Which GLP-1 Has the Fewest Side Effects

GLP-1 Side Effects Compared, Drug by Drug

Digestive side effect rates differ across individual product labels, but these clinical trial numbers cannot be directly compared to rank one drug against another.

Every product package insert carries a clear comparability caveat. Adverse reaction rates observed in the clinical trials of one drug cannot be directly compared to rates in the clinical trials of another drug. Trials differ in patient populations, ranging from adults with obesity to people with type 2 diabetes. Study lengths range from about 24 to 72 weeks. Dose escalation schedules and target doses also vary. The table below summarizes adverse event rates from placebo-controlled trials published in each medication's official prescribing information.

*Note: In the 72-week Wegovy 7.2 mg trial, the 2.4 mg arm reported 35% nausea, 16% vomiting, and 19% constipation. n/a means the label does not give this figure.

In the STEP 1, 2, and 3 clinical trial pool lasting 68 weeks, 73% of participants on Wegovy 2.4 mg experienced at least one gastrointestinal adverse reaction, compared to 47% on placebo. Overall, 6.8% of patients stopped Wegovy due to any adverse reaction compared to 3.2% on placebo, while 4.3% discontinued specifically due to gastrointestinal reactions versus 0.7% on placebo.

Wegovy has also been tested at 7.2 mg weekly. In those 72-week studies, nausea was reported in 39% of patients, compared to 35% in the 2.4 mg arm and 13% in the placebo group. Vomiting occurred in 22% on 7.2 mg compared to 16% on 2.4 mg and 6% on placebo. Constipation reached 20% on 7.2 mg, 19% on 2.4 mg, and 8% on placebo. Dysesthesia, which is altered skin sensation, occurred in 22% of patients taking 7.2 mg, compared to 6% on 2.4 mg and 0% on placebo.

The Zepbound prescribing information pools data from the SURMOUNT-1 and SURMOUNT-2 trials up to 72 weeks. Across the 5 mg, 10 mg, and 15 mg doses, any gastrointestinal adverse reaction occurred in 56% of patients at each dose level, compared to 30% on placebo. Discontinuation due to adverse reactions was 3.4% on placebo versus 4.8% on 5 mg, 6.3% on 10 mg, and 6.7% on 15 mg.

Saxenda (liraglutide) is a daily injection. In 5 adult trials of 32 to 56 weeks, 9.8% stopped Saxenda because of adverse reactions, compared to 4.3% on placebo.

The Head-to-Head Evidence

Only a head-to-head trial compares two drugs in the same people over the same weeks.

Separate labels cannot show which drug is better tolerated. Two trials compared semaglutide and tirzepatide directly.

The primary trial comparing both drugs for weight loss is the SURMOUNT-5 trial, published in 2025. This open-label study enrolled 751 adults with obesity and no diabetes over 72 weeks. Patients received either tirzepatide at their maximum tolerated dose of 10 mg or 15 mg, or semaglutide at their maximum tolerated dose of 1.7 mg or 2.4 mg. Over the 72-week period, average weight change was -20.2% on tirzepatide compared to -13.7% on semaglutide. The most common adverse events in both groups were gastrointestinal, described as mostly mild to moderate, and occurred primarily during dose escalation.

The posted trial results on ClinicalTrials.gov for SURMOUNT-5 detail specific gastrointestinal rates across 374 patients on tirzepatide and 376 patients on semaglutide:

• Nausea: 43.6% on tirzepatide vs 44.4% on semaglutide.
• Diarrhea: 23.5% on tirzepatide vs 23.4% on semaglutide.
• Constipation: 27.0% on tirzepatide vs 28.5% on semaglutide.
• Vomiting: 15.0% on tirzepatide vs 21.3% on semaglutide.
• Gastroesophageal reflux disease (GERD): 6.1% on tirzepatide vs 10.6% on semaglutide.
• Eructation (burping): 9.9% on tirzepatide vs 7.7% on semaglutide.
• Alopecia (hair loss): 8.3% on tirzepatide vs 6.1% on semaglutide.

These findings show that nausea, diarrhea, and constipation rates were nearly even between the two medications. Semaglutide caused more vomiting and acid reflux. Tirzepatide produced slightly higher rates of burping and hair loss.

Earlier direct evidence came from the SURPASS-2 trial, published in 2021. This 40-week open-label trial evaluated 1,879 people with type 2 diabetes. Researchers compared tirzepatide at doses of 5 mg, 10 mg, and 15 mg against semaglutide dosed at 1 mg weekly. Nausea occurred in 17% to 22% of patients taking tirzepatide compared to 18% taking semaglutide. Diarrhea occurred in 13% to 16% on tirzepatide versus 12% on semaglutide. Vomiting was reported in 6% to 10% on tirzepatide compared to 8% on semaglutide. You can explore how these compounds compare further in our tirzepatide vs semaglutide review and see dose-by-dose rates in our Zepbound side effects guide.

