Leg Swelling and Calf Pain: — Could It Be a Blood Clot?

Yes, and it is worth considering — but the pattern differs. A cramp usually eases within minutes to an hour. A strain follows exertion and improves steadily with rest over a day or two. What distinguishes DVT is that the swelling stays or worsens over several hours, the leg remains warm and tender to press, and it typically affects one leg only. If you are unsure after a few hours, call your team. Do not wait it out, because DVT can progress quickly.

Cancer itself makes the blood clot more easily as part of how the disease affects the body. Many chemotherapy drugs add to this by damaging the lining of blood vessels, which triggers the clotting process. Long periods of lying still or reduced movement during treatment also slow blood flow in the legs. NCCN and ASCO both identify cancer-associated thrombosis as one of the most significant complications during treatment — which is why any new one-sided leg swelling needs prompt assessment rather than a wait-and-see approach.

Most people do not have to stop. Treatment for DVT in cancer patients is usually a blood-thinning injection, and the majority continue chemotherapy alongside it. Your oncologist will decide based on how severe the clot is, which drugs you are on, and how your treatment is going overall. Do not stop or adjust any medication without speaking to your team first.

DVT most commonly causes swelling in one leg. Swelling in both legs is more often a sign of fluid retention from chemotherapy, low protein levels, or a heart- or kidney-related side effect — a different problem, but still worth reporting to your team. If both legs swell suddenly and you also feel breathless, unwell, or have chest pain alongside it, that still needs same-day emergency assessment.