Why can't Heparin be administered orally?

Haparin is a medication used to prevent and treat blood clots. It is administered by injection. Heparin can never be administered orally because it is large and negatively charged and cannot pass the membrane to be absorbed. Heparin has a wide variety of uses pertaining to blood clots.

It can be used to treat some clotting disorders, to prevent blood clots after surgery, during dialysis, during blood transfusions, when collecting a blood sample, or when a person is rendered unable to move for a long period of time. Heparin is known as an anticoagulant.