Tirzepatide
The strongest approved weight shot: about a fifth of body weight in trials. One shot a week, start very low, and keep eating protein.
What it is
Tirzepatide is the once-a-week shot that quiets hunger and the constant thinking about food, and it is the most effective weight medicine you can actually get: around 20% of body weight at the top dose over a year and a half in trials. It is an approved prescription medicine with two large trial programs behind it, which puts it in a different league from almost everything else on this site.
The people this is for have real weight to lose, 30 pounds or more, and have found that willpower does not survive hunger. People with type 2 diabetes, prediabetes, or sleep apnea tied to weight get the most medical benefit. It is also the drug people reach for when semaglutide stalled them or made them too sick, since the second pathway tends to make it smoother at the same effect. It is the wrong tool for the last ten pounds, for anyone with an eating disorder history, and for anyone who is not willing to lift weights and eat protein, because a chunk of what you lose otherwise is muscle.
Week one, even at 2.5 mg, most people notice the food noise go quiet: you forget to eat, you leave food on the plate, a drink hits harder. Nausea tends to show up for two or three days after each dose increase and fades. Weight comes off at one to two pounds a week through the first months, faster for bigger people, and keeps going for a year or more if you keep stepping up. On the label's four-week steps the earliest you reach 7.5 mg is month three, and you only step up when the current dose stops working; plenty of people stay at 5 mg. Good looks like steady loss with your strength holding. It will not work if you stop; the trials show most of the weight returns within a year of quitting.
Start at 2.5 mg subQ (just under the skin with an insulin needle) once a week, same day each week, any time, with or without food. Hold four weeks, then step to 5 mg, then 7.5, then 10, each for at least four weeks, and only step up when the current dose has stopped working; 15 mg is the ceiling and plenty of people never need it. Belly, thigh, or back of the arm, rotating. The mistakes: stepping up on schedule when 5 mg is already doing the job, skimping on protein and losing muscle, not drinking enough, and letting constipation build for two weeks before dealing with it. Keep 100 grams of protein a day as a floor and lift twice a week. A 20 mg vial is eight weeks at 2.5 mg, four at 5 mg, and under two at 15 mg, so the budget climbs as the dose does.
The evidence is as good as it gets here. In SURMOUNT-1, adults without diabetes lost about 15% at 5 mg and about 21% at 15 mg over 72 weeks, against about 3% on placebo. In a head-to-head trial against semaglutide, tirzepatide won clearly. The SURPASS program in type 2 diabetes showed HbA1c drops of around two points and more weight loss than any comparator, and it is approved for sleep apnea in obesity as well. Approved as Mounjaro (diabetes, 2022) and Zepbound (weight, 2023). The same trials show the catch: stop the drug and the weight comes back.
If you want the best result and can get it, this is the one; semaglutide is the fallback with a decade more safety history, and retatrutide is the next step for people in trials or sourcing research product, with less appetite suppression and a metabolic push. Skip tirzepatide with a personal or family history of medullary thyroid cancer or MEN 2, and get a plan from your prescriber first if you have had pancreatitis, gallbladder disease, or diabetic eye disease.
What people use it for
Weight loss
Most evidenceSURMOUNT-1 randomized over 2,500 adults with obesity and found about 15% weight loss at 5 mg and about 21% at 15 mg over 72 weeks, versus about 3% on placebo, with most people at the top dose losing a fifth of their body weight. A later head-to-head trial showed it beats semaglutide. This is the strongest weight result for any approved medicine.
Blood sugar and diabetes
Most evidenceThe SURPASS trials in type 2 diabetes showed HbA1c reductions of around two points, more than semaglutide and insulin comparators, alongside more weight loss. Approved as Mounjaro in 2022 on that program. For someone with diabetes it is both the sugar drug and the weight drug.
What happens when you stop
Most evidenceSURMOUNT-4 took people who had lost weight on tirzepatide and switched half to placebo: those who stopped regained most of the weight within a year, those who continued kept losing. It holds appetite down while you take it and does not reset anything. Plan to stay on it, taper slowly, and build the habits that hold the line.
How it works
Where Tirzepatide sits in the class
Targets
Two incretin pathways in one molecule.
- Head-to-head trials show strong weight and blood-sugar results
- FDA approved (Mounjaro, Zepbound)
- Adds the GIP pathway on top of GLP-1
- Digestive side effects are common, especially while increasing the dose
How people use it
Safety, in brief
Things people sometimes notice
- Nausea for two or three days after each step up, worse with large or greasy meals
- Constipation that builds over weeks if you do not stay ahead of it with fluids and fiber
- Burping, reflux, and feeling full after a few bites
- Tiredness and feeling cold in the first weeks of fast loss
The full picture — stop signs and who should talk to a doctor first — is on the dosing guide.
Sources
The labels and studies behind this page. Each link opens the original on PubMed, DailyMed or ClinicalTrials.gov.
- Zepbound (tirzepatide) prescribing information
- Tirzepatide Once Weekly for the Treatment of Obesity
- Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes
- Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial