Why am I so tired? 8 reasons you might be tired

Are you tired all the time? Learn about common causes of fatigue and ways to restore your energy.
Published November 19, 2020

If you've been dragging through your days lately, you might be tempted to reach for yet another cup of coffee and dismiss your fatigue as a normal consequence of being an adult in a hectic world. But constantly feeling drained can sometimes hint at an issue that goes beyond being busy or overscheduled. In a five-year study published in 2017, the majority of adult subjects experienced excessive daytime sleepiness at some point, with correlations pointing to a range of contributing factors, from mental health issues to metabolic disorders.

Feeling tired all the time isn’t a given. In many cases, pinpointing underlying causes of fatigue can help people reclaim their energy—and markedly improve their wellbeing, says Dr. Savita Ginde, MD, chief healthcare officer at Stride Community Health Center in Wheat Ridge, Colorado. Read on for some of the most common causes of tiredness, along with expert advice on how to manage them.

1. A stimulating sleep environment

Even if you head to bed at a decent hour each night fully intending to get the recommended seven to nine hours of shut-eye, certain factors in your midst can undermine sleep quality and leave you feeling less than rejuvenated in the morning. A few sleep stealers to watch out for include:

  • An overheated room. For most people, the ideal sleep temperature is a fairly cool 60°F to 67°F, according to the National Sleep Foundation. If you tend to keep your space toastier than that during the day, turning down the thermostat at night—and layering your bed with a blanket you can pull up or peel off as needed—might help you snooze more soundly.
  • Too much or too little noise. A cacophonous bedroom is an obvious detriment to sleep, but total silence might not be ideal, either. Research suggests that low levels of white noise—such as the steady whir of a fan—can help some people fall asleep more quickly and help mask outside noise disruptions (such as a barking dog) that would otherwise cause overnight waking. If noisy surroundings tend to keep you up, ear plugs might help, as well.
  • A phone right by your bed. Don’t let your Instagram habit sap your slumber. The screens of smartphones, tablets, and other electronic devices emit blue light, which can undermine ZZZs by suppressing levels of the sleep-promoting hormone melatonin. Consider adopting a screen-free stretch at night and giving your gadgets a separate bedtime—at least two hours prior to yours, suggests a 2017 study in the Journal of Psychiatric Research.
  • Clutter. Your bedroom should feel like a sanctuary, not a clutter catchall that stresses you out, Dr. Ginde says. Whatever “neat and restful” means to you, try to keep your sleeping environment in that zone. That might mean clearing piles of laundry off the bed or stashing work files in another room. In one survey by the National Sleep Foundation, respondents who reported making their bed every day were 19 percent more likely to say they slept well at night than those who left their sheets askew.

2. Caffeine and alcohol consumption

Those double-shot cappuccinos you sip to stave off the late-afternoon slump? They may wake you up in the moment, but the caffeine in such drinks can contribute to a larger cycle of tiredness, says Valerie Agyeman, a registered dietitian nutritionist and founder of Flourish Heights in Washington, D.C. Caffeine’s energizing effects can linger for a solid six hours after consumption, messing with sleep and leading to (you see where this is going) more fatigue the following day.

Caffeine’s impact can stretch even longer in the presence of certain medications, including birth control pills, MAOI-class antidepressants, and antibiotics such as ofloxacin and ciprofloxacin, Agyeman adds. If you suspect you are having sleep troubles due to the mingling of meds and mochaccinos, switch to decaf or chat with your healthcare provider about a more workable approach.

Another beverage category that can mess with sleep? Alcohol, says Dr. Mladen Golubic, MD, PhD, medical director for the Center of Lifestyle Medicine at Cleveland Clinic’s Wellness Institute. That may sound counterintuitive considering how drowsy most of us feel after a boozy drink or two. The issue, according to studies published in Alcoholism: Clinical & Experimental Research and elsewhere, is that alcohol can make it harder to fall asleep at your actual bedtime and may increase the likelihood of sleep disruptions later in the night. As a general practice, aim to have your final nightcap no fewer than four hours before bedtime, suggests a 2019 study of 700 adults in the journal Sleep.

3. Other dietary factors

Certain aspects of our diet may affect energy levels, too, Agyeman says. Here are some to consider as you plan your meals.

