Common causes of fatigue, and what to look at first

Fatigue most often traces back to one or more everyday causes, such as poor sleep, too little or too much activity, eating poorly, alcohol, stress or a medicine. Sometimes it is a symptom of an illness, such as anemia, a thyroid problem, sleep apnea, depression or diabetes. Your doctor can help sort out which.¹²

What are the most common causes of fatigue?

The most common causes are lifestyle factors: not enough sleep, too little or too much physical activity, eating poorly, and alcohol or drug use. Stress, low mood, certain medicines, hormonal changes and infections are also common. When tiredness has no clear reason and lasts, a medical condition may be behind it.¹²

The NHS lists these common causes of tiredness and fatigue:²

• Not getting enough sleep, or finding it hard to get to sleep.²
• Lifestyle habits such as a poor diet and little exercise.²
• Stress, depression and life challenges such as bereavement or looking after a new baby.²
• Hormonal changes, such as during puberty, pregnancy or menopause.²
• Some illnesses, like glandular fever and COVID-19, and some medicines, including chemotherapy.²

Medicines deserve a second look. Mayo Clinic lists allergy and cough medicines, and Cleveland Clinic lists sedatives and antihistamines.¹³ If you think a medicine is making you tired, talk with the doctor who prescribed it. Do not stop or change it on your own.

Some conditions come with a pattern. The NHS describes these examples, and says not to guess from a list:²

• Sleep apnea: tired by day, waking at night, gasping, snorting or choking sounds, and loud snoring.²⁸
• Iron deficiency anemia: low energy, noticeable heartbeats, shortness of breath and pale skin.²
• Diabetes: tiredness with strong thirst, passing urine more often, and weight loss.²⁶
• Overactive thyroid: tired all the time, trouble staying still, nervousness and muscle weakness.²
• Underactive thyroid: fatigue with weight gain, trouble tolerating cold, dry skin and heavy or irregular periods. The NIH notes that fatigue and weight gain are common and do not necessarily mean a thyroid problem.⁵
• ME/CFS (chronic fatigue syndrome): extreme fatigue for at least three months, with problems with thinking and memory.²⁷

When is tiredness a reason to see your doctor first?

See your doctor if resting, easing stress, eating well and drinking fluids for two or more weeks has not helped, if tiredness affects daily life, or if it comes with other symptoms such as weight loss or mood changes. Call 911 for fatigue with chest pain, shortness of breath, a fast or irregular heartbeat or fainting.¹²

Talk to your doctor first if you notice any of these along with tiredness:

• Weight loss you cannot explain. Cleveland Clinic advises seeing a provider whenever you lose weight without trying.¹⁰
• Fever, or night sweats that soak your clothes and bedding, especially with weight loss.⁹
• Getting out of breath more easily than usual, or noticeable heartbeats with pale skin. Sudden or severe shortness of breath is an emergency: call 911.²
• Very heavy periods. The NHS lists needing to change a pad or tampon every one to two hours, periods lasting more than seven days, and feeling tired or short of breath a lot.⁴
• Loud snoring, or gasping or choking at night, especially if someone has seen it.²⁸
• Strong thirst and passing urine more often than usual.²⁶
• Low mood that does not pass and affects sleeping, eating or working.²¹²
• Tiredness that began after you started a new medicine.¹
• Symptoms that last more than a few weeks with no clear reason.¹²

Emergency, call 911: fatigue with chest pain, shortness of breath, an irregular or fast heartbeat, a feeling you might pass out, severe stomach, pelvic or back pain, unusual bleeding, or a severe headache.¹

Crisis, call or text 988: if low mood comes with thoughts of harming yourself or suicide, call or text 988, the 988 Suicide & Crisis Lifeline, free and open all day and night. If life is in danger, call 911.¹¹¹¹²

Your doctor may order blood tests to check for conditions such as anemia, diabetes or an overactive thyroid.² Talk with your doctor about a diagnosis before you try to explain tiredness on your own. The habits below are education, and they work best alongside that care.

How do sleep, food timing and stress change energy?

Poor sleep, rushed or skipped meals and long-running stress can each lower energy, and they often feed each other. The CDC says adults aged 18 to 60 need seven or more hours of sleep, and that quality matters too. Feeling tired after enough sleep is one sign of poor sleep quality.¹³

Sleep. The CDC lists signs of poor sleep quality: trouble falling asleep, waking repeatedly in the night, and feeling sleepy or tired even after enough hours.¹³ If you often feel this way, talk with your doctor. A sleep disorder can be checked with tests such as a sleep study.¹³

Think of energy as something that grows from the soil of ordinary habits, such as when you sleep, when you eat and how you rest. If the soil is thin, it helps to look there first.

