Doctors Explain 15 Reasons for Low Energy and Chronic Fatigue

Everyone feels wiped here and there, but when it’s a constant issue, it’s understandable to wonder why you’re always tired. Unfortunately, you’re not the only person grappling with this.

Data from the Centers for Disease Control and Prevention (CDC) found that 13.5% of American adults say they feel tired or exhausted most days or every day of the week. Of course, sometimes there are obvious reasons for this, like you haven’t been able to consistently log the recommended seven-plus hours of sleep a night. But sometimes the reason for your fatigue can be puzzling.

Meet the Experts: Sandra Adamson Fryhofer, M.D., an internal medicine doctor in Atlanta; Jessica Cording, R.D., the author of The Little Book of Game-Changers; Laurence Corash, M.D., adjunct professor of laboratory medicine at the University of California, San Francisco; Keri Gans, R.D.N., a dietitian and host of The Keri Report podcast; Robert J. McConnell, M.D., co-director of the New York Thyroid Center at Columbia University Medical Center in New York City, et al.

In can be tough in some situations to pinpoint the exact cause of your fatigue. But, in many cases, the reason for your lack of energy could be due to lifestyle habits or an underlying health issue that’s treatable. Whatever is causing you to be so tired, it’s crucial to check in with a healthcare provider if this is an ongoing thing for you, says Sandra Adamson Fryhofer, M.D., an internal medicine doctor in Atlanta.

While you’re waiting to be seen, check out the list of possible reasons for fatigue below to help you try to narrow the field. These could help to explain your persistent sluggishness, according to doctors and dietitians.

Anemia

The fatigue caused by anemia is the result of a lack of red blood cells, which bring oxygen from your lungs to your tissues and cells. You may feel weak and short of breath. Anemia may be caused by an iron or vitamin deficiency, blood loss, internal bleeding, or a chronic disease such as rheumatoid arthritis, cancer, or kidney failure.

Women of childbearing age are especially susceptible to iron deficiency anemia because of blood loss during menstruation and the body’s need for extra iron during pregnancy and breastfeeding, explains Laurence Corash, M.D., adjunct professor of laboratory medicine at the University of California, San Francisco.

Symptoms include feeling tired or fatigued all the time, extreme weakness, difficulty sleeping, lack of concentration, rapid heartbeat, chest pains, and headache. Simple exercise, such as climbing the stairs or walking short distances, can wipe you out.

A thorough evaluation for anemia includes a physical exam and blood tests, including a complete blood count (CBC), to check the levels of your red blood cells and the hemoglobin in your blood. It’s also standard to check the stool for blood loss.

As far as treatments go, anemia isn’t a disease; it’s a symptom that something else is going on in your body that needs to be resolved. So, treatment will vary depending on the underlying cause of anemia. It may be as simple as eating more iron-rich foods but talk to your doctor about the right treatment for you.

Thyroid disease

When your thyroid hormones are out of whack, even everyday activities will have you down for the count. The thyroid gland, about the size of the knot on a suit tie, is found in the front of the neck and produces hormones that control your metabolism. Too much thyroid hormone (hyperthyroidism), and metabolism speeds up. Too little (hypothyroidism), and metabolism slows down.

Hyperthyroidism causes muscle fatigue and weakness, which you may notice first in the thighs. Exercises such as riding a bike or climbing stairs become more difficult. Other thyroid symptoms include unexplained weight loss, feeling warm all the time, increased heart rate, shorter and less frequent menstrual flows, and increased thirst. Hyperthyroidism is most commonly diagnosed in women in their 20s and 30s, but it can occur in older women and men too, says Robert J. McConnell, M.D., co-director of the New York Thyroid Center at Columbia University Medical Center in New York City.

Hypothyroidism causes fatigue, an inability to concentrate, and muscle soreness, even with minor activity. Other symptoms include weight gain due to water retention, feeling cold all the time (even in warmer weather), heavier and more frequent menstrual flows, and constipation. Hypothyroidism is most common in women over age 50; in fact, as many as 10% of women past 50 will have at least mild hypothyroidism, says Dr. McConnell.

Thyroid disease can be detected with a blood test. “Thyroid disorders are so treatable that all people who complain of fatigue and/or muscle weakness should have the test done,” says Dr. McConnell. Thyroid disease treatments vary, but may include medications, surgery, or radioactive iodine.

Type 2 diabetes

More than 23 million people in the United States have been diagnosed with type 2 diabetes, but an additional 7.2 million people may not even realize that they have it, according to research from the CDC. Sugar, also called glucose, is the fuel that keeps your body going. And that means trouble for people with type 2 diabetes who can’t use glucose properly, causing it to build up in the blood. Without enough energy to keep the body running smoothly, people with diabetes often notice fatigue as one of the first warning signs, according to the American Diabetes Association.

