Life requires energy to fuel your cells and keep your body functioning, says Samuel Werner, DO, founder of Family Osteopathy in West Hartford, Connecticut. Ideally, your body operates with an energy surplus, but if you have depleted energy stores due to stress, hormonal issues, or lack of sleep, you may feel tired, Dr. Werner explains. “Fatigue is a sign that you’re operating at an energy deficit,” he adds.
While it’s normal to feel tired from time to time, chronic fatigue can have a number of causes, says Dr. Werner.
Most adults need seven to nine hours of sleep each night to function optimally, says Brooke Judd, MD, chief of the section of sleep medicine at Dartmouth Hitchcock Medical Center in Lebanon, New Hampshire. However, one-third of adults routinely get less than seven hours of sleep per night, according to the Centers for Disease Control and Prevention (CDC).
Not getting enough sleep can cause symptoms such as fatigue, excessive daytime sleepiness, irritability and difficulty concentrating, says Dr. Judd. What’s more, chronic sleep deprivation is associated with an increased risk of mental illness, heart disease, high blood pressure, obesity, immune system damage, and increased sensitivity to pain.
Many medical conditions can disrupt sleep and cause fatigue, says Po-Chang Hsu, MD, medical content expert at SleepingOcean.com. These conditions may include:
Obstructive sleep apnea, a sleep disorder characterized by sudden pauses in breathing that cause frequent awakenings during the night, Dr. Hsu says. This condition often leads to fragmented, non-restorative sleep, according to research.
Hypothyroidism, or reduced thyroid hormone production, is associated with shorter sleep duration, sleep compensation (the time it takes to wake up), and reduced overall sleep quality, Dr. Hsu says. In general, fatigue is a common symptom of hypothyroidism.
Cancer and cancer treatment can cause chronic fatigue due to surgery, infection, changes in hormone levels, low blood counts, or low electrolyte levels. Also, during chemotherapy or radiation, healthy cells are damaged along with cancerous ones, and as the body uses energy to repair damaged cells, chronic exhaustion can occur, Dr. Hsu says.
Chronic fatigue syndrome is characterized by insurmountable fatigue. Although the cause of the condition is unknown, common causes include severe psychological stress and viral infections, Dr. Hsu says.
Multiple sclerosis (MS) is a disease that can cause severe fatigue. In fact, fatigue affects 75 percent of MS patients, according to a journal article a dream. Potential causes of MS-related fatigue include damage to the brain and central nervous system, but this symptom is still poorly understood, according to research.
Chronic kidney disease causes fatigue in about 70% of patients. This is likely caused by a build-up of toxins in the blood and/or anemia, a condition in which the body does not produce enough red blood cells, resulting in a lack of oxygen delivered to the organs, a common complication of kidney disease.
Patients with type 1 or type 2 diabetes often experience fatigue due to a lack of insulin in the body. As a result, cells don’t get the glucose or energy they need to function normally, which can lead to exhaustion, Dr. Hsu explains.
fibromyalgia is characterized by severe and widespread body pain that can negatively affect a person’s quality of life and sleep, leading to low energy levels and fatigue, says Dr. Hsu. Additional side effects of fibromyalgia such as unrefreshing sleep, anxiety, depression, and cognitive difficulties can worsen fatigue.
Infection (bacterial, viral, or parasitic) can cause fatigue as the body’s immune system tries to repair itself, says Erica Steele, a naturopathic doctor at Holistic Family Practice in Virginia Beach, Virginia.
Menopause often causes sleep disturbances due to changes in hormone levels, hot flashes, night sweats and other factors.
Lack of physical activity
Physical activity levels can affect fatigue, says Maddie Pasquariello, a registered dietitian at Nutrition with Maddie in Brooklyn, New York. “Although vigorous physical activity can make us feel more tired (because we expend energy and need to restore it), regular physical activity several times a week can actually increase overall energy levels,” she says.
Frequent exercise causes our bodies to produce more mitochondria, the part of the cell responsible for producing energy, which increases the amount of energy our body can produce, Pasquariello says. However, a sedentary lifestyle leads to reduced mitochondrial function, lower energy levels and fatigue.
