Semaglutide vs Tirzepatide
There is no winner on this page. What is set side by side is the published record behind each one, which is the part the two are rarely compared on.
Both in Metabolic and GLP-1
Both are approved, and for both the trial record is not the weak point. The difference is where the trouble moved. For semaglutide it moved into the vial: the one published test of grey market material found it dirty and over label rather than weak, so dosing carefully by that label meant overdosing. For tirzepatide the circulating practice is microdosing, which has been tested once, and at the smallest dose people lost under a kilogram in six months.
| Field | Semaglutide | Tirzepatide |
|---|---|---|
| What a trial gave | Large randomised placebo controlled trialsThe strongest evidence base of anything on this site | 5, 10 and 15 mg weeklySURMOUNT-1, about a fifth of body weight at the top dose |
| What circulates | Prescription doses, often from grey market vials | Microdoses below 2.5 mg weekly |
| The gap | Lands on a studied dose | Below the studied dose |
| How long it lasts | About seven days in people, which is why it is a weekly shot. The natural gut hormone it is copied from lasts about two minutes. | The entry gives no number for how long it lasts in the body. It says only that a fatty tail on the molecule stretches its stay far enough for one injection a week under the skin, which is how every human trial dosed it. |
| Route studied | Weekly injection of pharmaceutical product, in large trials. Also approved as a pill. | Under the skin, once a week, in large trials |
| Route used | Weekly injection at home, often mixed by the person from a powder vial. | Under the skin at home, once a week. Pharmacy mixed versions have also been sold as under the tongue liquids and dissolving tablets, neither an approved way to take it. |
| Vial sizes | 5, 10, 20, 30 mg | 5, 10, 15, 20, 40, 60 mg |
The distance, stated
Lands on a studied dose
Semaglutide
The risk moved off the molecule and into the vial. Three tested vials were far less pure than claimed and simultaneously over label, so careful dosing meant overdosing.
Below the studied dose
Tirzepatide
Microdosing was tested once. At the smallest dose people lost under a kilogram in six months.
What people get wrong
Semaglutide
People assume the huge trial results and the number on the label both apply to the vial that arrived in the mail. No trial has ever used research grade or compounded material, and the one published test of grey market vials found the street belief backwards: the product was not weak and underdosed, it was dirty and stronger than the label said, which is how somebody dosing by that label overdoses.
Tirzepatide
The mistake that costs money and safety is quoting the trial numbers while buying something the trials never used. The 20.9% figure comes from branded tirzepatide at the top weekly dose over 72 weeks, whereas the only randomised weight result anywhere near the tiny doses sold online was under a kilogram in six months, and roughly a quarter of people on that dose still had stomach and gut side effects.
Every figure above is carried across from each compound’s entry, which is where the citations live.
All 65 compounds on one page at what circulates vs what was studied, or pick another two to compare.