01 How it works
Tirzepatide activates both the GLP-1 receptor (fullness, slower digestion, insulin release) and the GIP receptor, a second gut-hormone pathway that appears to add to the effect on appetite and fat metabolism. Like semaglutide, it lasts about a week in the body.
02 Common uses
03 Run profile
Start at 0.5mg once a week, on the same day each week, and step up in small 0.5mg amounts only if you need to. Stay at least two weeks on each dose, and longer if you have side effects. Step up only if weight loss has slowed to less than about 1–2 lb a week. Once you are losing steadily, stay at that dose: there is no need to keep climbing. Many people find their dose well below the top of the ladder.
The profile shows the shape. Ask for the numbers for your vial, your goal and your timeline.
04 Pairs well with
05 What to watch for
Stomach effects — nausea, diarrhoea, constipation, cramping — mostly in the week or two after a step up. Smaller meals, less fatty food around dose day, and good hydration help. Severe abdominal pain radiating to the back, persistent vomiting or gallbladder pain need medical attention. Not for anyone with a personal or family history of medullary thyroid cancer or MEN2.
06 Evidence & status
Approved (as Mounjaro®/Zepbound®)Very well studied. In the SURMOUNT-1 trial, average weight loss reached about 20% at the highest dose over 72 weeks.
FDA-approved as the brand medicines Mounjaro® (type 2 diabetes) and Zepbound® (weight management). This page covers the compound itself.
Sources
- ZEPBOUND- tirzepatide injection, solution (prescribing information)DailyMed, U.S. National Library of Medicine, 2026 · Prescribing information
- MOUNJARO- tirzepatide injection, solution (prescribing information)DailyMed, U.S. National Library of Medicine, 2026 · Prescribing information
- ZEPBOUND (tirzepatide) injection, for subcutaneous use - initial FDA-approved labelU.S. Food and Drug Administration (Drugs@FDA), 2023 · Prescribing information
- Tirzepatide Once Weekly for the Treatment of ObesityThe New England Journal of Medicine, 2022 · Clinical trial
- FDA confirms end of tirzepatide shortageHealio (reporting the FDA decision of 19 December 2024), 2024 · Regulator document
- The Prohibited ListWorld Anti-Doping Agency, 2026 · Regulator document
Status and sources last checked November 3, 2026. Something out of date? Tell us.
07 How long until it works
Weight loss on tirzepatide is steady rather than sudden. In SURMOUNT-1, the main 72-week trial, people on the highest dose had lost about 21% of their body weight by the end, with the curve still sloping down at week 72, and most of the loss came after the dose had been built up over the first 20 weeks.
Appetite changes are usually noticed within the first one to two weeks on a dose; the scale follows. Two things set the pace: how fast the dose is stepped up, and how much is lost per week once it is working. Averaged over the trial, the full dose came to roughly 0.3% of body weight a week. If nothing has changed after four weeks on a dose, that is the signal the run profile above describes for stepping up.
08 Tirzepatide vs semaglutide
Both are once-weekly injections that act on the GLP-1 receptor; tirzepatide also acts on GIP. In their main trials, average weight loss at the highest dose was about 15% for semaglutide (STEP 1, 68 weeks) and about 21% for tirzepatide (SURMOUNT-1, 72 weeks). Those are two different trials in different people, not a head-to-head, but the gap is consistent across the studies both have run.
Side-effect profiles are similar: nausea, diarrhoea, constipation and decreased appetite lead both labels, mostly around dose increases. Semaglutide has the longer track record and the broader set of approved uses, including heart-disease risk reduction; tirzepatide has the larger average effect. Both carry the same warning about a personal or family history of medullary thyroid cancer.
Sema, Tirz or Reta, side by side →09 Stacking
The common pairings on this site are with a recovery peptide (BPC-157) for people training through a weight-loss phase, and with MOTS-C where energy is the complaint. There are no trials of tirzepatide combined with any peptide; the evidence for each is separate.
The one combination the label does speak to is with insulin or sulfonylureas, which raises the risk of low blood sugar. Anyone on those needs their doctor’s input before starting.
10 Where it stands legally
Tirzepatide is FDA-approved as Mounjaro (type 2 diabetes) and Zepbound (weight management, and obstructive sleep apnoea in adults with obesity). Compounded tirzepatide was permitted while the brand was in shortage; the FDA declared that shortage over on 19 December 2024, and compounding under the shortage rules had to end by 18 February 2025 for pharmacies and 19 March 2025 for outsourcing facilities.
Tirzepatide is not among the six peptides in the October 2026 HHS enforcement-discretion policy, so that policy does not apply to it. In sport, GLP-1 medicines are not on WADA’s Prohibited List; from 2026 WADA monitors semaglutide and tirzepatide use without banning them.
11 FAQ
Is it stronger than semaglutide?
On average, yes — trials comparing the two found more weight loss with tirzepatide. Individual responses vary.
Pen or vial?
Both exist. The pen is pre-mixed and dial-dosed; the vial is mixed yourself and measured with a syringe.
When should I step up?
Only if weight loss has slowed to less than about 1–2 lb a week after at least two weeks on your current dose, and side effects are mild. If you are losing steadily, stay where you are. Step up 0.5mg at a time, never more.
Can I stay on a lower dose?
Yes. Many people find their effective dose well below the top of the ladder and stay there for the long term.
Does tirzepatide cause hair loss?
Hair thinning was reported by about 5% of people on Zepbound in trials versus 1% on placebo. It is thought to follow rapid weight loss rather than the medicine itself, and generally recovers as weight stabilises.
What happens if I miss a tirzepatide dose?
Take it within 4 days (96 hours) of the missed day; otherwise skip it and take the next one on the usual day. Keep at least 3 days between doses. Never double up.
How long can tirzepatide stay out of the fridge?
The pen can be kept at room temperature, up to 30°C (86°F), for up to 21 days. For a compounded vial, follow the pharmacy’s label.
Can I stop tirzepatide and restart later?
The label gives no restart instruction. After more than a couple of weeks off, tolerance to the stomach effects drops, so the cautious approach is to restart lower and build back up. That is clinical reasoning, not trial data.
Educational information only — not medical advice. The Daily Stack does not sell or supply any products. Talk to a licensed healthcare professional about your own health decisions.