What does shortness of breath feel like with blood clots in cancer?

A clot affecting blood flow through the lungs may cause sudden breathlessness, sharp chest pain that worsens with a deep breath, a fast heartbeat, dizziness, or a feeling of fear. You may also notice a cough, sometimes with blood, or pain and swelling in one leg if a clot has formed there. Cancer, treatment, infection, anaemia, and heart or lung problems can all affect breathing, so the symptom needs prompt clinical assessment rather than self-diagnosis.

If new breathlessness develops during cancer treatment or recovery, stop exertion and sit upright. Contact your oncology team or urgent medical service immediately for sudden symptoms, especially with chest pain, a racing heartbeat, faintness, or coughing blood. Do not massage a swollen painful leg, take unprescribed blood-thinning medicine, or wait to see whether severe symptoms pass.

Call emergency services for severe or rapidly worsening breathlessness, fainting, confusion, blue or grey lips, chest pain, coughing blood, or a very fast heartbeat with weakness. Tell responders that you have cancer or are receiving cancer treatment and describe when the breathing problem began. Do not drive yourself if you are seriously unwell.

Ask which symptoms require immediate hospital assessment, how your cancer treatment affects clot risk, what medicines you should take if a clot is confirmed, and who to call outside clinic hours.