What are causes of fatigue

18 Causes of Fatigue and How to Find More Energy

Dr. Jolene BrightenPublished: Last Reviewed: Wellbeing Leave a Comment

Do you wish you had more energy than you currently do? You're not alone. Fatigue is one of the most common complaints that bring patients into my office. In fact, it's estimated that about 20% of all doctor visits are related to fatigue. In this article, I'll help you understand what are the causes of fatigue and how to find more energy naturally.

Low energy, as well as related symptoms like lethargy and trouble focusing, can stem from a wide range of causes, including nutrient deficiencies in B12 and iron, chronic stress, an underactive thyroid, ADHD, and many others.

I often find that if my patients work on improving their diets, gut health, hormonal balance, and detoxification, then they feel a lot more revitalized and energetic as a result.

Below, I share how I approach fatigue and give tips to help you increase your energy levels. I also explain common causes of low energy, which can include:

  • Nutrient deficiencies
  • Getting less than 7-9 hours of sleep each night
  • Eating a restrictive diet
  • HPA axis dysregulation (aka adrenal fatigue, often tied to stress)
  • Poor thyroid function
  • Autoimmune disorders
  • And others

18 Common Causes of Fatigue

According to recent surveys, about 30% of adults report experiencing fatigue on a regular basis that affects their daily activities, while over 40% of adults report feeling tired or low on energy three or more days per week.

From hectic, stressful lifestyles and poor sleep habits to nutritional deficiencies tied to dieting, there are numerous culprits behind low energy levels. Understanding these common causes can help you to pinpoint the root cause of your exhaustion and take steps to address it effectively.

Fatigue and tiredness symptoms:

  • Chronic or extreme tiredness and lack of energy
  • Headaches
  • Poor decision making and judgment
  • Impaired reaction time or reflexes
  • Muscle weakness
  • Joint and muscle pain
  • Weight gain
  • Flu-like symptoms
  • Irritability, moodiness

Here's more about the most common causes of low energy:

1. Sleep Deprivation

Between 64% and 75% of adults say they get less than eight hours of sleep most nights of the week, while about 30% consistently get less than the minimum healthy amount, which is seven hours.

Conditions like insomnia, sleep apnea, restless legs syndrome, and circadian rhythm disorders can significantly impact sleep quality, leading to daytime fatigue.

Ensuring you get adequate sleep every night — which is between seven to nine hours for most adults —can significantly boost your energy levels, especially if you're dealing with other stressors and causes of fatigue.

Related: 10 Best Sleep Supplements That Aren't Melatonin

2. Nutrient Deficiencies

Nutrient deficiencies, particularly in B12 and iron, are frequent causes of low energy.

  • B12 deficiency: B12 plays a crucial role in energy production. A deficiency in this vitamin can lead to a significant drop in energy levels. While blood tests can measure B12, further testing is often required to ensure its bioavailability in the body.
  • Iron deficiency: Iron is essential for hemoglobin, the protein responsible for oxygen transport in the blood. Insufficient iron levels can impair oxygen delivery to tissues, causing fatigue and decreased exercise tolerance.

For both B12 and iron to be adequately absorbed, you need to have an optimally functioning gut with the right amount of stomach acid. These can be difficult if you're dealing with poor gut health, such as due to hypothyroidism, inflammatory bowel disease, or simply older age.

Beyond specific nutrient deficiencies, overall poor nutrition and erratic eating patterns that lack balance can contribute to fatigue. For example, not eating enough carbohydrates and protein can make some people lethargic.

3. Poor Gut Health and Energy Levels

Suboptimal gut health can increase inflammation and hinder nutrient absorption, leading to low nutrient levels and fatigue, sometimes in the form of chronic fatigue syndrome.

Issues like bacterial imbalances, candida overgrowth, SIBO, leaky gut, or infections can all contribute to gut dysfunction and drain your energy. Celiac disease, an autoimmune disease triggered by gluten, or inflammatory bowel disease can also lead to nutrient deficiencies, gut inflammation, and can be a cause of exhaustion.

