Lmwx 20 mg Injection 0.2 ml is used to prevent or treat blood clots caused by medical conditions, such as unstable angina, after an operation or long periods of bed rest due to illness, after a heart attack, and the formation of blood clots in the dialysis machine tubes. A blood clot is a mass of blood that forms when platelets, proteins, and cells in the blood stick together. A blood clot can occur in any body part, leading to a heart attack, stroke, and organ damage.