Your first 90 days on a GLP-1
Week by week: what the starter dose actually feels like, when appetite changes show up, when your provider will titrate, and the three weeks most people find hardest.
This is the most common question we get, and the honest answer is more nuanced than the headline trial numbers suggest.
The mechanism difference
Semaglutide activates the GLP-1 receptor. Tirzepatide activates GLP-1 and GIP — a second incretin receptor involved in insulin sensitivity and fat metabolism. Two pathways rather than one.
What the trials showed
| Semaglutide | Tirzepatide | |
|---|---|---|
| Trial | STEP-1 | SURMOUNT-1 |
| Duration | 68 weeks | 72 weeks |
| Average loss | ~15% body weight | ~20% body weight |
| Placebo arm | ~2.4% | ~3% |
| Dosing | Weekly injection or daily oral | Weekly injection |
Different trials, different populations — not a head-to-head — but the direction is consistent across the evidence base.
Why the stronger option is not automatically yours
- Tolerance. Some people handle one considerably better than the other. Side-effect burden decides adherence, and adherence decides results.
- Cost. Tirzepatide generally costs more. A medication you stay on for eighteen months beats a better one you drop at month four.
- Oral option. Only semaglutide comes in tablet form. For genuinely needle-averse patients that is decisive.
- Availability. Supply of both brand and compounded formulations shifts. Your provider works with what can actually be dispensed.
Most patients start on semaglutide and move to tirzepatide if response is inadequate. Starting on the strongest option is not always the fastest route to a result.
Switching between them
It is common and straightforward, but not a like-for-like dose swap. Your provider restarts titration at an appropriate level rather than matching milligram for milligram.
This is education, not a prescription. Doses, targets and schedules described here are illustrative. What is right for you depends on your history, your labs and your provider’s judgement.