Overview

Fatigue is a feeling of weariness, low energy, or lack of motivation. It can follow a busy day, poor sleep, stress, illness, or physical activity. It can also be a symptom of a medical, mental health, medication-related, or sleep-related problem.

This article explains common reasons fatigue can happen and when tiredness may need medical attention. It is not a way to diagnose the cause of fatigue.

Common causes

Lack of sleep is a common reason for fatigue. Short sleep, irregular sleep schedules, waking often, shift work, and poor sleep quality can all leave a person feeling worn down.

Stress can drain energy. Emotional strain, caregiving, work pressure, grief, or ongoing worry can affect sleep, appetite, concentration, and energy.

Physical activity can cause normal short-term tiredness, especially after unusually hard exercise or overexertion. Too little activity can also contribute to low energy over time.

Medicines may cause tiredness or drowsiness. Examples can include some allergy medicines, blood pressure medicines, sleep medicines, pain medicines, and medicines for nausea or mood conditions. Do not stop or change a prescribed medicine without medical advice.

Depression or anxiety can cause fatigue or make fatigue worse. Low mood, loss of interest, panic symptoms, worry, appetite changes, and sleep changes are worth discussing with a healthcare professional.

Anemia, thyroid issues, infections, chronic pain, and sleep disorders such as insomnia or sleep apnea are other possible causes. Fatigue can also occur with many long-term health conditions, after surgery, during recovery from illness, or with alcohol or drug use.

When to seek medical help

Contact a healthcare professional if fatigue lasts for weeks, is not explained by recent activity or sleep loss, interferes with daily life, or does not improve with adequate rest, nutrition, and lower stress. It is also reasonable to seek care if fatigue comes with fever, unintentional weight loss, night sweats, repeated headaches, feeling cold all the time, constipation, dry skin, or new weakness.

If fatigue may be related to a medicine, ask a clinician or pharmacist before making changes. The safest next step depends on the medicine and why it was prescribed.

Emergency warning signs

Contact a clinician right away or seek urgent care if fatigue occurs with confusion, dizziness, blurred vision, little or no urine output, or recent swelling with weight gain.

Thoughts of self-harm or suicide need immediate support. In the United States, call or text 988 for the Suicide and Crisis Lifeline, or call emergency services if there is immediate danger. Outside the United States, use local emergency or crisis resources.

What a clinician may check

A clinician may ask about sleep, work schedule, activity, diet, stress, mood, alcohol or drug use, medicines, recent illness, pain, and how long fatigue has been present. They may perform a physical exam, including checks of the heart, lymph nodes, thyroid, abdomen, and nervous system.

Depending on symptoms and medical history, tests may include blood counts, thyroid tests, kidney and liver function tests, blood sugar testing, inflammatory or infection-related tests, urinalysis, or sleep evaluation.

Self-care boundaries

General steps such as keeping a consistent sleep schedule, drinking enough fluids, eating regular meals, reducing alcohol, avoiding nicotine, managing stress, and gradually returning to activity may help some people. Keeping a fatigue diary can make patterns easier to discuss at a visit.

Self-care is not a substitute for evaluation when fatigue is persistent, unexplained, severe, or paired with warning signs. Caffeine and other stimulants are not reliable treatments for fatigue and can worsen sleep or lead to a crash when they wear off.

FAQ

Is fatigue the same as drowsiness?

No. Drowsiness is the need or urge to sleep. Fatigue is low energy or lack of motivation. A person can have one or both, and the difference can help a clinician narrow possible causes.

Will a clinician order labs for fatigue?

Sometimes. Labs are not needed for every tired day, but persistent or unexplained fatigue may lead a clinician to check for anemia, thyroid problems, infection, kidney or liver issues, diabetes, or other concerns based on the history and exam.

Can caffeine fix fatigue?

Caffeine may temporarily increase alertness for some people, but it does not address the underlying cause of fatigue. Too much caffeine or caffeine late in the day can interfere with sleep and make fatigue worse.

Sources

The sources listed for this article include MedlinePlus pages on fatigue and the MedlinePlus Medical Encyclopedia fatigue article.

Medical disclaimer

This content is for educational information only and does not replace professional medical diagnosis, treatment, emergency care, or advice from a qualified clinician.