Shortness of breath becomes an emergency when it comes on suddenly, is severe, or occurs at rest. Warning combinations include breathlessness with chest pain or pressure, a fast or irregular heartbeat, blue or grey lips or fingertips, or being too breathless to speak in full sentences. These can indicate a heart attack, heart failure, severe asthma attack, pneumonia, or a blood clot in the lungs.
People with asthma or COPD should treat a flare that does not respond to their usual reliever inhaler as urgent. Sudden breathlessness with calf pain or swelling, or that begins after long travel or surgery, raises concern for a pulmonary embolism and needs immediate care.
Gradual breathlessness over weeks, while less acutely dangerous, still deserves a medical review to find the cause. If breathing difficulty is severe, sudden, or worsening, call your local emergency number rather than booking a routine or online appointment.