Research · 2 min read
Tirzepatide Side Effects: What the Label Actually Reports
The numbers people quote for tirzepatide usually arrive without the placebo column beside them. Here is the full table from the current label, with the control arm and the dose it belongs to.
Key takeaways
- Every rate in the label comes with a placebo column, and the placebo column is what makes it interpretable.
- Nausea peaks at 10 mg in the label's table rather than at the highest dose, so more drug does not simply mean more nausea.
- The label states most gastrointestinal effects happen during dose escalation and ease afterwards.
- Discontinuation for gastrointestinal reasons ran 1.9% to 4.3% by dose, against 0.5% on placebo.
- Hair loss is a labeled reaction, reported far more often in women, and described as associated with weight reduction.
- The semaglutide table is not comparable to this one: different trials, populations and dose arms, and no head-to-head.
The table, with its control
The current ZEPBOUND label reports adverse reactions from two weight-reduction trials, against a placebo group of 958 people and three dose groups: 5 mg (630), 10 mg (948) and 15 mg (941). Reading a rate without the placebo figure beside it is what turns a trial result into a scare number.
Nausea was reported by 8% on placebo, against 25% at 5 mg, 29% at 10 mg and 28% at 15 mg. Diarrhea 8% against 19, 21 and 23%. Vomiting 2% against 8, 11 and 13%. Constipation 5% against 17, 14 and 11%.
Notice what the dose columns do and do not do. Nausea does not climb steadily with dose — it is highest at 10 mg, not 15. Constipation runs the other way, highest at the lowest dose. A simple more-drug-more-side-effects story does not survive the table.
Most of it happens while the dose is going up
The label states plainly that the majority of nausea, vomiting and diarrhea events occurred during dose escalation and decreased over time. That is the single most useful sentence in the section, because it tells you when to expect the worst of it rather than only how likely it is.
The escalation is itself designed around this. The starting dose is 2.5 mg once weekly for four weeks, a dose the label says is for initiation and is not approved as a maintenance dose, and increases follow in 2.5 mg steps no sooner than every four weeks — explicitly, in the label's words, to reduce the risk of gastrointestinal adverse reactions.
Gastrointestinal reactions of some kind were reported by 56% at every dose against 30% on placebo. The number that matters more for a decision is how many people that made stop: 1.9% at 5 mg, 3.3% at 10 mg and 4.3% at 15 mg discontinued because of them, against 0.5% on placebo.
Hair loss is in the table too
Hair loss was reported by 1% on placebo against 5% at 5 mg, 4% at 10 mg and 5% at 15 mg. It is not a rumor and it is not hidden — it is a labeled adverse reaction with a placebo comparison.
The label adds two things worth carrying. It describes these reactions as associated with weight reduction, which is a different claim from being caused by the drug directly. And it reports the split by sex: 7.1% of women against 0.5% of men on ZEPBOUND, with 1.3% and 0% respectively on placebo.
No ZEPBOUND-treated patient discontinued because of hair loss in those trials; one placebo-treated patient did.
Why you cannot put this beside the semaglutide table
The companion page on this site reports semaglutide's numbers from its own label, and they look larger. They are not measuring the same thing.
The two sets come from different trials, with different populations, different durations, and different dose arms — a single 2.4 mg arm on one side, three dose arms on the other. Neither label reports a head-to-head comparison, and a percentage only means something against the control that ran beside it in the same trial.
If you want the comparison a reader actually wants, it is not in either label. What both labels do support is the same practical point: the gastrointestinal effects concentrate during escalation and ease after it.
Sources
- ZEPBOUND (tirzepatide) injection, for subcutaneous use — Highlights of Prescribing InformationTable 1, Adverse Reactions (≥2% and greater than placebo) in ZEPBOUND-treated adults with obesity or overweight, Studies 1 and 2: placebo N=958, ZEPBOUND 5 mg N=630, 10 mg N=948, 15 mg N=941; nausea 8 / 25 / 29 / 28%, diarrhea 8 / 19 / 21 / 23%, vomiting 2 / 8 / 11 / 13%, constipation 5 / 17 / 14 / 11%, hair loss 1 / 5 / 4 / 5%. Section 6.1: gastrointestinal adverse reactions in 56% at each dose against 30% on placebo; discontinuation for gastrointestinal reactions 1.9%, 3.3% and 4.3% against 0.5%; and the statement that the majority of nausea, vomiting and/or diarrhea events occurred during dose escalation and decreased over time. The Hair Loss paragraph: reactions associated with weight reduction, 7.1% female versus 0.5% male on ZEPBOUND and 1.3% versus 0% on placebo, with no ZEPBOUND-treated and one placebo-treated discontinuation. Sections 2.1 and 2.2: the 2.5 mg starting dose for four weeks, not approved as maintenance, 2.5 mg increments after at least four weeks, stated as being to reduce the risk of gastrointestinal adverse reactions.
Frequently asked questions
How common is nausea on tirzepatide?
The label reports 25% at 5 mg, 29% at 10 mg and 28% at 15 mg, against 8% on placebo, in two weight-reduction trials.
Does nausea get worse at higher doses?
Not straightforwardly. It is highest at 10 mg rather than 15 mg in the label's table, and constipation is highest at the lowest dose. The label reports rates by dose rather than a trend.
When are side effects most likely?
The label states the majority of nausea, vomiting and diarrhea occurred during dose escalation and decreased over time. The escalation schedule exists in part to reduce that risk.
How many people stopped because of side effects?
For gastrointestinal reactions: 1.9% at 5 mg, 3.3% at 10 mg and 4.3% at 15 mg, against 0.5% on placebo.
Is hair loss a real reported effect?
Yes. 5% at 5 mg, 4% at 10 mg and 5% at 15 mg against 1% on placebo, reported more often in women than men, and described in the label as associated with weight reduction.
Is tirzepatide better tolerated than semaglutide?
Neither label answers that. The two report different trials with different populations and dose arms, and no head-to-head comparison appears in either. Comparing the two tables directly is not a valid reading of them.