Guide
Tirzepatide, explained plainly
What it is, what it does to appetite, what the trials showed, and what the first three months tend to feel like.
Updated 2026-09-18 · Prices verified independently
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Tirzepatide is a once-weekly injection that changes how hungry you feel. That is the whole idea, and everything else follows from it.
A single weekly injection that activates two gut hormone receptors, GIP and GLP-1, rather than one. Most weight-loss injections act on one of those receptors. This one acts on both, which is the leading explanation for why it outperformed semaglutide when the two were tested head to head.
What the trials found
In SURMOUNT-1, adults with obesity lost an average of 19.5% of body weight on 10 mg and 20.9% on 15 mg over 72 weeks.
SURMOUNT-5 compared the two drugs directly. Participants on tirzepatide lost an average of 50.3 lb (22.8 kg); those on semaglutide lost 33.1 lb (15.0 kg).
Those are averages from controlled trials with structured support. Real-world results are more varied, and people who stop taking it generally regain a substantial share of the weight.
The dose ladder
Treatment starts low and steps up: 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg. The increases happen roughly every four weeks, and the point of going slowly is to keep the side effects manageable.
Why this matters for your budget
Many programmes charge more for higher doses, so the cost rises exactly as you reach the doses that work. Flat-rate programmes hold the price across the range — see what you actually pay.
What the first months feel like
Nausea, diarrhoea, constipation and reflux, concentrated in the weeks after each dose increase.
- Nausea is the common one, usually in the days after an increase.
- Constipation is widespread and is generally manageable with fluid and fibre.
- Appetite reduction can be abrupt, and eating too little protein is a real risk.
- Serious reactions are uncommon but exist, which is why prescribing should involve a clinician who takes a proper history.
What it costs
Through LillyDirect self-pay, single-dose Zepbound vials at 5 mg, 7.5 mg and 10 mg have been listed at $499/month, with lower starting doses nearer $299-$349. Compounded versions run from about $199 a month all in. The full table is in best tirzepatide providers.
If you are weighing it against the alternative, we compare them in tirzepatide vs semaglutide.
Read next
- Tirzepatide vs semaglutide
One trial put them head to head. The result was not close — but the cheaper drug still wins for some people.
- The best tirzepatide providers in 2026
21 programmes compared on what you actually pay in month two — not the teaser rate. Coreage Rx comes first.
- Semaglutide, explained plainly
The drug behind Ozempic and Wegovy: how it works, what it costs, and how it compares to the newer option.
- Is compounded GLP-1 medication still legal?
Short answer: yes, but in a much narrower form than in 2024 — and the FDA moved again this year.
- Coreage Rx tirzepatide review
Best overall on true monthly cost. We checked the advertised price against what you are actually billed. True cost: $199 a month.