Food timing and caffeine. Mayo Clinic lists eating poorly as one lifestyle factor linked to fatigue.¹ A regular eating pattern you can keep is a reasonable starting point. Caffeine is worth a look. The FDA cites 400 milligrams a day, about two to three 12-ounce cups of coffee, as an amount not generally associated with negative effects in most adults. Too much can disrupt sleep.¹⁵ The CDC suggests avoiding caffeine in the afternoon and evening, and avoiding large meals and alcohol before bed.¹³

Stress. Stress is a common cause of fatigue.¹² The CDC says physical activity helps you feel better, function better and sleep better. It can also reduce short-term feelings of anxiety.¹⁴ But if activity leaves you much worse afterward, tell your doctor. That pattern, called post-exertional malaise, is a feature of ME/CFS.⁷

What about adrenal fatigue?

You may see "adrenal fatigue" offered as the reason for tiredness. The Endocrine Society says no scientific proof supports it as a true medical condition, and that there is no test that can detect it.¹⁶ A 2016 systematic review of 58 studies concluded that there is no evidence it exists as a condition.¹⁷ The concern is that the real cause may be missed. The tiredness is real. Depression, sleep apnea and adrenal insufficiency, a different and recognized condition, are among the things a doctor can check.¹⁶

What questions does a naturopathic consultation ask about energy?

A naturopathic consultation asks about your whole day: sleep, meals, movement, stress, medicines, and when your energy rises and dips. The aim is to find patterns worth sharing with your doctor. In a recorded interview, Dr. Werness said of a first visit, "I really want to know what's going on."

Questions often include:

• When did the tiredness start, and was there a change in your life around then?
• What time do you go to bed and get up, and do you feel rested?
• What do you eat and drink, including caffeine and alcohol?
• What medicines and supplements do you take? (Your doctor decides about any change.)
• What does stress look like for you right now?

Cleveland Clinic says a healthcare provider asks similar questions, then does a physical exam and sometimes lab tests.³ A naturopathic consultation does not replace those steps.

Which lifestyle habits are worth tracking for two weeks?

Track sleep, meals, caffeine and alcohol, movement, stress and energy for two weeks. A simple note each evening is enough. A sleep diary helps a provider understand what is going on, and two weeks is also when Mayo Clinic says to book a visit if rest and good habits have not helped.¹¹³

A one-line daily log can hold:

• Bedtime, wake time, and whether you woke in the night.¹³
• Meals, caffeine and alcohol, with times.¹³¹⁵
• Movement: any walk, stretch or workout, and how you felt afterward.¹⁴
• Energy at morning, midday and evening, on a scale of 1 to 5.
• Stress, mood, and any symptoms from the red flag list above.¹

Change one thing at a time. Bring the log to your doctor if tiredness continues.

How do you work alongside your doctor on this?

Start with your doctor for tests and answers about causes. Share your log, your medicines and your questions. Make habit changes alongside that care, not instead of it. If you take a prescribed medicine, talk with the doctor who prescribed it before you change anything.²³

Dr. Werness, ND, a naturopathic doctor, can help you turn habits like these into a plan you can keep, and you can share what you learn with your doctor.

Frequently asked questions

Fatigue often has more than one cause, and sleep, stress, mood, medicines and health conditions often overlap. The NHS advises against guessing the cause from a list; a doctor can work through the possible causes with you.² The questions below cover what people ask most.

Why am I always tired?

There is often more than one answer. Poor sleep, stress, low activity, diet, alcohol and medicines are common, and so are medical conditions.¹² If it has lasted a few weeks, see your doctor.²

Is low energy ever normal?

Yes. The NHS says it is normal to feel tired sometimes. It becomes a concern when you are tired all the time and do not know why.²

Could my tiredness be a medicine side effect?

It can be. Several medicines are linked to fatigue.¹³ Talk with the doctor who prescribed it. Do not stop it yourself.

Can supplements help with low energy?

That depends on the cause, and your doctor can check. Mayo Clinic lists low vitamin D among the causes linked to fatigue, so a test is the way to find out.¹ The Endocrine Society says tests offered for "adrenal fatigue" are not based on good scientific studies, and the reported remedy is not approved by the FDA.¹⁶

How a consultation with Dr. Werness approaches this

A consultation with Dr. Werness is about education and habits. You talk through your sleep, food, movement and stress, choose a few small steps, and keep your own doctor involved. He works alongside your doctor, not in place of your doctor. No result is promised.

To start, Take the Garden Check-in. When you are ready to talk it through, read about a naturopathic consultation with Dr. Maurice Werness, ND, a naturopathic doctor near Durham, North Carolina.

This page is for education. It does not replace advice from your own doctor.