Pulled calf muscle vs blood clot: how to tell?

This is one of the genuinely important lookalike pairs, because one is a nuisance and the other can kill. A pulled calf (strain): you usually felt it happen, a pop or sharp pain during a run, a jump, a sudden push-off; it hurts with movement and stretching, you can pinpoint the sore spot, it may bruise over days, and it improves steadily with rest. A deep vein thrombosis (DVT): swelling of one calf or leg (measure around both; asymmetry is the clue), warmth over the area, an aching, cramping, or heavy pain that persists at rest (not just with use), sometimes skin redness or visible surface veins, and no injury story at all, per MedlinePlus. The risk context that raises clot suspicion: recent long travel or bed rest, surgery in the past weeks, cancer, estrogen (birth control pills, pregnancy, HRT), smoking, obesity, previous clots, or a family history of them. The dangerous wrong move: assuming it is a strain and massaging or stretching it, because a clot dislodged travels to the lungs. The pulmonary embolism signs that mean 911, not an appointment: sudden shortness of breath, sharp chest pain that worsens with deep breaths, racing heart, coughing blood, faintness. The same-day rule: one calf swollen, warm, and aching without an injury story is same-day medical evaluation, where an ultrasound settles it in minutes; do not wait days to see if it resolves. While awaiting evaluation: keep the leg still-ish, no massage, hydrate. The pulled-calf care, if that is what it is: RICE (rest, ice, compression, elevation), gentle stretching only after the acute days pass, and gradual reload, with a doctor visit if you cannot bear weight at all or it is not improving over 1 to 2 weeks.