  • Simple carbs. OK, first things first: Whether in white bread or chocolate chip cookies, simple carbohydrates have gotten a not-quite-accurate reputation for causing blood sugar “spikes” and “crashes” that drain energy. WW’s science team is quick to clarify that the impact in healthy people isn’t that dramatic. Still, there is a kernel of truth: Unlike the simple sugars in refined and processed foods, complex carbs found in whole grains, fruits, veggies, legumes, nuts, and seeds tend to provide a more gradual, sustained energy release that can help keep tiredness at bay. Most health experts say that such nutritious sources of carbs can help form the foundation of a healthy diet.
  • High-fat diet. More reason to put plants on your plate: A large study of men published in the journal Nutrients found an association between a high-fat diet and a trio of sleep-related issues: tiredness during the day, sleep disruptions at night, and sleep apnea (a condition we’ll talk more about in a minute). The study wasn’t designed to ID the mechanisms at play, but the researchers note that high fat intake may affect orexin, a neuropeptide that plays a role in both arousal and appetite.
  • Dehydration. Keeping a water bottle handy may help keep your energy up. “When you’re dehydrated, the fluid loss causes a drop in blood volume, making the heart work harder to push oxygen and nutrients through the bloodstream to the brain and muscles,” Agyeman says. (You might feel tired just reading that.) Your personal water needs on any given day depend on factors such as activity level, the rest of your diet, even the weather. A simple calculation can help you figure out a good ballpark target.
  • Food allergies and intolerances. If you notice yourself feeling spent after consuming specific types of foods—say, dairy or beans—an allergy might be something to investigate. In certain people, food sensitivities and intolerances can set off fatigue through an inflammatory response, says Kristin Kirkpatrick, MS, RDN, manager of wellness nutrition services for Cleveland Clinic Wellness Institute. Before eliminating foods from your diet, see a doctor about testing, which may involve a skin prick, blood draw, or genetic screening.

4. Vitamin deficiency

You might experience persistent fatigue if you’re missing out on one or more key nutrients, Agyeman says. For adults in the U.S., shortfalls in the following are common.

  • Vitamin D. Only a small number of foods naturally contain vitamin D, and with age, skin loses some ability to synthesize the vitamin through sun exposure. This likely explains why more than 40% of Americans in a 2018 study were D-deficient. Tiredness is a common complaint: In a smaller, earlier study, 77% of patients who went to the doctor for fatigue had low blood levels of vitamin D—a strong correlation. If you want to bring more vitamin D into your diet, boost your intake of fatty fish, egg yolks, and fortified products such as milk. Catching a few minutes of solar rays on exposed skin can help, too. Otherwise, ask your doctor if you might benefit from taking a vitamin D supplement.
  • Vitamin B12. In addition to fatigue, symptoms of vitamin B12 deficiency may include weakness, loss of appetite, and tingling or numbness in the body’s extremities. Because this nutrient—needed to keep nerve cells healthy—occurs mostly in animal-derived foods such as meat, poultry, dairy products, and eggs, people who follow strict plant-based diets may find themselves falling short, says Dr. Yufang Lin, MD, an integrative medicine physician at Cleveland Clinic. Regardless of your diet, speak with your doctor if you are experiencing signs of B12 deficiency to ensure you’re getting an appropriate amount.
  • Iron. Humans need iron to make hemoglobin, the protein in red blood cells that carries oxygen throughout the body. If you’re low on iron—a condition known as anemia—you probably feel pretty worn out. “By not having enough red blood cells that can carry oxygen to tissues, you don’t make oxygen into adenosine triphosphate, which the body uses to produce energy,” explains Dr. Romy Block, MD, a specialist in endocrine and metabolic medicine and co-author of The Vitamin Solution: Two Doctors Clear the Confusion About Vitamins and Your Health. Other symptoms of iron-deficiency anemia include shortness of breath, brittle nails, and cracked skin at the sides of the mouth. A doctor can confirm with a blood test. Medical advice may include a recommendation to eat more iron-rich foods such as meat and leafy greens and/or take an iron supplement at a dose that’s right for you.

