Tirzepatide
GLP-1 + GIP dual receptor agonist (Mounjaro, Zepbound)
Tirzepatide is a once-weekly injectable that activates both the GLP-1 and GIP receptors, lowering appetite and blood sugar. It is FDA-approved for type 2 diabetes (Mounjaro, 2022) and chronic weight management (Zepbound, 2023). In the SURMOUNT-1 trial, adults on 15 mg weekly lost an average of 20.9% of body weight over 72 weeks.
Quick reference
How Tirzepatide is dosed in practice
Per the FDA labels, you start at 2.5 mg once a week for 4 weeks, then increase to 5 mg weekly. That first dose is for getting used to the drug, not for weight loss or blood-sugar control.
Zepbound maintenance for weight loss is 5 mg, 10 mg or 15 mg weekly. For adult Mounjaro use, further increases are made only if additional glycemic control is needed, in 2.5 mg steps after at least 4 weeks on the current dose; 7.5 or 12.5 mg can be continued if effective. Reaching 15 mg takes at least 20 weeks (2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg). Many people stay at a lower dose if it works and is tolerated.
Inject once a week on the same day, at any time of day, with or without food. If side effects are hard to tolerate, prescribers often wait longer before the next increase.
Where the numbers come from: the FDA labels and the SURPASS and SURMOUNT phase 3 trials. 15 mg weekly is the labeled maximum.
Work out the units to draw with the reconstitution calculator and how long a vial lasts with the vial duration calculator.
How Tirzepatide works
Tirzepatide was the first approved drug to activate both the GLP-1 and GIP receptors. The GLP-1 part works like semaglutide: less appetite, slower stomach emptying, glucose-dependent insulin release. GIP is a second gut hormone involved in insulin release and fat metabolism; how much it adds on its own is still being studied.
In the head-to-head SURMOUNT-5 trial in adults with obesity, tirzepatide produced more weight loss than semaglutide (about 20% vs 14% of body weight at 72 weeks). In the SURPASS-2 trial in type 2 diabetes, it lowered HbA1c more than semaglutide 1 mg.
The half-life is about 5 days, which supports once-weekly dosing.
In the DoseCraft framework, tirzepatide addresses Insulin Resistance (blood-sugar control and insulin sensitivity), with knock-on effects on Inflammation and ATP Shortage through weight loss and better metabolic health.
Safety + side-effect profile
Side effects are similar to semaglutide and are mainly digestive, mostly during dose increases.
Boxed warning: tirzepatide caused thyroid C-cell tumors in rats; whether it does in humans is unknown. Don't use it with a personal or family history of medullary thyroid carcinoma (MTC) or with MEN 2. Other label warnings: pancreatitis, gallbladder problems, low blood sugar when combined with insulin or sulfonylureas, kidney problems from dehydration, and severe stomach and bowel problems. Not recommended in pregnancy.
Interactions: don't combine with semaglutide, liraglutide or retatrutide — overlapping action, untested combination. With insulin or sulfonylureas, those doses often need lowering. Oral birth control: tirzepatide can make it less effective; the label advises switching to a non-oral method, or adding a barrier method, for 4 weeks after starting and for 4 weeks after each dose increase.
Lean mass: part of the weight lost is lean tissue, not just fat. Resistance training and enough protein are the standard advice to limit this.
- • Nausea (the most common side effect, mainly during dose increases)
- • Diarrhea, constipation or vomiting
- • Reflux / heartburn (especially with large meals)
- • Fatigue in the first weeks
- • Less 'food noise' (intended effect)
- • Injection-site reactions
Frequently asked
What is Tirzepatide?
Tirzepatide is a once-weekly injectable that activates both GLP-1 and GIP receptors. It is FDA-approved for type 2 diabetes (Mounjaro, 2022) and chronic weight management (Zepbound, 2023). In a head-to-head trial in adults with obesity it produced more weight loss than semaglutide.
What's the standard Tirzepatide titration?
Per the FDA labels: 2.5 mg weekly for 4 weeks, then 5 mg weekly. Zepbound maintenance for weight loss is 5 mg, 10 mg or 15 mg weekly. For adult Mounjaro use, increase further only if additional glycemic control is needed, in 2.5 mg steps after at least 4 weeks on the current dose; 7.5 or 12.5 mg can be continued if effective. Going all the way to 15 mg takes at least 20 weeks: 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg. Many people stay at a lower dose if it works.
Tirzepatide vs Semaglutide — which is better?
In the head-to-head SURMOUNT-5 trial in adults with obesity, tirzepatide led to more weight loss than semaglutide (about 20% vs 14% of body weight at 72 weeks). In type 2 diabetes (SURPASS-2), it lowered HbA1c more than semaglutide 1 mg. Side effects are similar for both and mostly digestive. The better choice depends on your health, tolerance and coverage.
Can I stack Tirzepatide with Semaglutide or Retatrutide?
No. Semaglutide acts on the GLP-1 receptor too, and retatrutide adds GIP and glucagon receptor activity. Combining them hasn't been studied and would be expected to add side effects. If you switch from semaglutide, the labels don't define a washout — your prescriber sets the timing, and tirzepatide is started at 2.5 mg.
How much weight can I lose on Tirzepatide?
In SURMOUNT-1, adults without diabetes lost an average of 15.0% of body weight on 5 mg, 19.5% on 10 mg and 20.9% on 15 mg over 72 weeks, compared with 3.1% on placebo. Individual results vary widely.
What's the lean mass story with Tirzepatide?
As with other weight-loss drugs, part of the weight lost on tirzepatide is lean tissue. There's no good evidence that tirzepatide itself protects muscle. Resistance training and enough protein are the standard advice to limit muscle loss.
Are there long-term safety concerns with Tirzepatide?
Tirzepatide has been on the market since 2022, with phase 3 trials lasting up to about 3 years. Known risks include pancreatitis, gallbladder problems and the boxed warning about thyroid C-cell tumors in rats (avoid with a personal or family history of MTC or with MEN 2). Longer-term data are still accumulating.
What happens when I stop Tirzepatide?
Weight regain is common. In SURMOUNT-4, people switched to placebo after 36 weeks regained an average of 14% of body weight over the following year, while those who stayed on tirzepatide kept losing. Plan any stop with your prescriber; there's no tested tapering schedule.
Protocols using Tirzepatide
Outcome-driven stacks with phased dose schedules and cited PMIDs.
Head-to-head comparisons
Cited side-by-side breakdowns that include Tirzepatide.
Related compounds
Often researched, stacked, or compared with Tirzepatide.
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