Semaglutide Results Week by Week: What the Trials Actually Show
There is no true week-by-week semaglutide chart from trials — results were reported at week 68 (−14.9%), week 104 (−15.2%) and week 208 (−10.2%). Here is what the data do show about the shape of the curve, side effects and plateaus.
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There is no real week-by-week semaglutide weight loss chart from the clinical trials. The major trials measured results at fixed endpoints — week 68 in STEP 1, week 104 in STEP 5, and week 208 in SELECT — not week by week [1][4][5]. At those checkpoints, average weight loss was −14.9% at 68 weeks in STEP 1 [1], −15.2% at 104 weeks in STEP 5 [4], and −10.2% at 208 weeks in SELECT, where weight loss continued over 65 weeks before flattening into a long plateau [5]. Outside of trials, a real-world cohort of 7,881 patients who started injectable semaglutide or tirzepatide averaged 8.7% weight loss at one year [2].
Those numbers are group averages, not personal predictions. Responses varied widely even among people following the same protocol under identical trial conditions [1].
Why there is no week-by-week chart from the trials
The trials were designed around a small number of fixed endpoints, not weekly weigh-ins. STEP 1’s co-primary endpoints were the percentage change in body weight and the achievement of at least 5% weight loss, both measured at week 68 [1]. STEP 5 measured its co-primary endpoints at week 104 [4]. SELECT, the cardiovascular outcomes trial, reported weight and waist measurements through week 208 [5].
Any chart that shows exact pounds or percentages lost in, say, week 3 or week 9 is not drawn from these trials. The published record supports statements about weeks 68, 104 and 208 — and about the overall shape of the curve — but not a week-by-week breakdown.
The other reason a weekly chart would mislead is individual variation. STEP 1 reported its week-68 results partly in responder bands rather than as a single curve, and those bands — shown in the week-68 results below — capture how differently people responded even under identical trial conditions [1].
What happens in the first 16 weeks
The first four months are mostly about getting to the full dose, not about maximum weight loss. In STEP 1, semaglutide started at 0.25 mg once weekly for the first 4 weeks, then the dose increased every 4 weeks until reaching the maintenance dose of 2.4 mg weekly by week 16 [1]. The 0.25 mg starting dose is a starter dose, not the full treatment dose.
The trial also allowed lower maintenance doses for participants who had unacceptable side effects at 2.4 mg — dose decisions were managed by the trial’s clinicians, not by participants [1]. Any question about dosing or titration pace belongs with a prescriber.
Everyone in STEP 1 also followed a lifestyle program: a 500-calorie-per-day deficit diet, 150 minutes of weekly activity such as walking, and counseling sessions every 4 weeks [1]. The trial population had a BMI of 30 or greater, or 27 or greater with at least one weight-related condition, and did not have diabetes (HbA1c below 6.5%) [1].
When nausea and other side effects hit, and how often people stop
Nausea and diarrhea were the most common adverse events with semaglutide in STEP 1. They were typically transient, mild-to-moderate in severity, and subsided with time [1]. The published results do not break down exactly when side effects began or eased week by week.
In STEP 1, 4.5% of the semaglutide group (59 participants) discontinued treatment because of gastrointestinal events, versus 0.8% of the placebo group (5 participants) [1]. In STEP 5, gastrointestinal adverse events were reported by 82.2% of the semaglutide group versus 53.9% of the placebo group, and most were mild-to-moderate [4].
SELECT told a similar tolerability story at scale: semaglutide was associated with fewer serious adverse events than placebo across every BMI category, with serious adverse event rates per 100 years of observation of 43.23, 43.54, 51.07 and 47.06 for semaglutide versus 50.48, 49.66, 52.73 and 60.85 for placebo [5]. However, discontinuation of the trial product was higher with semaglutide, and discontinuations rose as BMI class decreased [5].
