Acute DVT refers to a spontaneous or short-term blood clot. If the thrombus starts in your veins within the last 14 days or less, we classify it as acute DVT. Acute DVT is a potentially life-threatening condition if left untreated. It can travel in the vein system to the lungs as a pulmonary embolus. Without blood thinners, more clots can form and can become free floating and travel to the lungs as a lethal pulmonary embolus. Most acute cases are manageable with proper treatment since the thrombus will not harden or stick to your vein’s walls in this time frame. Some patients may experience subacute DVT, which is present in the body for 14-28 days. These cases are more severe than acute DVT, with greater chances of hardening or connecting to the veins.