The short answer
Swelling has many causes, including a clot, an infection and lymphedema. Say clearly which side is affected and how fast it came on, and call your care team right away about new swelling in one limb.
Swelling with pain or tenderness, warmth, and red or discolored skin can be a deep vein thrombosis. CDC says to see a doctor as soon as possible. Call your care team right away.
Swelling with trouble breathing or chest pain needs emergency care, because a clot can travel to the lungs. Call 911.
Skin that is red, painful and warm can be cellulitis. MedlinePlus says to contact your provider right away.
NCI advises contacting your doctor as soon as you notice heaviness, swelling or tightness after lymph node surgery or radiation therapy.
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This page is for anyone with a swollen arm or leg who wonders if it could be cancer. It covers the common causes, the signs that need help fast, and what tests to expect.
One limb or both?
Start with the question a clinician will ask first. Is it one arm or leg, or both?
MedlinePlus says swelling can be all over the body or only in one part. Say which side it is when you call.
Clot signs: call your care team right away
CDC lists these symptoms of deep vein thrombosis (DVT), a blood clot in a deep vein:
- swelling.
- pain or tenderness.
- warmth.
- redness or discolored skin.
DVT most often affects the legs, but CDC and MedlinePlus say it can happen in an arm. CDC says to see a doctor as soon as possible if you have these signs. Call your care team right away. Do not wait to see if it settles.
Call 911 or go to the nearest emergency department if swelling comes with trouble breathing, chest pain or coughing up blood. CDC says to get medical help immediately for these signs of a clot in the lungs (pulmonary embolism). Do not drive yourself.
Call 911 or go to the nearest emergency department if the limb turns suddenly cold, pale or blue and very painful.
Call 911 or go to the nearest emergency department for sudden confusion or being hard to wake.
If you are on chemotherapy or have low white blood cells, call your care team right away, day or night, for chills, sore throat, mouth sores, burning when you urinate, redness at a catheter site, or any sign of infection. A normal temperature is not a reason to wait.
When the skin is red and warm
Cellulitis is a skin infection. MedlinePlus lists red skin that gets bigger, pain or tenderness, warm skin, and sometimes fever with chills. It says to contact your provider right away if you have symptoms of cellulitis. Treatment is usually antibiotics.
Call 911 or go to the nearest emergency department if the skin infection comes with confusion, a very fast heartbeat, shaking chills or cold, clammy skin.
Everyday reasons limbs swell
MedlinePlus lists causes of swelling that include:
- heart failure.
- kidney disease.
- liver disease.
- pregnancy.
- some medicines, including corticosteroids and some medicines for heart disease, high blood pressure or diabetes.
- sitting in one position for too long, such as a long flight or car ride, or bed rest (these raise clot risk).
MedlinePlus advises contacting your provider about any unexplained swelling.
Lymphedema after cancer treatment
If you have had lymph nodes removed or radiation therapy, lymphedema is a real possibility. NCI describes:
- a heavy, full or tight feeling in the area.
- swelling that may leave a dent when pressed.
- numbness or tingling.
NCI's advice is direct: contact your doctor as soon as you notice heaviness, swelling or other signs, because lymphedema is easier to control when treatment starts early.
NCI also says cellulitis is a common complication of lymphedema. If you have a fever or other signs of cellulitis, call your doctor right away.
Ultrasound and the rest of the workup
MedlinePlus says testing for DVT usually includes a Doppler ultrasound of the area. A D-dimer blood test or other imaging may also be used. NCI says doctors can use ultrasound to find a blood clot that might be causing swelling.
Details worth writing down
Note the date the swelling started and how quickly it grew. Record whether it dents when pressed and whether the skin is warm.
Add recent flights, surgery, bed rest, hormone medicines, and any past lymph node surgery or radiation therapy. Lymphedema covers day-to-day management if that turns out to be the cause.
Sources
Common questions
Does arm or leg swelling mean I have cancer?
Not always. MedlinePlus lists many causes of swelling, including heart failure, kidney disease, liver disease, pregnancy and some medicines. A clinician needs to look at the full picture.
How long should I wait?
Call your care team right away about new swelling in one limb. Call 911 or go to the nearest emergency department for swelling with trouble breathing or chest pain, or a limb that turns cold, pale or blue.
What should I bring to the visit?
Bring which limb swelled and when, whether it is one side or both, photos if you have them, recent travel, surgery or immobility, your medicines including hormones, and any history of lymph node surgery or radiation therapy.
Questions to ask your doctor
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Sources last checked: 2026-08-09 what this meansLast updated: 2026-09-29Next planned review: 2027-07-20
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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