Why Dose Matters More Than Brand

Each label reports its side-effect rates dose by dose, so dose is the comparison a label can support.

Within most labels, nausea and vomiting rise with dose. On Rybelsus, nausea climbed from 6% on placebo to 11% on 7 mg and 20% on 14 mg. Vomiting increased from 3% on placebo to 6% on 7 mg and 8% on 14 mg. On Trulicity, nausea rose from 5.3% on placebo to 12.4% on 0.75 mg and 21.1% on 1.5 mg, while vomiting increased from 2.3% to 6.0% and 12.7%. On Foundayo, nausea increased from 10% on placebo to 26% on 5.5 mg, 34% on 9 mg, and 35% on 17.2 mg. Vomiting on Foundayo similarly escalated from 4% on placebo to 13%, 21%, and 24%.

This pattern does not apply identically to every single symptom across every drug. For example, in the Zepbound trial pool, constipation was reported in 17% of patients on 5 mg, but dropped to 14% on 10 mg and 11% on 15 mg. Nausea on Zepbound was 25% on 5 mg, 29% on 10 mg, and 28% on 15 mg.

Every prescribing label links gastrointestinal reactions directly to dose escalation. Most adverse events occur during the initial escalation phase and decrease over time as the body adapts. The Wegovy label notes that prescribers may consider delaying dose escalation by 4 weeks if a patient does not tolerate a specific step. The Saxenda label advises that dose escalation can be delayed by about one additional week if an increase is not tolerated. Readers comparing daily liraglutide to weekly options can examine our Saxenda vs Wegovy analysis and Saxenda vs Zepbound comparison.

Pills vs Injections

Taking a pill instead of an injection does not remove digestive side effects.

The Wegovy label says its 25 mg tablet caused side effects similar in type and frequency to the injection. Rybelsus and Foundayo have their own label rates, below.

Rybelsus contains oral semaglutide and is labelled for type 2 diabetes only. Rybelsus must be taken on an empty stomach. In placebo-controlled diabetes trials, 8% of patients taking the 14 mg dose stopped treatment due to gastrointestinal adverse reactions, compared to 1% taking placebo. Nausea reached 20% on 14 mg, and vomiting reached 8%. For a direct comparison between oral and injectable semaglutide, read our Rybelsus vs Ozempic comparison.

Oral semaglutide has also been studied at higher doses for weight management. In a 64-week trial evaluating a 25 mg daily Wegovy tablet, 6.9% of patients stopped treatment due to adverse reactions, compared to 5.9% on placebo. Discontinuations due specifically to gastrointestinal events occurred in 3.4% of tablet patients versus 2.0% on placebo. The prescribing label notes that the types and frequency of adverse reactions were similar to the injection table, although per-symptom rates are not separately published. See our GLP-1 pill side effects guide for more details on tablet regimens.

Foundayo is a daily pill with its own prescribing label. Unlike Rybelsus, Foundayo is taken with or without food. In two clinical trials lasting up to 72 weeks, Foundayo's GI rates were above placebo at every dose. At the highest dose of 17.2 mg, nausea reached 35%, constipation was 24%, diarrhea was 25%, and vomiting reached 24%. Discontinuations due to gastrointestinal events occurred in 6% of patients on the 9 mg and 17.2 mg doses, compared to 0.7% on placebo. To evaluate how this oral agent compares against weekly injections, review our Foundayo vs Wegovy comparison and Foundayo vs Zepbound breakdown.

How to Choose if Side Effects Are Your Main Worry

No GLP-1 lets you skip digestive side effects. Two findings can still shape the conversation with your prescriber:

• If vomiting or reflux is your main worry: in SURMOUNT-5 vomiting (15.0% vs 21.3%) and GERD (6.1% vs 10.6%) were less common on tirzepatide; it is one open-label trial, so raise it with your prescriber rather than treating it as a ranking.
• If you want room to slow down: the Wegovy label lets a prescriber delay escalation 4 weeks; Saxenda about one extra week.

This comparison does not apply directly to patients with type 2 diabetes evaluating lower-dose regimens. Those rates come from lower-dose diabetes trials, such as semaglutide 1 mg in SURPASS-2 and Trulicity 0.75 mg and 1.5 mg, so they do not carry over to weight-loss doses. Patients managing diabetes should review our Zepbound vs Trulicity comparison and Rybelsus vs Ozempic guide.

A new head-to-head trial with different side-effect results would change this answer. Your own history can too: a person who vomited on semaglutide may do better on a different drug, and in SURMOUNT-5 vomiting and reflux were less common on tirzepatide.

Talk to your prescribing clinician about starting at the lowest available dose and review our GLP-1 side effects management guide to prepare for your titration schedule.

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