The most-asked question in every GLP-1 community is a timeline question, and the honest answer has a shape: appetite responds in days, the scale responds in weeks, the headline results take a year, and the first month systematically underestimates the drug because you are not yet on the real dose. Here is the week-by-week, and the checkpoint where 'not working' becomes a real signal instead of impatience.
The timeline, week by week
| Phase | What the data and pharmacology say |
|---|---|
| Days 1 to 7 (first injection) | Appetite quieting and earlier fullness begin for most within the first week; steady-state blood levels take 4 to 5 weeks, so effects build |
| Weeks 2 to 4 | Food noise reduction consolidates; scale movement modest and mostly water and glycogen at first |
| Weeks 4 to 12 | Escalation steps raise the effect; trial curves show roughly 4 to 8% body-weight loss by week 12 at escalating doses |
| Months 3 to 12 | Maintenance doses drive the bulk of loss; semaglutide's trial mean reached about 15% at 68 weeks, tirzepatide about 21% at 72 |
| The plateau | Curves flatten around 12 to 17 months; that is the drug's full expression, not a failure |
Why the first month lies to you
Starting doses (0.25 mg semaglutide, 2.5 mg tirzepatide) are tolerability ramps, not therapeutic targets: the labels escalate precisely because the effect is dose-dependent. Judging the drug at week 3 on a starter dose is judging a marathon at the first water station. The half-lives (about 7 days for semaglutide, 5 for tirzepatide) also mean each dose level needs a month to reach its own steady state before it shows you what it can do.
When 'not working' is a real signal
- Checkpoint that matters: if, after reaching a mid-range maintenance dose and holding it for 8 to 12 weeks, weight loss is under about 5% from baseline, you are statistically in the weak-responder tail: real, and worth a medication conversation (switching molecules often works).
- Appetite unchanged after a month at escalated doses is worth verifying the product first, especially with compounded vials: dosing math errors and product quality explain more 'non-response' than biology does in the gray tier.
- Plateau after a year of good response is not non-response: it is the expected curve; the conversation there is maintenance, not escalation forever.
Frequently asked questions
How long does it take for semaglutide to suppress appetite?
Most people notice appetite quieting within the first week of the first injection, building over 4 to 5 weeks as blood levels reach steady state and doses escalate. Full appetite effect arrives with maintenance doses, months in.
How long does it take for tirzepatide to suppress appetite?
Same shape as semaglutide, often reported slightly stronger once escalated: first effects within days to a week, consolidation over the first month, full effect at maintenance doses. The 2.5 mg start is a ramp, not the drug's real strength.
How much weight should I have lost after 3 months?
Trial curves put roughly 4 to 8% of body weight at week 12 under escalation, with wide individual spread. Under about 5% after 12 weeks at a real maintenance dose is the evidence-based flag worth discussing with a prescriber.