5. Chronic stress

In small bursts, stress can be beneficial, spurring the release of the hormone cortisol to help us focus and get things done, Dr. Golubic says. But when the body’s stress response doesn’t let up, it can cascade into fatigue and other effects.

Dr. Lin elaborates: “When the body stays in a constant elevation of cortisol, you’re perpetually experiencing a ‘fight or flight’ response. This is associated with elevated sugar, blood pressure, heart rate, inflammation, and a hypervigilant state. This high-alert state requires a lot of mental focus and physical energy, which contributes to both mental and physical fatigue.”

Stress can also exacerbate daytime tiredness by interfering with sleep onset, notes Dr. Lin.

Staying mentally healthy through stressful times is possible. There’s no surefire formula that works for everyone, but some stress-relieving methods known to be effective include physical activities such as yoga, as well as reframing anxious thoughts and meditation—the latter being a fave with Dr. Golubic. “Give it a try, five minutes a day, three times a week, building up to 20 minutes a day,” he suggests. “You may find yourself far more resilient and able to bounce back from stressful events more quickly.”

If you think you’d benefit from additional support in coping with chronic stress, connecting with a therapist might be helpful. The American Psychological Association offers this guide to getting started.

6. Medical conditions

Many common medical conditions can make people feel tired—sometimes as a result of disrupting sleep directly, sometimes by depleting energy in other ways. See your doctor if you are experiencing symptoms of the following. Generally, fatigue improves with treatment and management of these conditions.


Type 2 diabetes affects how the body handles blood sugar and responds to insulin. Insulin is a pancreatic hormone that helps move sugar out of the bloodstream and into cells for energy. With type 2 diabetes, the body either doesn’t produce enough insulin or becomes resistant to it, explains Dr. Jacqueline Jonklaas, MD, PhD, a professor of medicine in Georgetown University’s endocrinology division. If too much sugar remains in the bloodstream, the body’s energy needs can’t be met. Fatigue is a common symptom of type 2 diabetes, along with frequent urination, unusual thirst, and vision changes. Type 2 diabetes can develop over years and often starts with prediabetes.

Doctors can diagnose prediabetes and diabetes with blood screenings, Dr. Jonklaas explains. Lifestyle changes—such as stepping up your activity level and eating a nutritious diet focused on whole foods—can go a long way toward managing these conditions. Medications may be helpful, as well. With treatment, Dr. Jonklaas notes, “energy levels would be expected to improve.”

Thyroid disorders

The thyroid, a butterfly-shape gland in the front of the neck, makes hormones that regulate the body’s production of energy—a role more succinctly known as metabolism. In cases where the thyroid overproduces hormones (a condition called hyperthyroidism), a person may feel anxious and too keyed up to sleep well. On the flip side, if the thyroid underproduces hormones (hypothyroidism), a person may find themselves tiring out with simple tasks. In either case, exhaustion is common. Thyroid disorders are generally treatable with oral medication, Dr. Golubic says.

Autoimmune disorders

An autoimmune disease occurs when the body’s defence system mistakes normal cells for foreign cells and attacks them. Thought to affect at least 5% of the U.S. population, autoimmune diseases can develop in almost any area of the body and include rheumatoid arthritis, multiple sclerosis, lupus, fibromyalgia, endometriosis, and dozens more. Symptoms vary widely depending on the disorder, but one common thread is persistent fatigue due to underlying inflammation, Dr. Golubic says. Other symptoms shared across many autoimmune disorders: joint or muscle pain, swollen glands, and nagging low fevers.

Due to lack of testing methods, some autoimmune disorders are more challenging for doctors to diagnose than others. If you are experiencing symptoms, see a healthcare provider who can take a complete medical history and consider your total health picture.

Heart disease

Some people living with heart disease, coronary artery disease, or arrhythmias experience tiredness or weakness due to reduced flow of oxygenated blood to the body’s tissues, Dr. Block says, noting that fatigue generally improves when the underlying heart issue is addressed. In some cases, lifestyle adjustments such as switching to a Mediterranean-style diet or getting consistent physical activity can be effective at reversing or stopping the progression of heart disease. Some people may be advised to take medication or undergo a surgical procedure.

