GLP-1 Side Effect Rates: What Our Database's Own Clinical Evidence Shows

Ask "how common is nausea on semaglutide?" and most answers online repeat one number from one trial's package insert. Magistra's real-world evidence database instead pools every clinical trial and regulatory rate we've found that's independently sourced and citable, weights it by sample size and evidence quality, and computes a rate with a proper confidence interval — the same computation our predictor tool runs live. As of 22 August 2026, 13 of the 15 GLP-1 side effects we track clear the bar for this corpus-derived estimate. The other 2 fall back to a fixed published-literature range, which we label as a fallback rather than blend in silently.

This is the clinical track only — trial registries and regulatory sources, never patient self-reports. We track how often patients themselves mention each effect separately, as a *reporting frequency*, and never average the two together (a mention rate and an incidence rate measure different things). This article is about the clinical number only; the community track's own numbers are here, with definitions in our methodology.

The 13 corpus-derived rates (as of 22 August 2026)

"Rates / sources" is the eligible rate-point count and, after collapsing to one entry per distinct source (so one paper stating several rates can't out-vote five independent studies), the count our confidence label is actually based on. Every figure is served live at the link beside it — the numbers above are a same-day snapshot; check the API for the current value, since the corpus updates daily.

The 2 that still use a fixed literature range

These aren't corpus figures — they're the same fixed, published-literature dose-response reference the predictor falls back to whenever an effect has no eligible clinical data yet. We label them "Clinical (literature)" everywhere they appear, specifically so they're never mistaken for our own pooled estimate. Full detail in our data explorer.

Why some of these confidence intervals are wide

A few rows above have wide ranges — vomiting spans 0–98%, acid reflux spans 0–92%. That isn't a mistake or a rounding artefact; it's what happens when a handful of independent sources genuinely disagree on the rate (for vomiting, STEP-1's 500-patient semaglutide arm reports 5.3%, while a 10-participant early-phase oral GLP-1 study reports 40% — both are in the live source list at the API link above), and our method — a DerSimonian-Laird random-effects model, the standard approach for pooling heterogeneous studies — widens the interval to reflect that real disagreement rather than pretending the sources agree when they don't. A narrow interval built from 2-3 sources would be the false confidence; a wide one is the honest answer to "how sure are we." As more independent sources accumulate for an effect, the interval narrows — you can watch that happen over time at the live API.

The rule behind every number here

Every rate above passed the same three checks before it was allowed to count: it has to come from an external, linkable clinical trial or regulatory source (no self-citations, no news aggregator results); spontaneous adverse-event report shares (FAERS) are tracked separately and never blended into an incidence estimate; and a single paper stating multiple rates collapses to one vote. Full detail on the eligibility rule and which effects don't yet clear the higher bar needed for a fully calibrated statistical model is in our companion piece on evidence strength.

See the complete picture — all 15 effects, both tracks, live counts and every source — at magistra.health/en/data-api.