteins, consolidates memories and learning, and repairs cellular damage. Establish a consistent bedtime and wake-up time, even on weekends. Sleep in a completely dark and cool room. Avoid screens, alcohol, and big meals within two hours of bedtime. Also, exercise earlier during the day, and get out in the sunshine at midday.

• Get sunshine. Fifteen minutes in the sunshine at midday can do wonders for your mood, your mitochondrial health, and your vitamin D levels (assuming exposed skin).

Stress Management: Mental Clarity Through Relaxation

Stress releases an outsized portion of the hormone, cortisol, which can cross the blood brain barrier, and land on receptors related to memory, learning, and executive function. Cortisol is great in small amounts, but can do untold damage when there's too much.

Improving cognitive symptoms can be accomplished by better managing stress and its cortisol effect. As mentioned, chronic stress can damage the hippocampus and trigger fatigue and brain fog. It can also raise your blood pressure, potentially cause long-term mental decline, and create other symptoms.

Embrace the benefits you can enjoy from mindfulness, yoga, and meditation. General exercise is a known stress buster and also reduces inflammation.

Breathing plays a key role in regulating our mental state and our nervous system. During times of stress, breathing becomes shallow and fast, activating the "fight or flight" response. This in turn increases your heart rate, blood pressure, and muscle tension.

Slow, deep breathing, on the other hand, stimulates the parasympathetic nervous system, promotes relaxation, and reduces stress... making it a powerful way to control stress. 

Supplements for Brain Fog

Certain nutrients are needed in abundance to support all those major energy needs of your brain and nerve cells and overall body function.

A group of over the counter supplements called nootropics (so-called "smart" supplements) offer great potential benefits for mental clarity and energy. Sure, you can also use memory aids and talk therapy to help. But why not address your brain's underlying nutritional needs first?

Think of your brain as a garden that needs the right nutrients to flourish. A healthy diet is important. But certain supplements show a remarkable ability to boost cognition and roll away those clouds that fog your thinking.

Some of the most critical nutrients for your brain include: 

• Omega-3 fatty acids. Studies show that taking EPA and DHA omega-3 fatty acids may support memory, attention, and mood. Omega-3s improve symptoms of brain fog by boosting mood and reducing anxiety. [8] Omega-3s are included in Green Valley's Brain Vitality Plus supplement -- a great way to boost your brain with several key ingredients in one simple swallow.

• B vitamins. Studies show that insufficiencies of various B vitamins can cause brain fog and fatigue. B vitamins are often referred to as energy vitamins. A study of 39,000 people showed that low B12 levels were associated with memory problems and poor attention. [6] A much smaller study names B12 deficiency as an "underestimated cause of minimal cognitive impairment and dementia." [7] If you are a vegetarian or vegan, you're quite likely to be in sufficient in B12, as it is found in animal meats.

• Vitamin D. Vitamin D3 receptors are widespread in the brain tissue and the nervous system. D3 has shown neuro-protective benefits including clearing of amyloid plaques. [4] It controls neurotransmitters and their signals. Holistic physicians recommend your level of vitamin D stay between 50 and 70.

• Magnesium. Low magnesium levels are common in those who are stressed, and low levels trigger brain fog and fatigue. A study of 2,466 adults over age 60 showed that those with the highest magnesium levels showed the best cognitive function. [5]

• Adaptogenic herbs. From boosting blood vessel function to calming stress, adaptogenic herbs have been a cornerstone of Ayurvedic medicine for ages. Herbs to consider include Bacopa monnieri, Rhodiola rosea, ashwagandha, ginkgo biloba, and ginseng.

• Citicoline. Citicoline is a key building block of acetylcholine and phosphatidylcholine. Both are essential for brain health. Citicoline can address poor concentration and improve cognitive function, protect neurons, boost energy, and improve mood. It is a potent ingredient in Green Valley's Brain Vitality Plus supplement.

• Coffee Fruit Extract. Derived from the red fruit surrounding the part of the bean that gets roasted, it is bursting with antioxidants that can boost your brain and memory. Coffee fruit extract fights oxidative stress and inflammation, and is another stealth ingredient in Green Valley's Brain Vitality Plus.

If you experience brain fog or cognitive dysfunction, you owe it to yourself to implement these great strategies to send it packing. Doing so will improve brain function and improve your immune system, among other things.

Summary

Brain fog and fatigue are often misunderstood symptoms that can drastically impact daily life, from memory and focus to motivation and energy. Although they stem from various causes — including poor sleep, stress, long COVID, and nutritional deficiencies — there are proven, natural ways to manage and even reverse these symptoms. By focusing on lifestyle changes and targeted nutritional support, you can clear the fog and feel like yourself again.

Frequently Asked Questions

What causes brain fog and fatigue?

There are a number of causes of brain fog and fatigue -- including lack of sleep, underlying health conditions such as chronic fatigue syndrome, cancer treatment and other medications, traumatic brain injury, hormone changes, poor nutrition, and chronic stress. 

Why do I feel fuzzy in my head?

Feeling fuzzy in the head is another way to describe brain fog, including fatigue, memory problems, processing speed, and inability to focus. It can point to potential nutritional deficiencies, lack of exercise, and underlying conditions. 

What deficiency causes brain fog and fatigue?

Various nutrient deficiencies are linked to brain fog and fatigue. Key among them are deficiencies of vitamin D3, magnesium, B12 and other B vitamins, omega-3 fatty acids, and citicoline.

What vitamin clears brain fog?

Vitamins that can help clear brain fog include vitamin B12, other B vitamins, vitamin D3, magnesium, omega-3 fatty acid, and citicoline. 

When should I be worried about brain fog?

If your brain fog persists for weeks or months and is highly disruptive to your daily activities and routine, you should consult a healthcare provider and have them help you figure out what's causing your symptoms. Especially if you've tried the lifestyle strategies and supplements listed above, and still haven't seen resolution of your symptoms.