Aside from feeling tired all the time, other signs of type 2 diabetes include excessive thirst, frequent urination, hunger, weight loss, irritability, yeast infections, and blurred vision.

There are two major tests for type 2 diabetes. The A1C test, which is most common, shows your average blood sugar level over the course of a few months. The fasting plasma glucose test measures your blood glucose level after fasting for eight hours.

There is no cure for diabetes. Your doctor will advise you on how to control your symptoms through diet changes, oral medications, and/or insulin.

Depression

More than “the blues,” depression is a major illness that affects the way we sleep, eat, and feel about ourselves and others. Without treatment, the symptoms of depression may last for weeks, months, or even years.

We don’t all experience depression in the same way. But commonly, depression can cause decreased energy, changes in sleeping and eating patterns, problems with memory and concentration, and feelings of hopelessness, worthlessness, and negativity.

There’s no blood test for depression, but your doctor may be able to identify it by asking you a series of questions. If you experience five or more of these symptoms below for more than two weeks, or if they interfere with your life, see your doctor or mental health professional: fatigue or loss of energy; sleeping too little or too much; a persistent sad, anxious, or “empty” mood; reduced appetite and weight loss; increased appetite and weight gain; loss of interest or pleasure in activities once enjoyed; restlessness or irritability; persistent physical symptoms that don’t respond to treatment, such as headaches, chronic pain, or constipation and other digestive disorders; difficulty concentrating, remembering, or making decisions; feeling guilty, hopeless, or worthless; thoughts of death or suicide.

As far as treatments are concerned, most people who struggle with depression are able to manage it through a combination of talk therapy and medication.

Chronic fatigue

This baffling condition causes a strong fatigue that comes on quickly. People who suffer from chronic fatigue syndrome (CFS) feel too tired to carry on with their normal activities and are easily exhausted with little exertion.

Other signs include headache, muscle and joint pain, weakness, tender lymph nodes, and an inability to concentrate. Chronic fatigue syndrome remains puzzling because it has no known cause.

There are no tests for this. Your doctor must rule out other conditions with similar symptoms, such as lupus and multiple sclerosis, before making the diagnosis.

Unfortunately, there is no approved medicinal cure for chronic fatigue. Self-care, antidepressants, talk therapy, or joining a support group may help.

Sleep apnea

You could have this sleep-disrupting problem if you wake up feeling tired no matter how much rest you think you got. Sleep apnea symptoms include brief interruptions of breathing during sleep. In the most common type, obstructive sleep apnea, your upper airway actually closes or collapses for 10 seconds or more, which prevents your brain from going into deeper stages of sleep like the REM stage. Someone with obstructive sleep apnea may stop breathing dozens or even hundreds of times a night, says Roseanne S. Barker, M.D., former medical director of the Baptist Sleep Institute in Knoxville, Tennessee.

Sleep apnea is often signaled by snoring and is generally followed by tiredness the next day. Because sleep apnea can lead to heart disease, high blood pressure, and stroke, it’s important to be tested.

Your doctor may refer you to a sleep specialist who may want to perform a sleep study either at home or in a lab. This may involve an overnight stay at a sleep clinic, where you’ll undergo a polysomnogram, which is a painless test that will monitor your sleep patterns, breathing changes, and brain activity.

If you’re diagnosed with sleep apnea, you may be prescribed a CPAP (continuous positive airway pressure) device, a mask that fits over your nose and/or mouth and blows air into your airways while you sleep.

B12 deficiency or insufficiency

Getting enough vitamin B12 is crucial for brain health, your immune system, and your metabolism. As we age, though, our ability to absorb B12 declines. Low B12 commonly shows up as fatigue, according to Keri Gans, R.D.N., a dietitian and host of The Keri Report podcast. Certain diabetes and heartburn medications and digestive disorders like irritable bowel syndrome (IBS) and Crohn’s disease hinder your body’s ability to absorb B12. And if you follow a plant-based diet, you also have an increased risk, because B12 occurs naturally only in meat, eggs, shellfish, and dairy.

In addition to fatigue, you may be low on B12 if you’re experiencing bouts of tingling in hands and feet, memory lapses, dizziness, anxiety, and vision problems. If your doctor expects you’re low on B12, you’ll undergo a simple blood test. Depending on your blood test results, your doctor may suggest working more dietary sources of B12 into your eating plan or taking a vitamin B12 supplement.