Sleep apnea

Daytime exhaustion is a common sign of sleep apnea, a disorder marked by brief episodes of breathing cessation during sleep. “When you repeatedly stop breathing for short intervals throughout the night, it’s harder to achieve REM—the deepest phase of sleep—which is why many feel fatigued the next day,” Dr. Ginde says. Other signs of sleep apnea include gasping for air upon waking, waking with a dry mouth, and morning headache. Men are more likely than women to develop sleep apnea, as are people who smoke. Advancing age, family history, and use of alcohol or sedatives can raise the risk, as well.

Diagnosis generally involves a noninvasive sleep test to monitor breathing overnight, says Dr. Ginde. Treatment may involve continuous positive airway pressure (CPAP) therapy or a mouthguard for sleeping.


An estimated 75% of people living with depression also experience insomnia, research has found, and inadequate sleep can play into low energy the following day. Many studies suggest that insomnia and depression have a bidirectional relationship, meaning that each influences the other: Insomnia may exacerbate depressive episodes, and depression may raise the risk of insomnia.

The good news is that depression is a treatable disorder. If you are experiencing daytime fatigue or nighttime sleep trouble along with sadness, hopelessness, apathy, body aches, or difficulty concentrating or making decisions, seeing a mental healthcare provider may help, Dr. Lin says. Ask your physician for a referral, or search for a therapist near you via an online national directory.

Chronic fatigue syndrome

This condition reflects tiredness right in its name: Chronic fatigue syndrome (CFS) is defined as six or more months of extreme fatigue and sleep trouble, and can also include loss of memory, mood changes, and joint pain. Managing the syndrome often involves interventions for individual symptoms. “Presently, the standard treatment for CFS focuses on supporting sleep quality, reducing pain, and supporting mood,” Dr. Lin says.

7. Sedentary lifestyle

You might expect workouts to wear you out, not fire you up. In fact, says Dr. Lin, regular exercise can have a vitalizing effect. “When we are moving our body through routine exercise, we strengthen our muscles, increase lung capacity, improve circulation, increase insulin sensitivity, improve our mood, and overall feel more energetic,” she says.

Sure enough, a small, six-week study published in Psychotherapy and Psychosomatics showed that among adults who were sedentary and experiencing persistent fatigue, adopting a routine of low-intensity activity (such as walking) was tied to a 65% reduction in fatigue scores. A 2014 study of 73 women uncovered a similar correlation between physical activity and self-reported energy levels.

It’s never too late to start living a more active lifestyle, Dr. Lin assures. Even small steps toward making physical activity a habit can make a difference in your wellbeing.

8. Medications

Many widely used medicines—both prescription and over-the-counter forms—list fatigue as a potential side effect. The partial list below was compiled by the National Sleep Foundation.

  • Antihistamines such as diphenhydramine, found in some OTC sleeping pills and allergy meds
  • Alpha blockers, used to treat conditions such as high blood pressure
  • Beta blockers, for high blood pressure or anxiety
  • Antidepressants
  • Antiemetics, used to control nausea and vomiting
  • Antipsychotics and anticonvulsants
  • Benzodiazepines and sedative-hypnotics, commonly prescribed for anxiety or insomnia
  • Medications for Parkinson’s disease
  • Muscle relaxants
  • If you take any of the above and find yourself struggling with daytime sleepiness or lethargy, it may help to speak with your doctor about adjusting your dose or switching to another medicine.

The upshot: Why are you always feeling tired?

Fatigue is such a common experience, many of us may brush it off as a superficial side effect of a busy life. Understandable. But experts say it’s important to know that tiredness can sometimes be a sign of health issues that warrant medical attention. “There can be many reasons a person experiences sleepiness and fatigue during the day,” reiterates Dr. Ginde. “If it persists for more than two weeks, it’s advisable to visit your doctor to find out why.”

Tiredness doesn’t have to be a chronic complaint. Working with a healthcare provider can point you toward understanding the cause of your fatigue—and a personalized plan that supports your health and energy.


Maressa Brown is a writer and editor in Los Angeles specializing in health and lifestyle topics. She’s written for Shape, InStyle, Parents, The Washington Post, Cosmopolitan, Better Homes and Gardens, and Women’s Health, among other outlets.