Semaglutide is, today, the most searched-for peptide in the weight control world — and probably the most misunderstood when it comes to dosing. Let's clear up both: what it does and how to calculate it correctly.
In short: Semaglutide works on the GLP-1 receptor and is titrated over 4-week phases, from 0.25 mg up to a 2.4 mg maintenance dose, and the most common mistake isn't the drug itself but converting those milligrams into the wrong syringe units based on your vial's concentration.
What is it and how does it work?
Semaglutide is a GLP-1 receptor agonist (a hormone the gut naturally produces on its own). By acting on that receptor, it slows gastric emptying, reduces appetite, and improves insulin sensitivity. It's the same mechanism shared by other well-known GLP-1s, and the reason it's so closely tied to weight control.
Why the dose is raised gradually (titration)
Almost no one starts directly at the “final” dose. The reference protocol increases gradually every 4 weeks, precisely to reduce digestive side effects while the body adapts:
- Weeks 1-4: 0.25 mg weekly
- Weeks 5-8: 0.5 mg weekly
- Weeks 9-12: 1 mg weekly
- Weeks 13-16: 1.7 mg weekly
- Week 17 onward: 2.4 mg maintenance
This schedule is the usual reference, not a prescription. The dose, the pace of increase, and whether it's right for you should be decided by a healthcare professional.
The real problem: converting mg to syringe units
This is where most people go wrong: the dose is stated in milligrams, but the syringe is loaded in units. To convert between the two, you need your vial's concentration (which depends on the vial's mg and the water you added during reconstitution), and apply that concentration to the dose for the week you're on.
Getting it wrong in either direction has consequences: drawing too little means the dose “does nothing” (and the protocol gets abandoned thinking it doesn't work), and drawing too much breaks the gradual schedule that's specifically meant to minimize side effects.
Semaglutide vs. tirzepatide
Tirzepatide follows very similar logic (also titrated in phases), but it acts on two receptors instead of one (GIP and GLP-1), which in practice changes its dosing schedule: it starts at 2.5 mg weekly and rises to 15 mg maintenance — different numbers from semaglutide, so the two schedules can't be mixed.
How to avoid the calculation mistake
The simplest way to avoid getting it wrong is to stop doing the math from memory every week. Our semaglutide and tirzepatide calculator already has the full titration table built in: pick the phase you're on and it shows the exact units to draw, with the syringe drawn out.
