On an empty stomach, with restricted water, and nothing to eat afterwards for a while. That is not a preference. Absolute bioavailability is about 0.4% to 1% under those conditions, and in the fed state plasma concentrations stay below the limit of quantification [1]. A price page lists a tablet beside an injection as two ways to buy the same molecule. That is true and it hides the interesting part. The clinical result of the tablet is covered in what the 25 mg trial showed. This is the part underneath it.
The number
Absolute bioavailability of oral semaglutide is approximately 0.4% to 1%, under optimized fasting conditions with restricted water intake. So between roughly 99% and 99.6% of the tablet never reaches the bloodstream at all.
The injection does not have this problem. That is why the oral dose is so much larger than the injected one for the same molecule. The sizes differ because the routes differ, not because the products are different strengths of the same thing.
Where the rest goes
Four losses, according to the review. The peptide is broken down by enzymes in the gut. It crosses the gut lining poorly. The stomach’s own physiology limits what can be absorbed. And some of what survives is metabolized before it reaches circulation.
Peptides are food, structurally speaking. The digestive tract is extremely good at taking them apart, and getting one through intact is the whole engineering problem.
Food closes the window
In the fed state, the review reports, plasma semaglutide concentrations remain below the limit of quantification.
Not reduced. Not less effective. Unmeasurable. Whatever the instructions say about fasting and water, they are the difference between taking the drug and not taking it. A reader comparing a tablet to an injection on price alone is comparing two things that are not interchangeable.
What the dose has to be, because of all this
The trials show the size of the correction. Oral semaglutide at 25 mg over 64 weeks produced a mean weight reduction of 13.6% against 2.2% on placebo [2]. A 50 mg dose in 201 East Asian adults gave a mean reduction of 14.3% against 1.3% on placebo [3]. The injected doses for the same molecule are measured in single-digit milligrams.
Those two results are read separately in the 50 mg trial and against the injection in the pill against the needle. Neither is a reason to skip the fasting rules, because both were measured under them.
Variable, and stable anyway
Absorption swings a lot, between people and from day to day in the same person, and the usable dose range is narrow.
Steady-state levels still come out reasonably even. Semaglutide has a half-life of about a week and binds extensively to albumin, so a low day is buffered by the drug already in circulation. That is a real advantage of a long-acting molecule. It is also why a missed window does not announce itself.
Why this belongs on a disclosure site
Because the delivery system is part of what you are buying, and it is the part least likely to appear on a product page. A seller can publish a molecule, a format and a figure without ever saying what the tablet is formulated with or under what conditions the number was established.
That gap is the same one this site counts everywhere else — what gets published against what gets left out. Which sellers list formats at all is in the format finder, and what happens to price when the same molecule changes route is in the six-times-the-price comparison.