So here's the thing about oral semaglutide — the pharmacology is quite different from injectable even though it's the same molecule. Let me break down the key differences:
| Parameter | Injectable (Wegovy/Ozempic) | Oral (Rybelsus) |
|---|---|---|
| Bioavailability | ~89% | ~1% (yes, one percent) |
| Max approved dose | 2.4mg (Wegovy) | 14mg (Rybelsus) |
| Dosing frequency | Once weekly | Once daily |
| Food restrictions | None | Must take fasting, 30 min before food/drink |
| Steady-state serum levels | Achieved ~4-5 weeks | Achieved ~4-5 weeks |
| Primary indication | T2D + obesity | T2D only (14mg) |
The ~1% oral bioavailability is not a typo. Semaglutide is a peptide, and peptides are generally destroyed in the GI tract. Rybelsus uses a special absorption enhancer called SNAC (sodium N-[8-(2-hydroxybenzoyl)amino]caprylate) that protects the molecule and promotes absorption in the stomach.
Despite the low bioavailability, at the 14mg oral dose, you can achieve plasma levels roughly equivalent to injectable 0.5-1.0mg — but NOT equivalent to the higher weight management doses (1.7-2.4mg). This is the fundamental limitation.