Which explanation best describes why insulin cannot be taken orally, as commonly discussed in teaching sessions?

• A. Insulin cannot be manufactured in pill form
• B. Insulin is destroyed by gastric juices, rendering it ineffective
• C. Your health care provider decides the route of administration
• D. Your health care provider will prescribe pills when you are ready

Answer: (B)

Insulin is a protein hormone, so taking it by mouth faces a built-in obstacle: the digestive system is designed to break down proteins. The acidic environment in the stomach and digestive enzymes like proteases destroy the insulin molecule, altering its shape and disabling its ability to bind to receptors. Even if some intact insulin survived digestion, its large size and hydrophilic nature make it poorly absorbed through the intestinal lining, so only negligible amounts would reach the bloodstream in an active form. That’s why oral delivery wouldn’t work effectively, and injections are used to place insulin directly into circulation. Researchers are exploring protective formulations to enable oral delivery, but none are standard yet.