---
title: "Semaglutide Side Effects Reported in STEP and SELECT"
url: https://www.primaralabs.com/answers/what-are-the-side-effects-of-semaglutide
source: Primara Labs, markdown mirror of the HTML page
---

# What are the side effects of semaglutide?

In STEP 3, a phase 3 trial of semaglutide (checked 23 September 2026), nausea was reported by 58.2% of participants against 22.1% on placebo, and constipation, diarrhoea and vomiting were also more frequent. In SELECT, the 17,604-person cardiovascular trial, 16.6% stopped semaglutide for adverse events against 8.2% on placebo.

Primara Labs sells some of the compounds covered here. Every figure on this page links to its source and the date it was checked.

Updated 23 September 2026

01

## STEP 3 and STEP 8

In STEP 3, discontinuation because of adverse events was 5.9% on 2.4 mg, against 2.9% on placebo. The most frequently reported adverse events were gastrointestinal adverse events in 82.8% on 2.4 mg against 63.2% on placebo, nausea in 58.2% on 2.4 mg against 22.1% on placebo, constipation in 36.9% on 2.4 mg against 24.5% on placebo and diarrhoea in 36.1% on 2.4 mg against 22.1% on placebo.

In STEP 8, discontinuation because of adverse events was 3.2% on semaglutide 2.4 mg and 12.6% on liraglutide 3.0 mg, against 3.5% on placebo (pooled). The most frequently reported adverse events were gastrointestinal disorders in 84.1% on semaglutide 2.4 mg and 82.7% on liraglutide 3.0 mg against 55.3% on placebo (pooled), nausea in 61.1% on semaglutide 2.4 mg and 59.1% on liraglutide 3.0 mg against 22.4% on placebo (pooled), constipation in 38.9% on semaglutide 2.4 mg and 31.5% on liraglutide 3.0 mg against 23.5% on placebo (pooled) and diarrhoea in 27.8% on semaglutide 2.4 mg and 18.1% on liraglutide 3.0 mg against 25.9% on placebo (pooled).

02

## SELECT

In SELECT, discontinuation because of adverse events was 16.6% on semaglutide 2.4 mg, against 8.2% on placebo.

03

## The outcomes they sit beside

In STEP 3, a phase 3 trial of semaglutide in US adults without diabetes with overweight (BMI 27 or greater) plus at least 1 comorbidity or obesity (BMI 30 or greater) (n=611), mean body weight fell 16.0% on 2.4 mg over 68 weeks, against 5.7% on placebo (treatment-policy estimand; Wadden TA et al. JAMA 2021 (STEP 3)).

In STEP 4, a phase 3 withdrawal trial (n=803), participants who continued semaglutide after a 20-week run-in lost a further 7.9% by week 68, while those switched to placebo regained 6.9%.

Sources

## Where every figure comes from

1.  [Wadden TA et al. JAMA 2021 (STEP 3)](https://doi.org/10.1001/jama.2021.1831) · checked 23 September 2026
2.  [Rubino DM et al. JAMA 2022 (STEP 8)](https://doi.org/10.1001/jama.2021.23619) · checked 23 September 2026
3.  [Lincoff AM et al. N Engl J Med 2023 (SELECT)](https://doi.org/10.1056/NEJMoa2307563) · checked 23 September 2026

Last reviewed 23 September 2026

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-   [STEP 8 on the Trial Explorer](https://www.primaralabs.com/research/trials/step-8)

-   [How does semaglutide work?](https://www.primaralabs.com/answers/how-does-semaglutide-work)
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