It is true that if the clot which has not propagated for two weeks is less likely to propagate. There is no absolute safety at this short time period. Also the clots in the calf veins as against the more proximal veins propagate even less. However one has to be sure that the diagnosis is correct, that there are no concomitant clots in other veins. It is also prudent to follow medical advice and discuss the clinical situation with the treating physician. If the thrombosis is proven then anti-coagulation should be given for a minimum period of 3 months, sometimes longer if the risk factors are known. In the query it was written that therapeutic level was never achieved. This calls for review of the treatment strategy and finding out if there are any antagonistic drugs or foods being consumed..
Coumadin lasts for a period of about a week gradually in reducing levels of INR..