Semaglutide Weight Loss Calculator
Quick answer: In the STEP-1 trial, adults on weekly 2.4 mg semaglutide lost an average of 14.9% of body weight over 68 weeks — for a 220 lb person, roughly 33 lb. Loss typically shows from month one, accelerates after reaching full dose around month 4-5, and plateaus near month 14-16. Enter your weight below for your personal projection.
Projection uses STEP-1 trial averages — population averages with full titration and lifestyle support. Individual results vary widely; roughly 1 in 7 participants were non-responders.
Semaglutide dose schedule
| Phase | Dose | Notes |
|---|---|---|
| Weeks 1–4 | 0.25 mg weekly | Starter dose — tolerance building, minimal weight effect expected |
| Weeks 5–8 | 0.5 mg weekly | First clinically active dose for many |
| Weeks 9–12 | 1.0 mg weekly | Appetite suppression usually obvious by now |
| Weeks 13–16 | 1.7 mg weekly | Second-to-last step |
| Week 17+ | 2.4 mg weekly | Full maintenance dose used in STEP trials |
What the trials actually showed
Semaglutide's weight-loss evidence is unusually deep. STEP-1 (2021, New England Journal of Medicine) put 1,961 adults without diabetes on weekly 2.4 mg or placebo: the semaglutide group averaged 14.9% body-weight loss at 68 weeks versus 2.4% on placebo, and more than half lost over 15%. STEP-5 extended the picture to two years, showing losses were maintained at around 15% with continued treatment.
Beyond the scale, the SELECT trial (17,604 participants) showed a 20% reduction in major cardiovascular events in people with existing heart disease — the result that pushed insurers and regulators to treat semaglutide as more than a vanity drug.
One number worth respecting from every trial: roughly 1 in 7 participants lost less than 5% — genuine non-responders exist, and no calculator can predict which side of that line you're on.
Month-by-month: what a typical curve looks like
Months 1–2 are titration months at low doses; average trial loss here is modest (2-4%) and some people see nothing yet — this is the phase where most people wrongly conclude it 'isn't working.' Months 3–6 are the steep part of the curve once doses reach 1.0-2.4 mg: appetite suppression is strongest and most of the headline loss accumulates here and through month 9.
From roughly month 12-14 the curve flattens toward a plateau. That's not failure — it's the new energy equilibrium at a lower weight. In STEP-5, weight held stable from about week 60 through week 104 with continued dosing.
The muscle problem nobody should skip
Body-composition substudies suggest a meaningful share of semaglutide weight loss — figures around 25-40% in some analyses — can come from lean mass if nothing is done about it. The countermeasures are boring and effective: protein around 1.8-2.4 g per kg of body weight (our protein calculator gives your number), resistance training at least twice a week, and avoiding stacking an aggressive manual calorie cut on top of the drug's appetite effect.
Side effects and how people manage them
Nausea is the signature effect (about 44% in STEP-1), concentrated around dose increases, alongside constipation, diarrhea and reflux. Practical management from clinical guidance: smaller meals, less fat at the meal after injection, hydration, and not rushing titration — staying an extra 4 weeks on a tolerable dose costs little in a 68-week journey.
The serious-but-rare list includes pancreatitis and gallbladder disease (gallstones become more likely with any rapid weight loss), and the label carries a thyroid C-cell tumor warning from rodent studies — a contraindication for anyone with personal or family history of medullary thyroid carcinoma or MEN2.
What happens if you stop
The STEP-1 extension answered this bluntly: a year after stopping semaglutide and support, participants had regained about two-thirds of what they lost. Current obesity-medicine consensus treats semaglutide like blood-pressure medication — a long-term therapy for a chronic condition — with the habits built during treatment determining how much survives any eventual off-ramp.
Compounded and gray-market semaglutide
Because brand supply and price pushed many toward compounded or 'research' semaglutide vials, the reconstitution math became a real safety topic: unlike pens, vials require you to compute your own dose. If that's your situation, our semaglutide reconstitution calculator does the units math, and the practical rule is absolute — recompute concentration for every new vial, because vial sizes vary (2, 5, 10 mg) while your dose shouldn't.
FAQ
How much weight can I lose on semaglutide in 3 months?+
Trial averages sit around 5-6% of body weight by month 3 — for a 220 lb person, roughly 11-13 lb. The early months are titration months, so the pace picks up after reaching higher doses, not before.
Why am I not losing weight on semaglutide?+
The usual reasons, in order: still on titration doses (under 1 mg), liquid calories and grazing that bypass satiety signals, or being among the roughly 1-in-7 who respond weakly. If 12+ weeks at 2.4 mg produces under 5% loss, trials would class you as a non-responder — tirzepatide is the evidence-backed next conversation with a prescriber.
Ozempic vs Wegovy — is the weight loss different?+
Same molecule, different labels and maximum doses: Wegovy is approved for weight management up to 2.4 mg weekly; Ozempic is the diabetes label topping at 2 mg. The STEP weight-loss numbers were produced at Wegovy's 2.4 mg dose.
When does semaglutide weight loss plateau?+
Trial curves flatten around weeks 60-68. A plateau at month 4-5 is usually a dose or adherence issue rather than the real ceiling.
Educational content based on published clinical trial data. Projections are population averages, not personal predictions, and nothing here is medical advice — treatment decisions belong with a licensed prescriber.