Certain nutritional deficiencies, particularly deficiencies in vitamin D, vitamin B12, and vitamin C, as well as sodium, zinc, magnesium, iron, and fatty acids, can lead to fatigue, Pasquariello says. Vitamin D, which is produced in our bodies after exposure to sunlight, is one of the most common vitamin deficiencies, she says.
Overindulging in unhealthy snacks and processed foods throughout the day, such as sugary drinks and baked goods, can also be problematic, Dr. Hsu says. These foods cause a sudden spike in blood sugar and can cause a feeling of a quick burst of energy followed by a sudden drop in energy levels, leading to daytime fatigue, he explains.
Daily and chronic stress are among the main causes of poor sleep and insomnia, says Dr. Hsu. Internalized stress can stem from holding back difficult emotions, lacking emotional coping mechanisms, or an inability to communicate feelings or thoughts, Dr. Steele adds.
What’s more, people who have experienced unresolved trauma tend to be hypervigilant, meaning their brains remain in a heightened state of alertness, making sleep difficult, Dr. Steele says.
Depression and anxiety
Many mental and behavioral conditions can contribute to chronic fatigue and/or sleep problems, says Aaron Sternlicht, an addiction specialist and co-founder of Family Addiction Specialist, based in New York. For example, depression or low mood can cause fatigue and insomnia, he adds.
“Anxiety is another common mental health problem whose symptoms include fatigue and sleep disturbances,” says Sternlicht. If persistent exhaustion or sleep problems aren’t related to a physical health problem, Sternlicht recommends seeking a mental health professional for an evaluation.
Caffeine intake affects the quality and quantity of our sleep, Pasquariello says, and drinking too much caffeine can cause insomnia. Caffeine has a half-life of about five to six hours, so if you drink a cup of coffee at 9 a.m., only half of it remains in your system by 3 p.m. (when many people start feeling sleepy or sluggish), Pasquariello explains.
“The more caffeine we drink during the day, the more [may start] eating away at the quality and quantity of sleep we get,” she says.
Water plays a vital role in our bodies: it’s responsible for distributing nutrients around our cells, removing waste, regulating temperature, and more, Pasquariello says. “When we’re dehydrated, these basic functions can’t happen and our bodies react to conserve energy, which makes us feel sleepy,” she says.
Dehydration can also make the blood thicker, making it harder for the heart to pump blood throughout the body, which can contribute to fatigue, Dr. Hsu adds.
Obese individuals may be at higher risk for daytime fatigue and sleepiness, regardless of whether they also experience sleep apnea and general sleep loss, Pasquariello says. This can be due to co-existing conditions, such as diabetes, depression and metabolic diseases, she says. These conditions are not unique to obese people, but obesity increases the risk for each of them.
Excessive alcohol use leads to poor sleep quality, says Sternlicht. “Although alcohol can help people sleep, it disrupts rapid eye movement (REM) sleep,” he says. REM sleep begins about 90 minutes after falling asleep and is the period of sleep in which most dreaming occurs. Your eyes dart back and forth and your limbs become temporarily paralyzed during this stage of sleep. Alcohol’s sedative effect wears off after a few hours, leading to fragmented sleep for the rest of the night, and chronic alcoholism is linked to serious sleep disturbances, according to a 2018 study. Handbook of Clinical Neurology.
Some medications can affect sleep quality or cause daytime sedation (tiredness), says Dr. Judd. Medications that can make it difficult to sleep include stimulants, antidepressants (especially bupropion or Wellbutrin), inhaled corticosteroids, oral corticosteroids (such as prednisone), decongestants containing pseudoephedrine or phenylephrine, and beta-blockers. If you have trouble sleeping or feel tired during the day, ask your healthcare provider if any of your medications may be contributing to your fatigue.
Seasonal and year-round allergies commonly cause fatigue due to symptoms such as congestion, sneezing, and general malaise, which can make it difficult to get quality sleep. The release of histamines caused by allergic triggers also causes fatigue.