A Patient Who Is Newly Diagnosed with Type 1 Diabetes

A patient who is newly diagnosed with type 1 diabetes mellitus asks why insulin must be given by subcutaneous injection instead of by mouth. The nurse will explain that this is because

A) absorption is diminished by the first-pass effects in the liver.
B) absorption is faster when insulin is given subcutaneously.
C) digestive enzymes in the GI tract break down the drug and prevent absorption.
D) the oral form is less predictable with more adverse effects.