The Antithrombin III blood test has quite a few other names, like, Functional Antithrombin III test or AT III test. When we bleed our body naturally prepares a defence mechanism that prevents excess blood loss. The process is known as clotting. There are clotting factors or proteins which regulate clotting and maintain blood flow into our blood vessels. Sometimes, abnormally high blood clotting or thrombosis can prove to be fatal because blood flow to the vital organs is obstructed. This is averted by Antithrombin which is a natural anticoagulant produced by the body. Antithrombin acts as a blood thinner and regulates blood clotting. If blood clotting happens abnormally or deep vein thrombosis occurs, then Antithrombin III test is ordered to check its level. The reference range for new born is 60% - 90%. For children and adults the range is 80% - 120%.