The one-year benchmark: STEP 1 at week 68
STEP 1 enrolled 1,961 adults without diabetes, randomly assigned 2:1 to semaglutide 2.4 mg or placebo for 68 weeks [1].
At week 68, the mean weight change was −14.9% with semaglutide versus −2.4% with placebo, a treatment difference of −12.4 percentage points (95% CI −13.4 to −11.5) [1]. In absolute terms, that was −15.3 kg versus −2.6 kg, a difference of −12.7 kg [1].
| STEP 1 result at week 68 | Semaglutide | Placebo |
|---|---|---|
| Mean weight change | −14.9% | −2.4% |
| Mean absolute change | −15.3 kg | −2.6 kg |
| Lost ≥5% | 86.4% | 31.5% |
| Lost ≥10% | 69.1% | 12.0% |
| Lost ≥15% | 50.5% | 4.9% |
| Stopped due to GI events | 4.5% | 0.8% |
All figures from STEP 1 [1].
Note that the placebo arm still lost 2.4% on average with the lifestyle intervention alone — a reminder that the trial numbers include the effect of diet and activity counseling, not the drug by itself [1].
What one-year results look like outside of trials
Real-world results run lower than the trial curve. A retrospective study using electronic health record data from a large health system in Ohio and Florida identified 7,881 adults with overweight or obesity, without type 2 diabetes, who initiated injectable semaglutide or tirzepatide between 2021 and 2023 — 6,109 received semaglutide and 1,772 received tirzepatide [2]. The one-year figures below combine both medications.
Mean weight reduction at one year was 8.7% (standard deviation 9.6) across the whole cohort [2]. The results split sharply by whether people stayed on the medication. Discontinuation was defined as a gap of more than 90 days between exhausting the previous supply and the next dispense [2].
| Status at 1 year | Mean weight reduction |
|---|---|
| Early discontinuation (within 3 months) | 3.6% |
| Late discontinuation (3–12 months) | 6.8% |
| No discontinuation | 11.9% |
All figures from the retrospective cohort [2]; differences were significant at p < 0.001.
Among patients with prediabetes at baseline, HbA1c fell 0.1 points with early discontinuation, 0.2 with late discontinuation, and 0.4 with no discontinuation [2]. Notably, 80.8% of the cohort was on low maintenance dosages, and the authors attributed the gap versus phase 3 trials to higher discontinuation rates and lower maintenance doses [2].
Does weight loss keep going in year 2?
STEP 5 ran for 104 weeks and enrolled 304 adults (152 per arm) between October 5, 2018 and February 1, 2019 [4]. At week 104, mean weight change was −15.2% with semaglutide versus −2.6% with placebo, a difference of −12.6 percentage points (95% CI −15.3 to −9.8) [4].
STEP 1, a separate trial in a separate population, averaged −14.9% at week 68 [1]. The two trials were not designed to measure a year-2 increment, and neither reports one; what the endpoints do show is that the week-104 average sits close to the week-68 average, a picture closer to a plateau than a continued slide [1][4].
At week 104, 77.1% of the semaglutide group had lost at least 5% of baseline weight, versus 34.4% of the placebo group [4]. The trial’s baseline profile: mean age 47.3 years, mean weight 106.0 kg, mean BMI 38.5, and 77.6% female [4]. Completion was high — 92.8% attended the end-of-trial safety visit, and 79.9% were still on treatment at the end [4].
Years 2 to 4: how long does the plateau last?
SELECT followed 17,604 adults with preexisting cardiovascular disease and overweight or obesity, without diabetes [5]. In the semaglutide group, weight loss continued over 65 weeks and was then sustained for up to 4 years [5].
At week 208, semaglutide was associated with a mean weight reduction of −10.2% versus −1.5% with placebo (P < 0.0001), along with a waist circumference reduction of −7.7 cm versus −1.3 cm and a waist-to-height ratio change of −6.9% versus −1.0% [5]. Clinically meaningful weight loss occurred in both sexes and across races, body sizes and regions [5].
