The published timeline, point by point
Neither STEP 1 nor SURMOUNT-1 publishes a week-by-week table — they publish a curve — so the specific monthly averages circulating online are not from the papers. These are the points that genuinely exist in the literature.
Both drugs start below the therapeutic dose — semaglutide at 0.25 mg, tirzepatide at 2.5 mg — specifically to let the gut adjust. This month is about tolerating the drug, not losing weight, and expecting a dramatic change here is the most common reason people conclude it "is not working."
In a SURMOUNT-1 analysis, 82% of participants had reached at least 5% weight loss by week 12. The other 18% had not — and that is the number worth knowing, because it is not a verdict.
The 20-week run-in of STEP 4 took participants to −10.6% by the end of titration. Among the slower responders from week 12, 70% had crossed 5% by week 24.
The 36-week lead-in of SURMOUNT-4, at 10–15 mg, reached −20.9% — roughly eight months in.
STEP 1 plateaus around week 60 at −14.9%; SURMOUNT-1 reaches −20.9% by week 72. STEP 5 followed people to week 104 and found −15.2%, essentially unchanged — so after roughly 15 months the line is flat.
Why month one looks like nothing
Semaglutide starts at 0.25 mg and steps up roughly every four weeks. That opening dose is not a low treatment dose — it is a tolerance dose, chosen because starting at the full amount causes far more nausea and vomiting. You are not on a weight-loss dose in month one, so judging the drug on month one is judging something it was never asked to do.
What people do commonly notice in the first weeks is reduced appetite and getting full faster. That is the mechanism arriving before the scale reflects it.
What week 12 predicts — and what it does not
Week 12 is the first genuinely informative checkpoint. In a SURMOUNT-1 analysis, 82% of participants had reached at least 5% weight loss by then. The 18% who had not were more likely to be male, heavier at baseline and starting from a higher BMI.
Their outcome is the part worth knowing: 70% of them crossed 5% by week 24 and 90% by week 72, taking about 25 weeks on average instead of 12. They did finish lower than the fast responders — roughly 14.6% versus 23.3% at week 72 — so early response does carry information. But most people who start slowly still get to a clinically meaningful result, and quitting at week 12 forecloses that.
One caveat specific to Ozempic
Ozempic is approved for type 2 diabetes, not weight loss, and its trials measured weight only as a secondary endpoint. Most of the striking month-by-month results people share under the Ozempic name are either off-label use in people without diabetes, Wegovy results relabelled, or compounded semaglutide. The full picture is on our Ozempic before and after page, and the cross-drug comparison is in GLP-1 weight-loss results.