Foundayo Side Effects: What the Label Reports, by Dose

Foundayo's glp-1/restarting-a-glp1">side effects are gastrointestinal and dose-dependent. At the 17.2 mg maximum dose, 35% of patients reported nausea, 25% diarrhoea and 24% vomiting. The assumption behind reaching for a pill instead of an injection — that swallowing a drug must be gentler — does not survive the label, but neither does its opposite: Foundayo lands between two injections, worse than tirzepatide and better than semaglutide.

Every reaction, by dose

These come from a pool of both 72-week trials, 3,155 patients on Foundayo against 1,576 on placebo. The label lists every reaction that occurred in at least 5% of treated patients and more often than on placebo.

The form is not what decides it

Foundayo sits in the middle, not at either end. It is worse than injected tirzepatide and clearly better than injected semaglutide — Wegovy reports nausea in 44% of patients, nine points above the tablet.

Those figures come from different trials in different populations and are not a fair head-to-head, which is why the label itself warns against exactly this comparison. But the spread is wide enough to settle the underlying question: the route of administration is not what determines how a GLP-1 feels. If it were, the two injections would not sit at opposite ends of the range with the tablet between them. What determines it is the molecule and how hard it is pushing the receptor. Delivering a drug as a tablet solves the needle and nothing else.

Overall, gastrointestinal reactions of some kind affected 60% of patients on 5.5 mg, 68% on 9 mg and 69% on 17.2 mg, against 37% on placebo. Of those who reported any GI reaction, 60% described it as mild, 36% moderate and 4% severe.

Why the numbers stop rising at the top dose

Read the constipation row again: 20%, then 27% at 9 mg, then down to 24% at the maximum. Dyspepsia does the same, peaking at 16% on 9 mg and falling to 13%. It would be easy to read that as the drug becoming easier at higher doses. It is not.

Foundayo is titrated in five steps with at least 30 days at each. Anyone whose constipation was intolerable at 9 mg does not reach 17.2 mg to be counted there. The population in the last column has already been filtered by the middle ones, so the top-dose figures describe people who tolerated everything below it.

The practical consequence is that the middle columns, not the last one, describe what the climb feels like. And the label is explicit that nausea, vomiting and diarrhoea were most frequent during dose escalation and decreased over time.

How many people stop, and a number that looks contradictory

Across both trials, 8% of Foundayo patients stopped because of an adverse reaction — 6% at 5.5 mg, 9% at 9 mg, 10% at 17.2 mg — against 3% on placebo. Most of that was gastrointestinal: 3%, 6% and 6% by dose, against 0.7% on placebo.

If you have also read our page on the weight-loss results, you will have seen that more people left the placebo group than any Foundayo group — 30% against 22 to 24%. Both figures are in the label and they do not contradict each other. The 30% is people who stopped for any reason, and over 72 weeks the most common reason to abandon a trial is that nothing is happening. The 8% is people who stopped because of a side effect. Side effects are the more likely reason to quit the drug; futility is the more likely reason to quit the placebo.

The interaction almost nobody mentions

Foundayo can make oral contraceptives less reliable. It delays gastric emptying, which affects how other swallowed medicines are absorbed, and the label instructs anyone using an oral contraceptive to switch to a non-oral method or add a barrier method for 30 days after starting Foundayo, and for 30 days after every dose increase.

With five escalation steps, that is six separate 30-day windows spread across roughly the first six months. Non-oral hormonal contraception is not affected. This sits in a drug-interactions table rather than in the warnings, which is probably why it is missing from most coverage, and it is the most immediately actionable thing in the whole label.

Two other interactions are worth knowing. Simvastatin exposure roughly doubles, so the label caps it at 20 mg daily alongside Foundayo. And in people with type 2 diabetes taking a sulfonylurea, hypoglycaemia was reported in 7% against 0.5% of those not on one — the label advises considering a dose reduction of insulin or sulfonylurea when starting.

The serious risks

These come from the warnings rather than the incidence table.

• Thyroid C-cell tumours — a boxed warning, from rodent studies, shared with the whole GLP-1 class. Contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2.
• Pregnancy — may cause fetal harm; discontinue when pregnancy is recognised. Weight loss offers no benefit during pregnancy.
• Severe hepatic impairment — not recommended.
• Hypoglycaemia — 2% against 0.2% on placebo in the type 2 diabetes trial, and much higher alongside a sulfonylurea.

The general class picture, including how these compare with the injectables, is in the GLP-1 side effects timeline, and practical management in managing nausea on GLP-1. What Foundayo is and how it is dosed is covered in Foundayo explained.