Poor immune function and hormonal dysregulation in response to gut inflammation and oxidative stress are also causes of fatigue.

I often recommend functional gastrointestinal testing to my patients to identify and address underlying gut issues, which can sometimes persist without noticeable digestive symptoms. I also refer to a gastroenterologist if the patient has symptoms of lab markers suggesting conditions such as celiac disease, crohn's disease, ulcerative colitis, or other serious gut conditions.

Ask yourself if you experience any of these symptoms in addition to low energy, which might indicate poor gut health:

  • Bloating and gas
  • Stomach pains
  • Heartburn/ GERD
  • Constipation
  • Diarrhea
  • Irritable bowel syndrome (IBS) symptoms
  • Nausea
  • Cramps
  • Joint Pain
  • Changes in appetite
  • Weight Loss

If you're experiencing any of these, it is important to communicate with your physician or medical care team.

4. Chronic Stress and Mental Health Issues

Chronic stress can lead to what many people refer to as “adrenal fatigue,” which more accurately describes HPA axis dysregulation. This occurs when the body's response to ongoing stressors results in a depletion of energy reserves and a constant feeling of being tired.

Depression, anxiety, and other mental health disorders often have fatigue as a major symptom. Emotional exhaustion can manifest as physical tiredness, irritability, poor concentration, and general “brain fog.”

Allostatic load refers to the cumulative effect of life stressors. In some cases, the allostatic load can exceed what the neuroendocrine response (aka the HPA axis response) is capable of managing. Examples of stressors that contribute to allostatic load and exhaustion include:

  • Poor sleep and circadian disruption
  • Smoking
  • Alcohol consumption
  • Lack of exercise
  • Low-nutrient or unhealthy diet
  • Subtle and chronic stressors that elicit an HPA axis response
  • Major life events (death, divorce, etc.)
  • Inability to reduce or turn off stress response when stress is no longer present
  • Discrimination, including racism and weight

5. Hormonal Imbalances

Hormonal changes that occur during periods of life like menopause and pregnancy can cause low energy. For example, a common menopause symptom is fatigue, in addition to hot flashes and night sweats.

Dysfunction in the adrenal glands and thyroid, also called “adrenal fatigue” or hypothyroidism, can significantly affect energy levels. These glands help to regulate hormonal production and maintain a healthy metabolism, so if they aren't working properly, low energy and mood-related issues are commonly experienced.

During times of heightened stress or when someone is experiencing HPA axis dysfunction, the normal cortisol rhythm can be disrupted, making someone feel “wired but tired” or unusually depleted. The key determinants of HPA axis regulation include:

  • Genetic background
  • Early life environment
  • Post-traumatic stress disorder (PTSD)
  • Current life stress and habits (including diet, exercise, and sleep patterns)

Insulin resistance (IR) and poor blood sugar management, which can be common with polycystic ovarian syndrome (PCOS) can also be a cause of exhaustion.

6. Exposure to Environmental Toxins

Exposure to environmental toxins, including molds and heavy metals, can sometimes lead to fatigue. If you suspect you have toxins from molds or heavy metals, I recommend being tested and treated appropriately.

Endocrine disruptors, synthetic chemicals found ubiquitously in the environment in household and beauty products, can also contribute to hormonal issues that might cause low energy.

If you are drinking or eating out of plastic containers, then I urge you to stop. Plastics have hormone-disrupting properties and add additional burden to the body. Choose filtered drinking water and buy organic foods whenever possible. Cook with pots and pans made from safer materials like cast iron, ceramic, and glass.

Related: How Endocrine Disruptors Cause a Hormone Imbalance

7. Infections

Infections and chronic diseases like reactivated Epstein-Barr virus, Lyme disease, and SIBO can weaken the immune system and cause fatigue. Early testing and treatment are essential to prevent energy depletion.

