Sudden shortness of breath, or breathing difficulty (dyspnoea), is the most common reason for visiting a hospital accident and emergency department.
It's also one of the most common reasons people call 999 for an ambulance.
It's normal to get out of breath when you've overexerted yourself, but when breathlessness comes on suddenly and unexpectedly, it's usually a warning sign of a medical condition.
The information below outlines the most common reasons for:
This guide shouldn't be used to self-diagnose your condition, but should give you an idea of what's causing your breathlessness.
You should call your GP immediately if you have sudden shortness of breath, as there may be a problem with your airways or heart.
Your GP will assess you over the phone, and may either visit you at home or admit you to hospital.
If your shortness of breath is the result of anxiety, you may be asked to come to the surgery rather than having a home visit.
If you've struggled with your breathing for a while, don't ignore it. See your GP as it's likely you have a long-term condition that needs to be managed properly, such as obesity, asthma or chronic obstructive pulmonary disease (COPD).
Your doctor may ask you some questions, such as:
Feeling like you can't get enough air can be terrifying, but doctors are well trained in managing this. You may be given extra oxygen to breathe if this is needed.
Sudden and unexpected breathlessness is most likely to be caused by one of the following health conditions. Click on the links below for more information about these conditions.
Sudden breathlessness could be an asthma attack. This means your airways have narrowed and you'll produce more sticky mucus (phlegm), which causes you to wheeze and cough.
You'll feel breathless because it's difficult to move air in and out of your airways.
Your GP may advise you to use a spacer device with your asthma inhaler. This delivers more medicine to your lungs, helping to relieve your breathlessness.
If you have COPD, it's likely your breathlessness is a sign this condition has suddenly got worse.
In this case, shortness of breath may be the only warning sign you're having a heart attack. If you or your GP think this is the case, they'll give you aspirin and admit you to hospital straight away.
Heart failure can also cause breathing difficulties. This life-threatening condition means your heart is having trouble pumping enough blood around your body, usually because the heart muscle has become too weak or stiff to work properly. It leads to a build-up of water inside the lungs, which makes breathing more difficult.
A combination of lifestyle changes and medicines or surgery will help the heart pump better and relieve your breathlessness.
Breathlessness could also relate to a problem with your heart rate or rhythm, such as an irregular and fast heart rate (atrial fibrillation) or a regular and fast heart rate (supraventricular tachycardia).
A panic attack or anxiety can cause you to take rapid or deep breaths, known as hyperventilating. Concentrating on slow breathing or breathing through a paper bag should bring your breathing back to normal.
Long-term breathlessness is usually caused by:
More unusual causes of long-term breathlessness are: