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Comparison

Semaglutide vs Tirzepatide

Two weekly GLP-1 family shots people compare for weight loss and blood-sugar steadiness — different receptor coverage, different dosing ramp.

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Field
Semaglutide
Tirzepatide
Category
GLP-1
GLP-1
Common alias
GLP-1 agonist (Ozempic, Wegovy)
Dual GIP/GLP-1 (Mounjaro, Zepbound)
Example vial
5 mg + 2 mL BAC water
10 mg + 2 mL BAC water
Concentration
2.50 mg/mL
5.00 mg/mL
Example dose
0.25 mg
2.5 mg
Doses per week
1× / week
1× / week
Doses per vial (rounded down)
20
4
Approx vial duration
20.0 weeks
4.0 weeks

Semaglutide and Tirzepatide both show up in the same conversations, but they aren't interchangeable. The table above lays the vial math side by side so you can see how concentration, doses-per-vial, and weekly cadence actually compare. The sections below walk through what each one is, how each is studied, and how each shows up in a tracked log — in plain English, no recommendations.

Tiebreakers

Where Semaglutide and Tirzepatide actually diverge

SemaglutideTirzepatide
Cadence1/wk1/wk
Concentration on example2.50 mg/mL5.00 mg/mL
Math weeks per vial20.04.0
CategoryGLP-1GLP-1

Bolded values are the higher of the two on numeric rows. Same-value rows aren't a verdict — they're shared properties.

Semaglutide vs Tirzepatide: the actual decision

The cleanest way to think about this matchup is receptor coverage. Semaglutide is a single-target GLP-1 agonist; tirzepatide is dual, hitting GLP-1 and GIP at the same time. The dual hit is the entire reason the published weight-loss numbers for tirzepatide land higher in head-to-head trials — SURMOUNT-1 reported about 22.5 percent average loss at 72 weeks against the roughly 15 percent semaglutide showed in STEP-1. The cadence in a tracker is identical (one shot a week), but the titration ladders are not interchangeable, and dose strings on the syringe are not the same numbers.

Tirzepatide's titration ladder climbs through 2.5, 5, 7.5, 10, 12.5, and 15 mg, with the early steps spent largely getting the gut tolerant rather than chasing weight loss. Semaglutide's path runs 0.25, 0.5, 1.0, 1.7, 2.4 mg with the same logic. A reader logging both in the same calendar will notice that tirzepatide's middle steps are where most of the loss shows up, while semaglutide tends to feel more linear week to week. Neither curve is a guarantee for any individual person, which is why a well-kept log matters more than the trial average.

Mechanism, cadence, and what shows up in a log

Side-effect profile reads similarly in the two molecules — nausea, transient constipation, and the appetite-suppression that drives most of the weight loss — but tirzepatide's GIP component changes the texture of the early weeks for some people, and the gut-tolerance window is the place a careful log earns its keep. Both molecules carry the same boxed warning around C-cell tumors in rodents, both are administered with the same kind of insulin syringe or pre-filled pen, and both reconstitute identically when sourced as lyophilized powder from a research supplier.

Practically, the question that brings most people to this page is which one to plan around for a six-month log. The answer is structural rather than chemical: tirzepatide tends to require fewer dose-tolerance retreats but a longer total ramp, while semaglutide's lower-dose plateau is shorter and easier to sit on if the goal is steady-state rather than maximum loss. The calculator pages linked below let you plug your own vial size and dose into the math; the table at the top of this page does the comparison at the example vials only.

Semaglutide vs Tirzepatide: the numbers, side by side

Start with what actually goes into a syringe. The example Semaglutide vial on this site reconstitutes 5 mg in 2 mL of bacteriostatic water — about 2.50 mg per mL, which yields roughly 20 doses at the 0.25 mg example and lasts about 20.0 weeks at 1 dose per week. The example Tirzepatide vial reconstitutes 10 mg in 2 mL (5.00 mg/mL), which yields about 4 doses at 2.5 mg and stretches roughly 4.0 weeks at 1 dose per week. Those numbers are the starting point most people forget to write down, and they decide everything downstream — refill timing, unit count on the syringe barrel, and whether a 30-mL bac-water bottle stretches across one vial or two.

Category context matters too. Both Semaglutide and Tirzepatide sit in the GLP-1 bucket, so the head-to-head questions readers bring here are usually about cadence, titration step size, and which of the two molecules logs more cleanly inside a longer protocol rather than a from-scratch category choice. Cadence helps frame the rest: Semaglutide is logged about 1× per week in the example schedule, Tirzepatide about 1×.

The single most-asked-about mistake on each page is worth surfacing here, because they rarely overlap. On the Semaglutide side: Switching to a new vial of the same peptide and reusing the old unit count without re-running the calculation against the new vial's diluent volume. On the Tirzepatide side: Reusing the unit count from a previous vial after switching to a new vial that was reconstituted with a different diluent volume. Both are the kind of thing a tracked log catches early and an untracked routine catches late.

Top Semaglutide question
How is semaglutide reconstituted?

By adding a measured volume of bacteriostatic water to the lyophilized vial through the rubber stopper, then swirling — not shaking — until the powder fully dissolves into a clear solution. The exact diluent volume is up to the user; common choices for a 5 mg vial are 1, 2, or 3 mL.

Top Tirzepatide question
How is tirzepatide reconstituted?

By drawing a measured volume of bacteriostatic water and injecting it slowly into the lyophilized vial through the rubber stopper, then swirling — not shaking — until the powder fully dissolves. Diluent volume choices typically range from 2 to 5 mL depending on vial strength and preferred per-dose unit count.

The calculator pages linked below let you swap your own vial size, diluent volume, and dose into the same math — these example numbers exist so the comparison renders with concrete figures instead of placeholders.

Frequently asked questions about Semaglutide vs Tirzepatide

How is semaglutide reconstituted?
By adding a measured volume of bacteriostatic water to the lyophilized vial through the rubber stopper, then swirling — not shaking — until the powder fully dissolves into a clear solution. The exact diluent volume is up to the user; common choices for a 5 mg vial are 1, 2, or 3 mL.
How many units of semaglutide are in 0.25 mg?
It depends on the concentration of your vial. On a 5 mg vial reconstituted with 2 mL of bacteriostatic water, 0.25 mg is exactly 10 units on a U-100 insulin syringe. On a 5 mg vial reconstituted with 1 mL, the same dose is 5 units.
Why is semaglutide dosed weekly?
Because its half-life is approximately one week, which keeps blood plasma levels stable on a once-weekly injection schedule. That cadence is part of why semaglutide became attractive relative to earlier GLP-1 peptides that required daily dosing.
How is tirzepatide reconstituted?
By drawing a measured volume of bacteriostatic water and injecting it slowly into the lyophilized vial through the rubber stopper, then swirling — not shaking — until the powder fully dissolves. Diluent volume choices typically range from 2 to 5 mL depending on vial strength and preferred per-dose unit count.
How many units of tirzepatide are in 2.5 mg?
It depends on the concentration. On a 10 mg vial reconstituted with 2 mL of bacteriostatic water (5 mg per mL), 2.5 mg is exactly 50 units on a U-100 syringe. With 4 mL of diluent (2.5 mg per mL), the same dose is 100 units.
Why is tirzepatide dosed weekly?
Because its half-life is roughly five days, which keeps plasma levels stable on a once-weekly schedule. That long half-life is also why a single missed dose has less effect than missing a dose of a daily peptide.

Related on Peptide Pilot

Log Semaglutide and Tirzepatide side by side in the app

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