Low molecular weight heparins (LMWH) have largely replaced unfractionated heparin. Their much more predictable anticoagulant response combined with high bioavailability after subcutaneous injection means that the dose can be calculated by body weight and given subcutaneously without any monitoring or dose adjustment. Their widespread use resulted in most patients with deep vein thrombosis being managed as outpatients, and this is also increasingly the case for uncomplicated pulmonary embolism....