Switching from semaglutide to tirzepatide dosage
You are trying to work out how much to draw or when to step up.
Reference and calculator, not medical advice. Dosing figures below are transcribed from FDA-approved prescribing information and link back to it. Last reviewed August 2026.
There is no conversion factor between these molecules. They are different drugs with different receptor targets and separately determined schedules — tirzepatide acts at both GIP and GLP-1 receptors, semaglutide at GLP-1 alone — so no ratio exists that turns a dose of one into an equivalent dose of the other. Charts that publish one are inventing it.
What the labels actually describe is that each product has its own starting dose, and neither makes an exception for someone arriving from the other. Both schedules are below so you can see they are not multiples of each other.
Side-by-side
Structural facts from each product’s prescribing information.
| Product | Active ingredient | Indication | Frequency | Start | Max labelled | Steps to max |
|---|---|---|---|---|---|---|
| Zepbound Eli Lilly | Tirzepatide | Weight management | Weekly | 2.5 mg | 15 mg | 6 |
| Wegovy Novo Nordisk | Semaglutide | Weight management | Weekly | 0.25 mg | 2.4 mg | 5 |
mg → syringe units converter
U-100 syringe. Formula: (dose ÷ concentration) × 100.
Check the concentration printed on the vial you are actually holding. The same dose in milligrams is a completely different mark on the syringe at a different concentration. If the number here does not match what your prescriber told you, trust your prescriber.
The Zepbound schedule has 6 steps and tops out at 15 mg, but the top step is a ceiling rather than a target — plenty of people maintain below it indefinitely. Which step is right for you is the one thing this table cannot tell you, and the one thing your prescriber can.
Common questions
- What is the starting dose of Zepbound?
- The prescribing information lists 2.5 mg once weekly as the starting dose, held for the first four weeks before any increase.
- What is the maximum labelled dose of Zepbound?
- 15 mg once weekly, reached through the stepped schedule shown above.
- How many units is 5 mg at 20 mg/mL?
- 25.0 units on a U-100 syringe. The arithmetic is (dose ÷ concentration) × 100, and it only holds if the concentration on your vial matches.
Sources and last review
Every dosing figure on this page is transcribed from an FDA-approved label and links back to it. Conversions are arithmetic you can repeat by hand. Nothing here is reviewed by a clinician, and this site does not employ one — which is exactly why what I do publish stays traceable to its source.
- Zepbound (Tirzepatide) prescribing information — Eli Lilly, label revised 6 May 2026, checked 7 August 2026
- Wegovy (Semaglutide) prescribing information — Novo Nordisk, label revised 30 June 2026, checked 7 August 2026
Transcribed from the labels above and checked by me — Gavin, who builds this site, takes a GLP-1, and is not a clinician. Last reviewed August 2026. Found an error? [email protected] — I treat corrections as bugs. How this site is built and funded.