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What to do if…
one leg suddenly becomes swollen, painful, or warm and you fear a blood clot

Produced and maintained by PanicStation.org Published: Last reviewed: Editorial policy USA guide

Short answer

Contact a healthcare provider right away and ask where you can be assessed promptly for a possible deep vein thrombosis. Call 911 immediately if you have difficulty breathing, chest pain, coughing up blood, lightheadedness, fainting, or a fast or irregular heartbeat.

Do not do these things

  • Do not delay seeking medical care because the symptoms seem mild or you are unsure what caused them.
  • Do not assume the symptoms are only a cramp, muscle injury, skin infection, or ordinary swelling.
  • Do not rely on a home check or symptom comparison to rule out a blood clot.
  • Do not start, stop, or change medication to treat a possible clot unless a healthcare professional tells you to.
  • Do not take leftover blood thinners or medication prescribed for someone else.
  • Do not drive yourself if you have chest pain, breathing difficulty, lightheadedness, or feel faint; call 911.

What to do now

  1. Check for difficulty breathing, chest pain or discomfort, coughing or coughing up blood, lightheadedness, fainting, or a fast or irregular heartbeat. Call 911 immediately if any of these are present.
  2. If you have only the leg symptoms, call your healthcare provider right away. Say that one leg has suddenly become swollen, painful, or warm and that you are concerned about a deep vein thrombosis.
  3. Ask where you can receive prompt medical assessment and any necessary testing. If you cannot obtain prompt medical advice or evaluation, go to an emergency department.
  4. Note when the symptoms began, where the pain or swelling is, and whether the skin is red or discolored. Do not delay care to monitor the leg for longer.
  5. Tell the healthcare professional about recent surgery, hospitalization, injury, limited movement, long travel, pregnancy, recent childbirth, estrogen-containing medication, cancer treatment, a previous blood clot, or a family history of blood clots.
  6. Take your medication list and identification with you. While arranging care, keep your phone nearby and call 911 if breathing problems, chest pain, coughing up blood, lightheadedness, or fainting begin.

What can wait

You do not need to work out the cause, choose a treatment, buy compression stockings, change regular medication, arrange specialist care, or make long-term travel and exercise plans now. The immediate task is obtaining prompt medical assessment.

Important reassurance

Several conditions can cause symptoms similar to deep vein thrombosis, so swelling, pain, or warmth does not confirm that you have a blood clot. Special medical tests are needed to diagnose or rule out a clot, and seeking prompt assessment is the appropriate next step.

Scope note

This guide covers immediate first steps only. Testing, treatment, medication decisions, and later prevention planning may require advice from qualified healthcare professionals.

Important note

This is general health information, not a diagnosis or a substitute for professional medical advice. Call 911 for emergency symptoms and seek prompt medical assessment for new, unexplained swelling, pain, or warmth in one leg.

Additional Resources

Closely connected guides that may be useful during the same situation or its immediate aftermath.

About this guide

This guide was produced and is maintained by PanicStation.org using its published editorial process. Official and specialist sources are checked where relevant, and AI-assisted tools may be used for drafting, organisation, and consistency checks. The site operator remains responsible for publication, revision, and removal decisions.

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