Symptom · Shortness of breath

Why am I short of breath?

Shortness of breath can come from the lungs, the heart, or other causes, and it ranges from mild to serious. Here is a plain-language overview and the warning signs that mean you should seek help urgently.

When breathlessness needs urgent care

Get emergency help if shortness of breath comes on suddenly and severely, happens at rest, or comes with chest pain, blue lips or face, confusion, or trouble speaking in full sentences. Breathing that suddenly becomes difficult is treated as an emergency because some causes need fast treatment.

Common causes of shortness of breath

Feeling short of breath can come from the lungs, such as asthma, a chest infection, or chronic lung disease, or from the heart, when it is not pumping as effectively. It can also follow anemia, anxiety, being very out of condition, or being at high altitude. Whether it came on over minutes, days, or months is an important clue to the cause.

What a clinician looks at

A clinician considers how quickly it started, what makes it better or worse, and any other symptoms, and may use tests such as oxygen levels, a chest X-ray, or blood tests. New, worsening, or unexplained breathlessness is worth having checked rather than pushing through.

What to consider next

Get emergency help for sudden or severe breathlessness at rest.
Note whether it came on over minutes, days, or weeks.
New or worsening shortness of breath is worth a medical review.

Think through your symptoms

Answer a short set of structured questions and Mednex gives a cited, plain-language read on what could be involved and what to consider next. It is educational and never a diagnosis.

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Common questions

When should shortness of breath be treated as an emergency?

When it comes on suddenly and severely, happens at rest, or comes with chest pain, blue lips, confusion, or an inability to speak in full sentences. Sudden difficulty breathing needs emergency care because some causes require fast treatment.

Can being unfit cause shortness of breath?

Yes, being out of condition can make you breathless with exertion, and this often improves with gradual activity. However, new or worsening breathlessness should not be assumed to be fitness alone, especially if it appears at rest or with other symptoms.

Can anxiety make me short of breath?

Anxiety and panic can genuinely cause breathlessness. Because the symptom has lung and heart causes too, it is safest to have new or unexplained shortness of breath assessed rather than assuming anxiety, particularly the first time.

Sources

MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); Breathing Problems; [cited 2026 Jul 14]. Available from: https://medlineplus.gov/breathingproblems.html
MedlinePlus Medical Encyclopedia [Internet]. Bethesda (MD): National Library of Medicine (US); Breathing difficulty; [cited 2026 Jul 14]. Available from: https://medlineplus.gov/ency/article/003075.htm

Content last reviewed 9 July 2026. Reference ranges vary by laboratory; always read your results against the range printed on your own report.

This page describes a common symptom in general terms using public information from the U.S. National Library of Medicine. It is educational and is not a diagnosis or medical advice, and it cannot tell you what is causing your symptom. If your symptom is severe, sudden, or does not go away, or if you are worried, contact a healthcare professional.