Every GLP-1 label begins at a dose well below the one that produced the published results. Wegovy starts at 0.25 mg once weekly for the first four weeks, a tenth of its 2.4 mg maintenance dose, and tirzepatide starts at 2.5 mg against maintenance doses of 5, 10 or 15 mg.
That gap is the single most useful thing to understand about month one. The trials behind the headline percentages, STEP 1 at 2.4 mg and SURMOUNT-1 at 5 to 15 mg, never measured a starting dose as a treatment in its own right. Here is what the labels schedule, what the earliest published data points actually show, and which first-month experiences the evidence says are normal.
- Wegovy runs 0.25 mg for weeks 1 to 4, then 0.5, 1 and 1.7 mg at four-week intervals before 2.4 mg from week 17.
- Tirzepatide starts at 2.5 mg and steps up in 2.5 mg increments, also every four weeks.
- No published trial reports a week-four average weight loss, because escalation is a period the trials passed through rather than an endpoint.
- The nearest early figures are 5.9% at three months in a real-world cohort and 10.6% at week 20 in the STEP 4 run-in.
- SURMOUNT-1 recorded gastrointestinal events occurring primarily during dose escalation, which is why the first month is mostly a tolerability test.
The starting dose is a tolerance dose
Every one of these labels opens below the dose the trials measured, and says so in the same words: the escalation exists to reduce the risk of gastrointestinal adverse reactions. It is not a trial of a low dose. It is a ramp.
| Product | Starting dose | Weeks at it | Usual maintenance dose | Starting dose as a share of maintenance |
|---|---|---|---|---|
| Wegovy (semaglutide) | 0.25 mg weekly | 1 to 4 | 2.4 mg weekly | 10% |
| Ozempic (semaglutide) | 0.25 mg weekly | 1 to 4 | 1 mg or 2 mg weekly | 13% to 25% |
| Zepbound and Mounjaro (tirzepatide) | 2.5 mg weekly | 1 to 4 | 5, 10 or 15 mg weekly | 17% to 50% |
| Wegovy tablets (oral semaglutide) | 1.5 mg daily | First 30 days | 25 mg daily | 6% |
Wegovy's injection schedule then runs 0.5 mg for weeks 5 to 8, 1 mg for weeks 9 to 12 and 1.7 mg for weeks 13 to 16, reaching 2.4 mg from week 17. Tirzepatide moves in 2.5 mg steps, also at four-week intervals. Both labels add the same caveat: if a dose is not tolerated during escalation, the prescriber may consider delaying the next step by four weeks. The full schedules for each brand are laid out in our semaglutide dosage chart and tirzepatide dosage chart.
No trial ever measured a starting dose as a treatment
This is the part that reframes the first month. STEP 1 randomised 1961 adults with overweight or obesity and no diabetes to semaglutide 2.4 mg or placebo for 68 weeks, and its headline 14.9% belongs to 2.4 mg (PMID 33567185). SURMOUNT-1 randomised 2539 adults without diabetes to tirzepatide 5 mg, 10 mg or 15 mg for 72 weeks, including a 20-week escalation period, and reported -15.0%, -19.5% and -20.9% (PMID 35658024).
Nobody was randomised to stay at 0.25 mg or 2.5 mg. Those doses appear in the trials only as the first rung of a ladder every participant was climbing. A first month on a starting dose is therefore not a small version of the trial result. It is a period the trials passed through on the way to the dose they were testing.
What the nearest published numbers show at one, three and five months
Published trials report their endpoint rather than a monthly curve, so an honest early picture has to be assembled from the few sources that measured earlier, each labelled with what it is.
| Point in treatment | Average weight loss | What it comes from |
|---|---|---|
| 4 weeks | No published trial average | Escalation period, not an endpoint in STEP 1 or SURMOUNT-1 |
| 3 months | 5.9% | Retrospective cohort of 175 patients on semaglutide for weight loss, mixed doses (PMID 36121652) |
| Week 20, about 4.5 months | 10.6% | STEP 4 run-in: 803 adults without diabetes who completed escalation and four weeks at 2.4 mg (PMID 33755728) |
| 6 months | 10.9% | Same retrospective cohort (PMID 36121652) |
| Week 68 | 14.9% | STEP 1, semaglutide 2.4 mg, no diabetes (PMID 33567185) |
Two things stand out. Both of the early figures come from people who were still escalating or had only just arrived at a maintenance dose, which is the honest description of the first four months. And the real-world cohort split sharply by diabetes status: 6.3% at three months for people without type 2 diabetes against 3.9% for people with it.
What none of these sources provides is a week-four average, because no published trial reports one. Any article offering a precise "expect this much in month one" figure is extrapolating.
Side effects cluster in exactly this window
SURMOUNT-1's authors put it plainly: the most common adverse events with tirzepatide were gastrointestinal, mostly mild to moderate, "occurring primarily during dose escalation". Adverse events caused discontinuation in 4.3%, 7.1% and 6.2% of the 5 mg, 10 mg and 15 mg groups against 2.6% on placebo (PMID 35658024).
