While there are many causes of shortness of breath, the most common causes are lung disease, heart disease, or deconditioning (lack of exercise, especially in people who are overweight or obese).

Shortness of breath, medically known as "dyspnea," is most commonly caused by conditions affecting either the heart or the lungs, as these organs are responsible for transporting oxygen to your tissues and removing carbon dioxide. In 2026, the most frequent chronic causes include asthma, Chronic Obstructive Pulmonary Disease (COPD), and heart failure. In acute or sudden cases, the cause is often a chest infection like pneumonia, a severe allergic reaction, or even high levels of anxiety/panic attacks. Additionally, being significantly deconditioned or "out of shape" can cause breathlessness during minor exertion as the muscles demand more oxygen than the sedentary cardiovascular system can efficiently provide. While less common, more serious causes can include a pulmonary embolism (blood clot) or a heart attack. If shortness of breath occurs suddenly or is accompanied by chest pain, medical professionals in 2026 advise seeking emergency care immediately.