Long COVID

This one can be tricky to pinpoint, but it’s important to consider if you’ve had COVID-19. Post-COVID conditions, a.k.a. long COVID or long-haul COVID, is an umbrella term used to describe a range of new, returning, or ongoing health problems people can have for weeks, months, or years after they were first infected with COVID-19, per the CDC. Even people who had minor symptoms of the virus or no symptoms at all can develop post-COVID conditions.

There are a lot of different potential symptoms you can experience if you have long COVID, but tiredness and fatigue are common, says Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York. “It can be incredibly disruptive,” he says. “Some people aren’t able to make it through the day without taking a nap.” That can be difficult to navigate if you need to be at work or school during that time, he points out.

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In addition to fatigue, you may have symptoms like trouble breathing or shortness of breath, feel more tired after doing physical or mental activities, or have mental fog, a lingering cough, joint or muscle pain, sleep problems, dizziness when you stand up, and changes in your ability to smell and taste things, per the CDC.

Unfortunately, there are no laboratory tests to diagnose long COVID.

While being fully vaccinated can help prevent it, there are no set treatments for long COVID, but your doctor may be able to offer up specific advice based on your situation. “It just tincture of time at this point for fatigue and long COVID,” Dr. Russo says. But, he adds, it’s important to see your doctor to rule out any non-COVID cause since long COVID is a “diagnosis of exclusion.”

Heart disease

Heart disease is an umbrella term for a range of conditions that can impact your heart, including coronary artery disease, arrhythmias, heart infections, and diseases of the heart muscle, according to the Mayo Clinic.

Heart disease is the leading cause of death for men and women in the U.S., per the CDC, making this a condition you don’t want to take lightly. There are a lot of potential symptoms of heart disease, but fatigue is one of them—particularly with cardiomyopathy (a disease of the heart muscle), heart valve problems, and endocarditis (an infection that affects the inner lining of your heart chambers and heart valves).

Symptoms depend largely on the type of heart disease you have, but can include chest pain, shortness of breath, swelling in your legs, ankles, and feet, and changes in your heart rhythm, along with fatigue.

If your doctor suspects you have heart disease, they’ll likely want to do a blood test and chest X-ray, along with diagnostic tests like an electrocardiogram to measure the electrical activity in your heart and a cardiac MRI to get detailed imaging of your heart, per the Mayo Clinic. Treatments can vary depending on the type of heart disease you have, but may include things like lifestyle changes (specifically focusing on a low-fat, low-sodium diet), certain medications, and even surgery.

Rheumatoid arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease that impacts the joints. Those with RA experience chronic joint pain, swelling, weakness, and, you guessed it, fatigue, according to the CDC. The condition may also affect the lungs, heart, and eyes.

According to the CDC, RA symptoms include pain or aching in more than one joint, stiffness in more than one joint, tenderness and swelling in more than one joint, weight loss, fever, weakness, and fatigue. People with RA also often experience the same symptoms on both sides of the body.

A combination of physical exams, blood work, and X-rays are required to diagnose RA. Because RA symptoms can resemble those of other inflammatory joint conditions, it’s important to receive a proper diagnosis from a rheumatologist. There are a variety of medications that can be prescribed to treat RA, per the CDC, and those are often combined with self-management strategies such as staying active and avoiding injury to prevent the disease from progressing.

Nutritional deficiencies

Various nutritional deficiencies (like Vitamin D, B12, and iron) can cause our cells distress, notes William B. Miller, Jr. M.D., infectious disease expert, evolutionary biologist, and author of Bioverse: How the Cellular World Contains the Secret to Life’s Biggest Questions. “The cells of our body experience this as stress, and that stress makes you tired.” As for how to combat this, Dr. Miller says to first “substantially increase your intake of plant-based fibers. Our hunter-gatherer ancestors had a very high diet of these types of nutrients. Our modern diet is sadly deficient in fiber. Your good microbes depend on these fibers as essential nutritional elements. Also, consider adding a probiotic. These are supplemental living bacteria that can be added to boost the number of beneficial microbes in your gut.”

Dr. Miller also says to cut sugars, processed foods, and excess salt while you’re at it.

Too much caffeine

While this might seem counterintuitive—caffeine is supposed to give you energy, after all—it’s true. “Extra caffeine is not contributing any beneficial health effect because your cells have become overwhelmed, and that excess caffeine no longer provides any boost,” explains Dr. Miller. He does note that the amount that constitutes too much is individualized. “Excess caffeine leads to a loss of energy,” he says.

