This is the version of the explanation I wish somebody had given me, written down before I forget what confused me. It is about oral semaglutide, and it is deliberately narrow — everything I am not confident about is marked as such.
What is actually established
Oral semaglutide is absorbed in the stomach with the help of SNAC, which locally raises pH and protects the peptide long enough to cross. That mechanism is fragile: bioavailability is roughly 1% and highly sensitive to gastric contents, so a mouthful of coffee genuinely changes the exposure. This is why the label wants 30 minutes and no more than half a glass of plain water.
The condition it depends on
The absorption variability is real, but it partly averages out over weeks — the steady-state trough is less erratic than any single day would suggest. Where it bites is in the first fortnight, when people conclude the tablet does nothing.
The practical version
The practical numbers: about 1% oral bioavailability, 30 minutes fasted before food, no more than 120ml of plain water, and coffee counts as food for this purpose.
What I am not sure about
The bit I cannot resolve on my own is how much of the oral variability is the SNAC absorption window and how much is dose, because the two get conflated constantly. I would rather have one careful answer than five confident ones.
amy_econ_NJ said:Oral semaglutide is absorbed in the stomach with the help of SNAC, which locally raises pH and protects the peptide long enough to cross.
amy_econ_NJ has the substance of this right. The condition it depends on is worth stating. Orforglipron is the more interesting oral story because it is not a peptide at all. Being a small molecule it does not need SNAC, does not need the fasting window, and has oral bioavailability in the tens of percent rather than about one.
amy_econ_NJ said:Oral semaglutide is absorbed in the stomach with the help of SNAC, which locally raises pH and protects the peptide long enough to cross.
I do not accept that the fasting window is a minor inconvenience. Adherence data on daily orals with timing requirements is consistently worse than weekly injections, and a drug you take imperfectly is a lower dose than the one on the box.
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View ResultsTaking the question as asked, rather than the general version of it. The OASIS programme put 50mg oral in the same territory as 2.4mg injectable — around 15% mean weight loss — but it needed a dose 20 times larger to get there because almost none of the tablet is absorbed. The dose numbers are not comparable across routes and quoting them side by side confuses people.
Dr.ObesityMed said:Orforglipron is the more interesting oral story because it is not a peptide at all.
Same pattern here, and in the same order. I had assumed I was the exception until I read this.