The SELECT average is lower than STEP 1’s −14.9%. The two numbers come from different trials with different populations — SELECT enrolled adults with preexisting cardiovascular disease [5], while STEP 1 enrolled adults with a BMI of 30 or greater, or 27 or greater with at least one weight-related condition, without diabetes [1]. Neither source states a single reason for the difference between the two averages.
SELECT’s main finding was not about weight at all: semaglutide was associated with a 20% reduction in major adverse cardiovascular events (hazard ratio 0.80, 95% CI 0.72–0.90) [5]. That is a population-level trial result, not a guarantee for any individual.
What the data show about stopping treatment
Two studies were specifically built to examine what happens around stopping. STEP 4 was designed to test continued weekly subcutaneous semaglutide versus placebo for weight-loss maintenance after an initial run-in period [3]. A published extension of STEP 1 studied weight regain and cardiometabolic effects after semaglutide withdrawal [6].
Separately, STEP 1’s design included a 7-week period off both the drug and the lifestyle intervention after week 68 [1].
The real-world cohort adds figures from routine care: people who discontinued within 3 months averaged 3.6% weight loss at one year, versus 11.9% for those who did not discontinue [2].
Where the new 7.2 mg dose fits
On March 19, 2026, the FDA approved Wegovy HD, a 7.2 mg semaglutide injection, for weight loss and long-term maintenance of weight loss in adults with obesity, or overweight with at least one weight-related condition [8]. It was the fourth approval under the Commissioner’s National Priority Voucher pilot program and was granted 54 days after filing [8].
The approval was supported by clinical data showing the higher dose produced additional average weight reduction compared with previously approved doses, with a safety profile consistent with known semaglutide side effects [8]. In people with both obesity and type 2 diabetes, the higher dose gave similar A1C lowering to the lower dose [8].
The safety picture matters here. The most common adverse reactions were gastrointestinal — nausea, vomiting, diarrhea, constipation and abdominal pain [8]. Reports of altered skin sensation (sensitivity, pain or burning) were common, occurred more frequently at the higher dose than at lower doses, and generally resolved on their own or with dose reduction; the FDA is investigating further [8]. Wegovy carries a boxed warning about the potential risk of thyroid C-cell tumors based on rodent findings, and it should not be used by people with a personal or family history of medullary thyroid carcinoma or with Multiple Endocrine Neoplasia syndrome type 2 [8].
A realistic month-by-month picture of the curve
Putting the trial data together, the shape of the curve looks like this:
- Month 1 (weeks 1–4): the 0.25 mg starter dose period — a titration step, not the full weight-loss dose [1].
- Months 2–4 (weeks 5–16): dose increases every 4 weeks, reaching the 2.4 mg maintenance dose around week 16 [1].
- Weeks 17–65 (roughly months 5–15): in SELECT, weight loss continued over 65 weeks before flattening [5].
- Week 68 (about 15.5 months): the STEP 1 average was −14.9% [1].
- Week 104 (2 years): the STEP 5 average was −15.2% — little added in year 2 [4][1].
- Years 2–4: flat. SELECT showed the loss sustained through week 208 [5].
| Checkpoint | Trial | Mean weight change |
|---|---|---|
| Week 68 (about 15.5 months) | STEP 1 | −14.9% [1] |
| Week 104 (2 years) | STEP 5 | −15.2% [4] |
| Week 208 (4 years) | SELECT | −10.2% [5] |
| 1 year, real-world cohort (semaglutide or tirzepatide) | EHR study | −8.7% [2] |
The SELECT average comes from a different trial population — adults with preexisting cardiovascular disease [5].
Individual variation and when to raise it with a clinician
The responder bands in the week-68 table show the spread directly: half of the semaglutide group in STEP 1 reached at least 15% weight loss, while roughly 13.6% did not reach even the 5% mark [1]. The trials allowed prescribers to lower maintenance doses for participants with unacceptable side effects [1].