Jessica Cording, R.D., the author of The Little Book of Game-Changers, says she sees this a lot. “In the short-term, you might feel like you’re getting more energy but then there tends to be a crash,” she says. “It’s like putting a flimsy Band-aid on a problem.”

While there is a difference between drinking too much caffeine and a caffeine overdose, the signs of overdoing it are similar to those of a panic attack. Some symptoms of caffeine overdose, per Mount Sinai, include breathing issues, dizziness, changes in alertness, agitation, seizures, diarrhea, irregular heartbeat, increased thirst, increased urination, and more.

What might be too much caffeine for you could be just right for someone else. Unfortunately, trial and error is the best method for figuring out your limit. But, be sure to reference Food and Drug Administration (FDA) guidelines if you’re unsure.

Dehydration

If you’re not making a point to drink enough water daily, it‘s very possible that your exhaustion is a symptom of dehydration. According to the Mayo Clinic, fatigue, along with dizziness and confusion, are tell-tale symptoms.

But you can even feel sluggish when you’re mildly dehydrated, according to Cording. “All of your cells have to work harder to do what they need to do when you’re mildly dehydrated,” she says.

Menopause

Menopause can cause some to experience trouble sleeping due to fluctuating hormone levels. A lack of restorative rest, and the general discomfort menopause can bring, can certainly manifest as relentless fatigue. Remedies vary from person to person, including hormone therapy, but making sure your sleep environment is comfortable and cool is key.

Inconsistent eating

You don’t need to force yourself to eat when you’re not hungry, but spacing your meals really far apart or eating at odd hours can throw your blood sugar out of whack, leading to fatigue, according to Gans. “A consistent eating pattern can go a long way toward preventing low energy,” she says.

Cording says this is a common issue with intermittent fasting. “Some people may get up and exercise at 5 a.m. but then try to hold off for several hours to have breakfast,” she says. “That will definitely contribute to fatigue.”

Diet can play a big role in how fatigued you feel, according to Cording. “One of the most common things I see contribute to fatigue is poorly-controlled blood sugar,” she says. “If someone’s blood sugar is up and down all day, or if it’s chronically too low or too high, it can make them feel tired.”

There are also certain underlying health conditions, like type 2 diabetes, that can be impacted by nutrition, Cording says. Proper nutrition is also crucial when it comes to refueling after workouts, she explains.

In your day-to-day, Gans suggests focusing on having regular meals with protein, high-fiber carbs such as 100% whole grains, fruits, vegetables, and healthy fats, while staying hydrated. “If you need energy in the moment, have a meal or snack that includes carbohydrates for readily available fuel and protein for longer-lasting energy,” she says.

If you’re having fatigue but aren’t sure if it warrants a trip to the doctor just yet, Kelly Waters, M.D., a sleep and neurology physician at Spectrum Health, recommends trying to make a few changes at home to see if they help. Those include:

• Take breaks during the day. This can help you refocus.
• Alternate boring tasks with more active ones. That can be as simple as getting up and walking to check your mail after paying your bills online.
• Try to be more physically active. Sometimes fatigue can be due to a lack of activity, Dr. Waters says. Making a point to get the recommended 150 minutes of physical exercise a week may help.
• Make sure you take time for things you enjoy. Stress and even boredom can lead to fatigue, Dr. Waters points out, so trying to get hobbies and other things you like into your day may help.
• Stay hydrated. Drinking plenty of water can help prevent dehydration-related fatigue.
• Limit caffeine. The cups-of-coffee sweet spot is different for everyone, but try limiting the daily dose to two to avoid a hard crash.
• Prioritize a consistent sleep schedule. Even on the weekends.
• Manage stress. Yoga, breath work, and therapy are all great tools for getting centered.

While making certain lifestyle tweaks could help with your fatigue, it’s unlikely to do much if you’re struggling with an underlying health condition. “If you feel like you are eating well-balanced meals, sleeping well, and staying active, and none of the obvious things seem to be at play, it’s a good time to check in with your doctor,” Cording says.

That’s especially true if the fatigue is constant and is impacting your daily activities, Dr. Water says.

You know what it means to be tired—you likely feel that way every night before bed. But fatigue is slightly different. When you’re fatigued, you have unrelenting exhaustion that lasts longer than normal tiredness, and it’s usually not helped by getting rest, the Mayo Clinic says.

“Symptoms of fatigue can include low energy, feeling unmotivated, or feeling unfocused,” says Dr. Waters. And that can lead to other symptoms like pain issues including headaches, restless legs, muscle aches, and insomnia. “It may translate to not completing tasks through your day, or not being able to focus on a project,” Dr. Waters says. “Fatigue does not have to be constant, it can fluctuate.”