Semaglutide vs Tirzepatide Side Effects Compared

Semaglutide and tirzepatide are the two most discussed GLP-1 class compounds, and the most common question people compare is tolerability. Both are associated mainly with gastrointestinal (GI) side effects, but the reported rates, the symptom mix, and how often people stop differ between them. This is a neutral, third-person summary of what published clinical trials report, with the numbers laid out side by side.

Nothing here is medical or dosing advice. Peptides are research compounds not approved for human consumption, and tolerability decisions belong to a licensed clinician. The goal is to help you read trial data, not act on it. To model the math behind a vial, use the tirzepatide calculator.

Why both compounds share the same side effect profile

Semaglutide is a single GLP-1 receptor agonist. Tirzepatide is a dual agonist that acts on both GIP and GLP-1 receptors. Despite that difference, the side effects reported in trials cluster in the same place: the gut. Slowed gastric emptying is the common thread, which is why nausea, vomiting, diarrhea, and constipation dominate the adverse event tables for each one.

Most GI events in trials are described as mild to moderate, appear early during dose increases, and decline as the body adjusts. The pattern is dose-dependent for both compounds, meaning faster or larger increases tend to track with more reports. For a week-by-week view of one compound, see the semaglutide side effects timeline and the tirzepatide side effects week by week.

GI symptom incidence side by side

The numbers below are approximate ranges drawn from large registration trials (the STEP program for semaglutide and the SURMOUNT and SURPASS programs for tirzepatide). Exact figures vary by trial, dose, and population, so treat these as reference ranges, not fixed values.

• Nausea: roughly 20 to 44 percent on semaglutide; roughly 12 to 33 percent on tirzepatide depending on dose.
• Diarrhea: roughly 20 to 30 percent on semaglutide; roughly 12 to 23 percent on tirzepatide.
• Vomiting: roughly 9 to 24 percent on semaglutide; roughly 6 to 13 percent on tirzepatide.
• Constipation: roughly 11 to 24 percent on semaglutide; roughly 6 to 17 percent on tirzepatide.
• Placebo nausea for context: often in the 8 to 16 percent range, showing not every reported symptom is drug-driven.

The headline pattern: across most trials the per-symptom rates land in a broadly similar band, with semaglutide often reporting nausea and vomiting at the higher end. Because the trials used different doses and titration speeds, a clean one-to-one comparison is not possible from this data alone.

Tolerability and titration

Tolerability in trials is shaped less by the compound itself and more by how fast the dose climbs. Both programs used slow, stepwise increases over months specifically to keep GI events manageable. When people compare the two and one feels harsher, the titration schedule and starting point are often the real variable, not the molecule.

Worked example of the math, not a recommendation: a 10 mg tirzepatide vial reconstituted with 0.5 mL of bacteriostatic water gives 20 mg/mL. A 2.5 mg reference dose would be 0.125 mL, which reads as 12.5 units on a U-100 insulin syringe. Run your own vial through the peptide dosage calculator so the unit number matches your concentration, not someone else's.

Discontinuation rates

Discontinuation due to adverse events is the cleaner tolerability signal because it captures symptoms people could not live with, not just symptoms they noticed. In the registration trials both compounds reported single-digit to low-double-digit discontinuation rates driven mainly by GI events.

• Semaglutide: adverse-event discontinuation commonly reported around 4 to 7 percent in the STEP weight trials.
• Tirzepatide: adverse-event discontinuation commonly reported around 4 to 7 percent in SURMOUNT and SURPASS, with some dose arms lower.
• Both: the large majority of participants who started completed the trials, and most GI events did not lead to stopping.

In head-to-head and pooled comparisons the discontinuation rates for the two compounds are broadly comparable, which is a key point: neither one stands out as dramatically harder to stay on at matched, slow titration. For a deeper feature comparison beyond side effects, see semaglutide vs tirzepatide and the focused side effects comparison.

How to read this if you are comparing

1. Match the dose step, not the milligram. Early titration doses drive most early symptoms for both.
2. Read symptom ranges, not single numbers. Trial-to-trial variation is wide.
3. Separate noticed from intolerable. Discontinuation rates matter more than raw symptom counts.
4. Confirm your own concentration before trusting any unit figure you see online.

Bottom line from the published data: semaglutide and tirzepatide share a GI-dominant side effect profile, report broadly similar per-symptom and discontinuation ranges, and are both managed largely through slow dose increases. Differences exist at the margins, but titration speed is the bigger lever in the trials. Any actual use decision belongs with a licensed clinician. See the full disclaimer.