A blood clot can start small and feel harmless — then become dangerous quickly. Knowing the common signs, main risk factors, and practical steps to prevent clots can save you from a medical emergency. This page gives clear, no-nonsense advice you can use right away.
Clots form when blood sticks together instead of flowing. They can happen in veins (deep vein thrombosis or DVT) or travel to the lungs (pulmonary embolism or PE). DVT often appears in a calf or thigh; PE is more serious because it blocks blood flow to the lungs and can be life-threatening.
Watch for sudden, new symptoms. For DVT, common signs are swelling in one leg, pain or tenderness (often in the calf), warmth, and redness along a vein. If you have sudden shortness of breath, chest pain that gets worse with deep breaths, rapid heartbeat, lightheadedness, or coughing up blood, call emergency services — those could be signs of PE.
Not all clots hurt or swell. If you have risk factors (see next section), take any new unexplained symptoms seriously and contact your doctor right away. Quick action matters: treatment works best when a clot is caught early.
Some risk factors you can change, some you can’t. Major, modifiable risks include long periods of sitting (flights, desk work), dehydration, smoking, obesity, and certain medications like some birth control pills or hormone therapy. Surgery, trauma, cancer, pregnancy, and a family history of clots are non-modifiable or temporary risks that need special attention.
Practical steps you can start today: move often — stand up and walk every hour if you sit most of the day; stay hydrated; avoid smoking; keep a healthy weight; and exercise regularly. When traveling, flex your ankles, walk when possible, and wear compression socks for long flights if your doctor recommends them.
If you’ll have surgery or you’re hospitalized, ask your care team about clot prevention. Hospitals often use blood thinners or compression devices to lower risk. People with a history of clots or certain medical conditions may need long-term blood thinners (like warfarin or direct oral anticoagulants). These drugs reduce clot risk but raise bleeding risk, so follow dosing and monitoring instructions closely.
Know who to talk to: your primary care doctor, a vascular specialist, or hematologist can assess your personal risk and suggest tests or medication. If you’re starting a new medication, pregnant, or planning surgery, mention any family history of clots.
Finally, trust your instincts. If something feels off — swelling, new unexplained pain, or sudden breathlessness — get medical attention. Quick care can stop a small clot from becoming a major problem.