How do you know if you might have one of these conditions? Look out for symptoms like:

  • Bloating (sometimes which is severe) and indigestion
  • Muscle weakness
  • Joint pain
  • Feeling tired even after getting enough sleep
  • Headaches
  • Night sweats
  • Poor appetite
  • Fever
  • Swollen lymph nodes
  • Neck stiffness
  • Bell's palsy (facial drooping)
  • Heart palpitations
  • Dizziness or shortness of breath
  • Memory problems or difficulty concentrating

8. Poor Blood Sugar Regulation

Poor blood sugar regulation, driven by high sugar and carbohydrate intake, can lead to energy fluctuations. Eliminating high glycemic foods, most processed foods, and added sugar from your diet while also incorporating protein into every meal can stabilize blood sugar levels.

Food sensitivities and allergies can also contribute to fatigue; identifying and eliminating problematic foods through an elimination diet or sensitivity testing is beneficial.

9. Lack of Physical Activity

Regular physical activity boosts stamina and energy over time, while a sedentary lifestyle can lead to decreased energy levels.

A lack of exercise can lead to decreased circulation and oxygen delivery to tissues, resulting in reduced energy levels. Additionally, physical activity helps release endorphins, which can boost mood and combat feelings of fatigue.

10. Overtraining

While a sedentary lifestyle is linked to low energy, conversely, so is excessive physical activity without adequate rest.

Over-training can contribute to HPA axis dysregulation, especially if you're also restricting your calorie intake or eating a diet that isn't balanced without enough macronutrients and micronutrients. When this persists, it can lead to overtraining syndrome, where fatigue, weakness, and brain fog are key symptoms.

11. Chronic Pain

Living with chronic pain conditions such as fibromyalgia, arthritis, or chronic back pain requires a significant amount of energy, leading to extreme fatigue.

Chronic pain can contribute to fatigue due to the constant strain it places on the body, leading to disrupted sleep patterns and decreased physical activity. Additionally, the stress and discomfort associated with persistent pain can contribute to feelings of exhaustion and mental fatigue, impacting overall energy levels.

12. Use of Some Medications

Certain medications, including some blood pressure medications, antihistamines, and psychiatric medications used to manage anxiety or depression, can have side effects that include fatigue. If you take medications and notice a change in your energy or mood, talk to your provider about alternatives.

13. Dehydration

Not drinking enough fluids can lead to dehydration, which significantly affects energy levels and overall functioning. This is especially risky if you're sick and losing fluids, very active, sweating a lot, or live in a climate that's dry and hot.

14. Heart and Lung Conditions

Diseases affecting the heart or lungs, such as heart failure, coronary artery disease, or chronic obstructive pulmonary disease (COPD), can lead to feelings of fatigue due to decreased oxygen supply to the body's tissues.

15. Autoimmune Diseases

Autoimmune conditions like lupus, rheumatoid arthritis, and multiple sclerosis can cause chronic fatigue as the body's immune system attacks its own tissues. Hashimoto's thyroiditis, a common type of hypothyroidism in which the body attacks the thyroid gland, is also a cause of low energy and brain fog.

16. Endocrine Disorders

Besides hypothyroidism, other endocrine disorders like diabetes and adrenal insufficiency (known as Addison's Disease) can cause fatigue due to the imbalance of hormones that regulate energy. Check for symptoms aside from fatigue such as:

  • Increased thirst and hunger
  • Frequent urination
  • Muscle weakness
  • Unexplained weight loss
  • Blurred vision
  • Slow-healing wounds
  • Tingling or numbness in hands or feet
  • Recurrent infections
  • Irritability
  • Dry, itchy skin
  • Low blood pressure
  • Nausea, vomiting, or diarrhea
  • Dizziness or lightheadedness
  • Salt cravings
  • Darkening of the skin (especially in creases of the hands, elbows, knees, and knuckles)
  • Hypoglycemia (low blood sugar)

17. Alcohol and Substance Use

Regular consumption of alcohol or misuse of drugs can significantly impact sleep quality and energy levels. These substances are known to disrupt gut health and increase inflammation, which can take a toll on the gut-brain axis, neurotransmitter production, and your overall mood.