Dose and titration decisions in the trials were made by clinicians, and the same applies outside them. Questions about a specific dose, a stalled trend, or side effects belong with the prescriber managing the treatment.
Sources
- New England Journal of Medicine. Once-weekly semaglutide in adults with overweight or obesity.
- PubMed. Changes in weight and glycemic control following obesity treatment with semaglutide or tirzepatide by discontinuation status.
- JAMA. Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance in adults with overweight or obesity: the STEP 4 randomized clinical trial.
- Nature Medicine. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial.
- Nature Medicine. Long-term weight loss effects of semaglutide in obesity without diabetes in the SELECT trial.
- Diabetes, Obesity and Metabolism. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. 2022.
- The Lancet Diabetes & Endocrinology. Once-weekly semaglutide 7.2 mg in adults with obesity (STEP UP): a randomised, controlled, phase 3b trial.
- US Food and Drug Administration. FDA approves fourth product under national priority voucher program, higher dose semaglutide.
- PubMed. Oral semaglutide at a dose of 25 mg in adults with overweight or obesity.
- PubMed. Semaglutide 2.4 mg once a week in adults with overweight or obesity, and type 2 diabetes (STEP 2): a randomised, double-blind, double-dummy, placebo-controlled, phase 3 trial.
- PubMed. Effect of weekly subcutaneous semaglutide vs daily liraglutide on body weight in adults with overweight or obesity without diabetes: the STEP 8 randomized clinical trial.
- TCTMD. Full SELECT results affirm CV risk reduction with semaglutide in nondiabetics. November 11, 2023.
Frequently asked questions
Is there a real week-by-week semaglutide weight loss chart from the trials?
No. STEP 1 reported its endpoints at week 68, STEP 5 at week 104, and SELECT through week 208. None of these trials published a week-by-week weight loss curve; the published record supports statements about weeks 68, 104 and 208, not week-by-week figures.
How much weight is typical in the first month on the starter dose?
The first four weeks use the 0.25 mg starter dose, a titration step toward the 2.4 mg maintenance dose reached by week 16.
When is the full maintenance dose reached?
In STEP 1, semaglutide started at 0.25 mg once weekly for the first 4 weeks, with the dose increased every 4 weeks to reach 2.4 mg weekly by week 16. Lower maintenance doses were permitted for participants with unacceptable side effects.
When do nausea and other GI effects usually hit and ease?
Nausea and diarrhea were the most common adverse events in STEP 1 — typically transient, mild-to-moderate, and subsiding with time. In STEP 5, 82.2% of the semaglutide group reported GI events versus 53.9% on placebo, mostly mild-to-moderate.
How many people quit in the first 3 months, and how does that change results?
In a real-world cohort of 7,881 patients who started injectable semaglutide or tirzepatide, people who discontinued within 3 months averaged 3.6% weight loss at one year, versus 6.8% for late discontinuation and 11.9% for those who did not discontinue (p < 0.001).
How much is lost at one year in trials versus real-world practice?
STEP 1 averaged −14.9% body weight at week 68. A real-world retrospective cohort of 7,881 patients who initiated injectable semaglutide or tirzepatide averaged 8.7% at one year, a gap the authors attributed to higher discontinuation rates and lower maintenance dosages.
Does weight loss keep going in year 2?
STEP 5 reported −15.2% at week 104. STEP 1, in a separate population, reported −14.9% at week 68. Neither trial reports a year-2 increment; the week-104 average sits close to the week-68 average, closer to a plateau than a continued slide.
How long does the plateau last if you stay on the drug?
In SELECT, weight loss continued over 65 weeks and was sustained for up to 4 years, with −10.2% at week 208 versus −1.5% for placebo (P < 0.0001). That 4-year follow-up is the longest in the cited trials.
This article summarizes FDA labeling, published research and company information current as of September 14, 2026. It is not medical advice and does not replace a conversation with your own healthcare provider. How we research and verify.