On the semaglutide side, the Wegovy label's pooled adverse reaction table records nausea in 35% of adults on 2.4 mg against 13% on placebo, vomiting in 16% against 6% and constipation in 19% against 8%.
The pattern that matters for a first month is the timing rather than the totals. Symptoms concentrate around each dose increase and tend to settle before the next one, which means the first month and each of the three or four step-ups after it are the periods where tolerability is tested. We cover duration and management of each symptom in more detail in the piece on semaglutide side effects.
Four first-month observations that are not signs of failure
- The scale moving slowly. The dose in weeks 1 to 4 is a tenth of the Wegovy maintenance dose. Expecting a maintenance-dose result from it is expecting the ladder to work from its first rung.
- Appetite changing before weight does. The measured mechanism is reduced food intake, and intake changes before a four-week weight average can show it. We go through what the mechanism trials recorded in how semaglutide works.
- Week-to-week noise. Day-to-day body weight swings by one to two kilograms on fluid alone, which is larger than a week of expected loss at a starting dose.
- Effects that vary across the week. Semaglutide reaches its maximum blood concentration one to three days after an injection and has an elimination half-life of about one week, so the concentration curve is not flat within a dosing interval.
What the first month is actually for
Read against the labels, the first four weeks have one job: establishing whether the drug is tolerated well enough to keep climbing. Weight loss in that window is a side effect of the ramp, not the measurement.
That reframing also sets up the one genuinely useful thing to do with a starting weight, which is to record it properly. Every trial figure quoted above is a percentage of baseline weight, so a documented starting number is what makes any later comparison to STEP 1 or SURMOUNT-1 meaningful at all.
Decisions about whether to escalate, hold or stop belong to the prescriber. The labels are explicit that escalation steps are their call, including the option of delaying a step by four weeks where a dose is not tolerated.
Record the number month one is measured against
Put a starting weight against the published trial curves and see what each percentage is worth in pounds.
Running your own starting weight through the GLP-1 weight loss calculator turns STEP 1's 14.9% and SURMOUNT-1's 20.9% into pound figures and a week-by-week shape, which makes the flat stretch at the bottom of the ramp easier to read for what it is.
FAQ
What is the starting dose of semaglutide?
For Wegovy and Ozempic injections the label starting dose is 0.25 mg once weekly for the first four weeks, before escalation begins. Wegovy tablets start at 1.5 mg once daily for 30 days against a 25 mg maintenance dose. The starting dose exists to reduce gastrointestinal adverse reactions rather than to deliver the trial result.
What is the starting dose of tirzepatide?
Zepbound and Mounjaro both start at 2.5 mg once weekly for four weeks, then move in 2.5 mg steps at four-week intervals. SURMOUNT-1 measured outcomes at 5 mg, 10 mg and 15 mg after a 20-week escalation period, so 2.5 mg was a rung rather than a treatment arm.
How much weight should you lose in the first month on a GLP-1?
No published trial reports a week-four average, so there is no trustworthy figure to quote. The nearest data points are a real-world cohort averaging 5.9% at three months on semaglutide and the STEP 4 run-in averaging 10.6% at week 20, both covering people who were still escalating or had only just reached a maintenance dose.
Why does the dose go up every four weeks?
The labels tie the four-week interval to reducing the risk of gastrointestinal adverse reactions. SURMOUNT-1 found its gastrointestinal events occurred primarily during dose escalation, and both labels allow a prescriber to delay a step by four weeks if a dose is not tolerated.
Is it normal to feel no appetite change in week one?
Semaglutide reaches maximum blood concentration one to three days after an injection and has an elimination half-life of about a week, so concentrations build over the first several doses rather than peaking immediately. The starting dose is also a tenth of the Wegovy maintenance dose.
Do side effects mean the dose is too high?
That judgement belongs to the prescriber. What the trials show is that gastrointestinal symptoms cluster around dose increases and are usually mild to moderate, and that discontinuation for adverse events ran at 4.3% to 7.1% across the tirzepatide arms of SURMOUNT-1 against 2.6% on placebo.
Sources
- Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002. PMID: 33567185
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205-216. PMID: 35658024
- Rubino D, Abrahamsson N, Davies M, et al. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA. 2021;325(14):1414-1425. PMID: 33755728
- Ghusn W, De la Rosa A, Sacoto D, et al. Weight Loss Outcomes Associated With Semaglutide Treatment for Patients With Overweight or Obesity. JAMA Netw Open. 2022;5(9):e2231982. PMID: 36121652
- Wegovy (semaglutide) injection and tablets, US prescribing information, Novo Nordisk, revised June 2026. Escalation schedule, adverse reaction tables and pharmacokinetics.
- Mounjaro and Zepbound (tirzepatide) injection, US prescribing information, Eli Lilly. Starting dose 2.5 mg once weekly with 2.5 mg increments at four-week intervals.
This article is for information only and is not medical advice. Dosing, suitability and any change to treatment are decisions for your prescriber.