18. ADHD, AuDHD, Autism Burnout

Attention deficit hyperactivity disorder (ADHD), autism, and the combination of autism and ADHD (AuDHD) are all strongly correlated with fatigue and extreme exhaustion.

ADHD individuals report higher levels of stress and fatigue compared to those who are not. Hyperactivity, sleep disturbance, lack of sleep, and anxiety account of some of the reasons those with ADHD report higher levels of fatigue.

Anywhere from 50-70% of autistic people also meet the criteria for ADHD, which is why the neurodivergent community created the term AuDHD. The same factors contributing to ADHD fatigue also apply in this situation. 

Autistic fatigue is a state of extreme sensory, mental, and physical exhaustion. In these cases, fatigue symptoms may initially present as heightened senses and an inability to continue to hide autistic traits, what is commonly referred to ask masking. 

Autistic and ADHD burnout looks different compared to neurotypical counterparts. 

It is important to work with a healthcare provider equipped to support you if you're struggling with unexplained fatigue and identify with either of these conditions. Accommodations, individualized coping tools, and holistic support is important in addressing these types of fatigue.

How to Find More Energy

As a Naturopathic Physician, I prioritize a holistic approach to helping my patients raise their energy levels, focusing on the person's overall health profile rather than isolated symptoms.

Through detailed history-taking and comprehensive lab testing, including functional assessments, we can pinpoint the root causes of fatigue and develop an effective treatment plan to help them feel more energized, upbeat, and motivated.

I suggest working with a license healthcare provider if you're experiencing ongoing excessive fatigue, so as to assess whether you may have an infection or underlying condition. Additionally, you can take the steps below to help increase your energy:

1. Get Enough Sleep

Make it a priority to get seven to nine hours of sleep each night. If you have trouble sleeping:

  • Stop using electronics two hours before bedtime
  • Create a bedtime routine that promotes relaxation 1-2 hours before bed
  • Avoid watching stimulating TV, reading the news, or activities that make you feel stressed
  • Create a bedroom that is dark and cool
  • Try sleep supplements like melatonin and ashwagandha
  • Avoid afternoon caffeine.
  • Avoid vigorous exercise within 3 hours of bed
  • Limit naps to 20 minutes
  • Turn off all light-emitting electronics or place electronics in a separate room
  • Shift your bedtime by 15 minutes each night until you reach your ideal bedtime

If you have ADHD, Autism, or both, then you may need to try different sleep strategies. For example, if you use stimulants, make sure they are taken early in the day, opposed to the afternoon when they can disrupt sleep. 

Instead of avoiding electronics before bed, you may need to “doom scroll” boring stuff with blue light blocking glasses to get your mind chatter to settle.

While some people benefit from a quiet room, you may find the buzzing of the electricity or ticking of a clock drives your brain wild. Try putting on white noise, sound bath music, or binaural beats as an alternative. 

2. Improve Your Diet and Boost Your Nutrient Intake

Ensure you're consuming enough protein each day, as well as micronutrients from foods like dark leafy greens, fruits, legumes, nuts, and seeds. Add more vitamin B12, iron, and vitamin C to your diet (which assists in nutrient absorption) from foods like:

  • Beef liver
  • Salmon, sardines, and tuna
  • Eggs
  • Cheese and milk
  • Poultry
  • Red meat (beef, lamb)
  • Seafood (especially shellfish like clams, oysters, and mussels)
  • Beans and lentils
  • Pumpkin seeds
  • Quinoa
  • Spinach and other leafy greens
  • Oranges and grapefruits
  • Kiwi
  • Strawberries
  • Bell peppers (especially red)
  • Broccoli
  • Brussels sprouts
  • Tomatoes
  • Spinach
  • Papaya

I've got a free recipe guide for you here to help you get creative in putting these foods into your routine.

