Semaglutide side effects by the numbers: STEP rates, placebo rates and when they happen

"Nausea is common" is not information. "44 out of 100 people on Wegovy 2.4 mg reported nausea at some point over 68 weeks, against 16 out of 100 on placebo" is. The tool above holds the label tables and does the subtraction. This page explains where each number comes from and what the trials say about timing.

The Wegovy 2.4 mg table

Table 3 of the Wegovy label pools the adult weight-reduction trials: 2,116 people on semaglutide 2.4 mg and 1,261 on placebo. Reactions reported by 2% or more and more often than placebo, semaglutide first:

In the same trials 6.8% of Wegovy patients and 3.2% of placebo patients permanently stopped for adverse reactions; nausea (1.8% vs 0.2%), vomiting (1.2% vs 0%) and diarrhea (0.7% vs 0.1%) led. Among people with type 2 diabetes not on insulin, hypoglycemia (glucose under 54 mg/dL) was 6% vs 2%. Mean resting heart rate rose by 1 to 4 beats per minute.

The placebo column matters

Sixteen percent of people on placebo reported nausea. Eleven percent reported constipation. They were on the same reduced-calorie diet with the same clinic visits. The honest measure of the drug's contribution is the difference: 28 points for nausea, 13 for constipation, 18 for vomiting. The tool reports that difference and its reciprocal, the number of people treated for one extra case, so you can compare reactions on the same footing.

Ozempic at 0.5 and 1 mg

The Ozempic label's Table 1 comes from two placebo-controlled type 2 diabetes trials with 32.9 weeks mean exposure: nausea 15.8% (0.5 mg) and 20.3% (1 mg) versus 6.1%; vomiting 5% and 9.2% versus 2.3%; diarrhea 8.5% and 8.8% versus 1.9%. Any gastrointestinal reaction: 32.7% and 36.4% versus 15.3%. Discontinuation for gastrointestinal reactions was 3.1%, 3.8% and 0.4%. In the trial comparing 2 mg with 1 mg, gastrointestinal reactions were 34% versus 30.8%. Lower rates than Wegovy partly reflect lower doses and partly a different population.

7.2 mg

The Wegovy label's STEP UP table reports nausea 39% (7.2 mg) versus 35% (2.4 mg) versus 13% (placebo), vomiting 22% versus 16% versus 6%, and constipation 20% versus 19% versus 8%. Five percent of 7.2 mg patients stopped for adverse reactions. The STEP UP publication adds dysesthesia at 22.9% on 7.2 mg against 6.0% on 2.4 mg (PubMed 40961952). The dose comparison covers the efficacy side.

When

Neither label publishes week-by-week rates. Both say the same thing in words: gastrointestinal reactions were most frequently reported during dose escalation. The pooled STEP 1 to 3 analysis (PubMed 34514682) adds detail: 99.5% of gastrointestinal events on semaglutide were non-serious, 98.1% were mild to moderate, they were transient, and they occurred most often during or shortly after dose escalation. 4.3% of semaglutide participants stopped for them.

That gives the shape of the timeline the tool draws: the four step-ups in weeks 1 to 16 are the high-risk windows, and each new step restarts the clock. Maintenance is quieter but not silent. In STEP 4, people who had already reached 2.4 mg and continued it for 48 more weeks still reported gastrointestinal events at 49.1%, versus 26.1% in those switched to placebo (PubMed 33755728).

What this does not cover

The serious but rare warnings in the labels: pancreatitis, gallbladder disease, acute kidney injury from dehydration, diabetic retinopathy complications in people with type 2 diabetes, and the boxed warning on thyroid C-cell tumors seen in rodents. Those are label sections 5.1 to 5.10 and a conversation with your prescriber. The FormBlends article on semaglutide side effects walks through them in more detail. And compounded semaglutide was in none of these trials; its rates are assumed from the brand data, not measured.