How oral semaglutide survives the stomach: SNAC explained

The problem of oral semaglutide absorption comes down to one awkward fact: semaglutide is a peptide, a chain of amino acids with a fatty-acid side chain, and the stomach exists to take molecules like that apart. Swallowed on its own, almost none would reach the bloodstream, which is why the original Wegovy is an injection. The Wegovy pill gets around this by pairing semaglutide with an absorption enhancer called SNAC (salcaprozate sodium), which changes the conditions in a small patch of the stomach for just long enough to let a little of the drug through.

This guide explains what SNAC does, how much of a dose actually gets in, and why that one number accounts for every rule on the leaflet. It is information only, not medical advice: the Wegovy pill is a prescription-only medicine, and a prescriber decides whether it is suitable for you.

Oral semaglutide absorption: what SNAC actually does

SNAC (sodium N-[8-(2-hydroxybenzoyl)amino]caprylate, or salcaprozate sodium) is the absorption enhancer co-formulated with semaglutide in every Wegovy tablet; the SmPC lists it and magnesium stearate as the only other ingredients. According to the European Medicines Agency's assessment report, the 25 mg tablet contains 300 mg of SNAC, the amount used throughout the clinical trial programme, while the 1.5 mg, 4 mg and 9 mg tablets are a newer formulation that contains less. The report describes two actions, both local and both short-lived:

• It raises the pH around the tablet. In laboratory tests with small volumes of simulated gastric fluid, SNAC took the fluid from acidic to neutral within 5 to 15 minutes. Pepsin, the stomach's protein-digesting enzyme, is most active in acid, so a brief neutral pocket beneath the tablet protects semaglutide while it is absorbed.
• It makes the stomach lining temporarily more permeable. SNAC incorporates into cell membranes and increases their fluidity, letting semaglutide pass through the cells of the gastric lining rather than between them. In tissue studies the effect was already fading, back towards normal, within about an hour.

The upshot is unusual for a tablet: absorption happens mainly in the stomach rather than the intestine, and only very close to where the tablet is disintegrating. The EMA adds that semaglutide is broken down rapidly in intestinal fluid, so there is no safer stretch of gut further along. The UK Summary of Product Characteristics (SmPC) is careful about how settled this is, saying salcaprozate sodium facilitates absorption “based on in vitro data”.

How much of a dose actually gets in

Not much. The SmPC estimates absolute bioavailability at approximately 1–2%: of every hundred units swallowed, roughly one or two reach the circulation. That figure unlocks the dose numbers that confuse people. A 25 mg daily tablet is not ten times “stronger” than a 2.4 mg weekly injection; the SmPC reports similar average steady-state blood levels for the two (about 77 versus 75 nmol/L). Our pill vs injection page takes that comparison further.

What the tablet cannot match is the injection's consistency. The SmPC notes that 90% of patients on the tablet had average concentrations between 27 and 186 nmol/L, against 51 to 110 nmol/L on the injection, and the EMA's assessors wrote that absorption “is highly variable and may be minimal”. Peak levels arrive about an hour after a dose, and with a half-life of around a week, levels reach a steady state after four to five weeks. Taking the tablet the same way every morning is what the SmPC asks for: daily dosing as prescribed, together with that long half-life, reduces day-to-day fluctuation in exposure, and it says adherence to the dosing regimen is recommended for the best effect.

Why every rule on the leaflet follows from the chemistry

Once you know that absorption is low, local and fragile, the instructions stop looking fussy and start looking inevitable.

• Empty stomach, after at least 8 hours without food. The SmPC states that food decreases absorption; the EMA calls the reduction marked.
• No more than half a glass of water (about 120 mL). In a study in the EMA report, 240 mL of water rather than 120 mL cut exposure by roughly 40%. If absorption happens only beside the disintegrating tablet, a small volume keeps the tablet and its SNAC in one place.
• Wait at least 30 minutes before eating, drinking or taking other medicines. The SmPC notes that longer fasting before and after the dose gives higher absorption, and the MHRA's approval announcement says plainly that eating or drinking within 30 minutes lowers it. Our guide to the empty-stomach rule has practical ways to make the wait workable.
• Other tablets count too. In a trial reported in the SmPC, five other tablets taken alongside lowered total exposure by 34% and peak by 32%, attributed to multiple tablets being in the stomach at once.
• One tablet, swallowed whole. More than one tablet should never be taken to get a higher dose, and the leaflet says not to split, crush or chew it because it is not known whether this affects absorption. A missed dose is skipped, not doubled; our missed-dose guide explains why.

The dose steps up from 1.5 mg through 4 mg and 9 mg to 25 mg, with at least a month at each level, and the rules are the same at every step; the dosage page sets out the ladder.

Other medicines, sodium and breast-feeding

Three further points from the SmPC that come up once people start reading about SNAC:

• Acid-reducing medicines. The SmPC reports no clinically relevant change in semaglutide exposure when the tablet was taken with omeprazole.
• Levothyroxine. The SmPC notes that semaglutide delays stomach emptying, which may influence how other oral medicines are absorbed. It records a 33% rise in total thyroxine exposure, with the peak unchanged, after a single dose of levothyroxine, and says monitoring of thyroid parameters should be considered when the two are used together.
• Sodium and breast-feeding. The SmPC lists 23 mg of sodium per 25 mg tablet, about 1% of the WHO's recommended daily maximum, and describes the 1.5 mg, 4 mg and 9 mg tablets as essentially sodium-free. It also notes that salcaprozate sodium was found in breast milk, so the medicine should not be used while breast-feeding.

Side effects, Rybelsus and availability

The common side effects (nausea, diarrhoea, constipation, vomiting and headache) are the familiar effects of semaglutide, reported most often during dose escalation. The EMA assessed SNAC as a novel excipient with its own safety programme, and the SmPC describes the tablet's safety profile as consistent with the injection's, which contains no SNAC at all. Our side effects page covers the full list. If you experience a side effect from any medicine, report it through the MHRA Yellow Card scheme and speak to your GP or pharmacist.

Oral semaglutide with SNAC first came to market as Rybelsus, the tablet for type 2 diabetes, and the EMA notes that the Wegovy tablet strengths are identical in formulation to their respective Rybelsus strengths. They remain separate licensed products with separate dose ladders; our development page covers where the technology came from and the FAQ untangles the two. At the time of writing (October 2026) the Wegovy pill is available in the UK only on private prescription, following MHRA approval on 11 June 2026; NHS use would need a NICE appraisal. Private prices vary between regulated providers, so compare carefully and use only a GPhC-registered pharmacy or CQC-regulated clinic. For the wider picture, start at our home page or read how the Wegovy pill works.

Frequently asked questions

Related reading

• The Wegovy pill’s empty-stomach rule, and why it exists
• How the Wegovy pill works: oral semaglutide explained
• Wegovy pill dosage steps: 1.5 mg to 25 mg, month by month