Food sensitivities can also contribute to fatigue; identifying and eliminating problematic foods through an elimination diet or sensitivity testing is beneficial.

To help improve blood sugar balance, which is key for energy:

  • Limit or remove refined carbs and sugar
  • Eat protein and healthy fats with all meals
  • Start the day with 25-30 grams of protein
  • Incorporate fiber-rich foods into your meals
  • Avoid caffeine until after breakfast
  • Strength train regularly
  • Go for daily walks

For more help, grab my free recipe guide here to get started.

3. Practice Stress-Reduction Techniques

Stress plays a major role in HPA axis dysfunction, and it can interfere with sleep and even your diet choices.

Mindfulness practices like meditation, breathing exercises, yoga, time spent outdoors, socializing, reading, and journaling can positively impact your ability to cope with stress and encourage HPA axis regulation that helps lift your energy.

Here's an article all about strategies to reduce stress.

4. Supplement to Support Hormonal Balance

In addition to managing stress, optimizing blood sugar, and sleeping enough, a number of supplements can help support the HPA axis, hormone production, and energy levels, such as:

My Adrenal Support formula may help boost your energy and ability to cope with stress as it contains adaptogens like ashwagandha, holy basil, and Rhodiola, all of which support a healthy stress response. In addition to adaptogenic herbs, it provides B vitamins and vitamin C to support adrenal, hypothalamic, and pituitary (HPA axis) function, which controls hormone output and helps determine your energy levels.

5. Exercise Moderately

Considering that both too much and too little exercise can leave you feeling wiped out, strike a balance and find the middle path between extremes.

Aim for about 30 minutes of moderate exercise each day, such as walking outside, cycling, yoga, pilates, or swimming. Be sure to fuel your body appropriately before and after exercise and to give yourself rest days to properly recover.

6. Limit Exposure to Harmful Chemicals

Avoid eating and drinking out of plastic bottles and containers, which contain hormone-disrupting chemicals, and opt for filtered water and organic foods to help reduce your toxin load.

7. Get Mental and Emotional Support

While some factors that contribute to fatigue, chronic stress, and allostatic load are within your control, others are not, such as prenatal stress and early childhood stress.

This is why I recommend all patients work with a licensed mental health professional to develop tools to process, reduce, and recover from the stress that is bringing them down.

Key Takeaways on Causes of Fatigue and How to Increase Your Energy

In conclusion, fatigue can stem from various factors, including lifestyle habits, medical conditions, and nutritional deficiencies. It's crucial to address these underlying causes to combat fatigue and regain energy levels effectively. By adopting healthy lifestyle practices, seeking medical evaluation when necessary, and ensuring a balanced diet rich in essential nutrients like vitamin B12, iron, and protein, you're on your way toward overcoming fatigue and improving your overall well-being.

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About The Author

Dr. Jolene Brighten

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Dr. Jolene Brighten, NMD, is a women’s hormone expert and prominent leader in women’s medicine. As a licensed naturopathic physician who is board certified in naturopathic endocrinology, she takes an integrative approach in her clinical practice. A fierce patient advocate and completely dedicated to uncovering the root cause of hormonal imbalances, Dr. Brighten empowers women worldwide to take control of their health and their hormones. She is the best selling author of Beyond the Pill and Healing Your Body Naturally After Childbirth. Dr. Brighten is an international speaker, clinical educator, medical advisor within the tech community, and considered a leading authority on women’s health. She is a member of the MindBodyGreen Collective and a faculty member for the American Academy of Anti Aging Medicine. Her work has been featured in the New York Post, Forbes, Cosmopolitan, Huffington Post, Bustle, The Guardian, Sports Illustrated, Elle, and ABC News. Read more about me here.