The Role of Oral Administration in Drug Absorption

Most drugs are given orally because they get digested in the gastrointestinal tract. Subcutaneous is basically injected into fat, but insulin's a protein or a peptide. You kind of want it to diffuse slowly over time and equate well to what you're putting in food-wise. The last thing you want to do is ingest a peptide either because the whole point of the stomach is to denature those peptides.