Blood clots in the leg—known as deep vein thrombosis (DVT)—can be dangerous because they often form silently and may cause no symptoms until they break loose and travel to the lungs, creating a life-threatening pulmonary embolism. Still, there are warning signs people should watch for, including swelling, redness, warm skin, tenderness, rapid heartbeat, fever, distended veins, dizziness, or unexplained fatigue. In about half of all cases, no symptoms appear at all, making awareness even more important.

If a clot reaches the lungs, symptoms may escalate quickly into chest pain, shortness of breath, a racing heart, low blood oxygen, or fainting—signals that require immediate medical care. Long-term complications of DVT can also develop, such as post-thrombotic syndrome, which causes chronic pain, swelling, and skin changes.

One often-overlooked cause of clotting is high blood viscosity—thick, sticky blood that strains circulation and increases the risk for DVT, heart disease, and stroke. Staying hydrated, moving regularly, avoiding tight clothing, reducing sodium, quitting smoking, and getting enough omega-3s can all help lower risk. Awareness and early action are key to preventing serious consequences.