Fatigue

Fatigue is a persistent feeling of tiredness, low energy or lack of physical or mental stamina. It can occur with respiratory infections and lung conditions, but may also result from poor sleep, anemia, stress, medications or other medical conditions.

Medically Reviewed
Dr. Nabila Zaheer Consultant Pulmonologist
Last Updated
Sep 04, 2026
Fatigue
2 min estimated read

Overview

Fatigue is more than ordinary tiredness after physical activity. A person with fatigue may feel exhausted, lack energy, have difficulty concentrating or find normal daily activities more difficult. Fatigue is common during and after infections. Respiratory conditions such as influenza, COVID-19, pneumonia, tuberculosis and chronic lung diseases can cause significant fatigue. Persistent or unexplained fatigue may require medical evaluation to identify the underlying cause.

Causes

Common causes of fatigue include: Viral infections such as influenza and COVID-19 Pneumonia and other respiratory infections Tuberculosis Chronic obstructive pulmonary disease (COPD) Asthma, particularly when symptoms are poorly controlled Sleep disorders, including sleep apnea Anemia or nutritional deficiencies Poor sleep or insufficient rest Stress, anxiety or prolonged emotional strain Certain medications Thyroid and other metabolic conditions Chronic medical conditions Dehydration Reduced physical fitness or prolonged inactivity

Risk Factors

Factors that may increase the likelihood of fatigue include: Chronic respiratory or other medical conditions Recent infection Poor sleep or irregular sleep schedules Sleep apnea or other sleep disorders Nutritional deficiencies Anemia Prolonged stress Dehydration Certain medications Smoking Physical inactivity Older age or multiple chronic health conditions

Diagnosis

A doctor will usually ask about the duration and severity of fatigue, sleep patterns, medications, lifestyle and other symptoms. Depending on the suspected cause, evaluation may include: Physical examination Blood tests, including tests for anemia or other abnormalities Thyroid testing when appropriate Assessment for infection Chest examination or chest X-ray when respiratory symptoms are present Sleep evaluation when sleep apnea or another sleep disorder is suspected Additional tests based on the patient's symptoms and medical history

Treatment

Treatment depends on the underlying cause. Management may include: Treating an underlying infection or medical condition Getting adequate sleep and regular rest Maintaining adequate fluid intake Eating a balanced and nutritious diet Gradually returning to physical activity as tolerated Managing stress Treating sleep disorders such as sleep apnea Adjusting medications when they contribute to fatigue, under medical supervision Following prescribed treatment for chronic lung conditions Antibiotics should only be used when a bacterial infection is diagnosed or strongly suspected and treatment is medically appropriate.

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Prevention

Fatigue cannot always be prevented, but the risk can sometimes be reduced by: Getting adequate and regular sleep Maintaining a balanced diet Drinking enough fluids Staying physically active within your abilities Managing chronic medical conditions Keeping recommended vaccinations up to date Practicing good hand hygiene Avoiding smoking and secondhand smoke Managing stress effectively Seeking medical care for persistent respiratory symptoms

Complications

Persistent fatigue can interfere with work, school, exercise and normal daily activities. It may also affect concentration, mood and quality of life. More importantly, unexplained or prolonged fatigue can sometimes be a sign of an underlying medical condition that requires treatment. Fatigue accompanied by significant breathing problems or other concerning symptoms should not be ignored.

When to See a Doctor

Consult a doctor if fatigue: Persists without an obvious explanation Is becoming progressively worse Interferes with normal daily activities Occurs with persistent cough or fever Occurs with shortness of breath or chest discomfort Is accompanied by unexplained weight loss or night sweats Continues after an infection has otherwise improved Is associated with dizziness, fainting or significant weakness Seek urgent medical attention for severe difficulty breathing, severe chest pain, fainting, confusion or a rapid deterioration in your condition.

Conditions Related to This Symptom

Learn more about medical conditions that may cause or be associated with this symptom.

Asthma
Asthma

Asthma is a chronic lung condition that causes inflammation and narrowing of the airways, making breathing difficult. Symptoms…

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Chronic Obstructive Pulmonary Disease (COPD)
Chronic Obstructive Pulmonary Disease (COPD)

Chronic Obstructive Pulmonary Disease (COPD) is a long-term lung disease that makes breathing difficult due to persistent…

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pneumonia
pneumonia

Pneumonia is an infection that causes inflammation of the air sacs (alveoli) in one or both lungs. The air sacs may fill…

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tuberculosis
tuberculosis

Learn about tuberculosis (TB), including symptoms, causes, diagnosis, treatment, prevention, recovery, and frequently asked…

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Frequently Asked Questions

Fatigue is a persistent feeling of tiredness, low energy or lack of physical and mental stamina. It can occur after an infection, with respiratory conditions or because of other medical problems.

Fatigue can have many causes, including respiratory infections, influenza, COVID-19, pneumonia, tuberculosis, COPD, asthma, poor sleep, sleep disorders, anemia, nutritional deficiencies, stress, dehydration and certain medications.

Yes. Respiratory infections such as influenza, COVID-19 and pneumonia can cause significant fatigue. Tiredness may continue for some time even after other symptoms begin to improve.

Yes. Chronic lung conditions such as COPD and poorly controlled asthma can contribute to fatigue. Breathing difficulties can make everyday activities require more effort and may reduce energy levels.

Yes. Tuberculosis can cause fatigue along with symptoms such as persistent cough, fever, night sweats and unexplained weight loss. Persistent or unexplained symptoms should be evaluated by a doctor.

Yes. Fatigue is a common symptom of COVID-19 and may occur with cough, fever, sore throat or shortness of breath. Some people may continue to experience fatigue after the initial infection.

You should consult a doctor if fatigue persists without an obvious explanation, becomes progressively worse, interferes with daily activities or occurs with symptoms such as persistent cough, fever, shortness of breath, chest discomfort, night sweats or unexplained weight loss.

A doctor may review your symptoms, medical history, sleep habits and medications and perform a physical examination. Depending on the suspected cause, blood tests, infection testing, chest imaging or sleep evaluation may be recommended.

Management depends on the underlying cause. Adequate sleep, sufficient fluids, a balanced diet, appropriate physical activity and stress management may help. Any underlying infection, lung condition or other medical problem should be treated appropriately.

Yes. Insufficient or poor-quality sleep can cause daytime fatigue, reduced concentration and low energy. Sleep disorders such as sleep apnea can also contribute to persistent fatigue.

Fatigue can occur during recovery from infections such as influenza, COVID-19 and pneumonia. However, fatigue that is severe, persistent or worsening should be discussed with a healthcare professional to rule out complications or another underlying condition.

Fatigue itself is not usually an emergency, but urgent medical attention is needed if it occurs with severe difficulty breathing, severe chest pain, fainting, confusion, significant weakness or a rapid deterioration in your condition.

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