GLP-1 Weight Loss Timeline: Semaglutide and Tirzepatide
If you are wondering when you might start seeing results, here is what the FDA labels and the clinical trials actually say about timing. No trial can tell you your own timeline, but it can tell you what happened on average, and that is a more honest guide than a before-and-after photo.
One thing first: every figure on this page comes from trials of the manufacturers’ brand-name medicines, Wegovy (semaglutide) and Zepbound (tirzepatide). None of these trials studied compounded semaglutide or tirzepatide, and their results do not apply to compounded products.
The dose escalation reality
Before the timeline, here is the most important thing to understand: both medications start at a low dose and increase slowly. That is by design.
Wegovy injection (semaglutide): 0.25mg once weekly for weeks 1-4, then 0.5mg (weeks 5-8), 1mg (weeks 9-12), and 1.7mg (weeks 13-16). From week 17 on, the label’s usual maintenance dose for weight is 2.4mg weekly, and some adults who tolerate 2.4mg for at least 4 weeks may go up to 7.2mg[5]. The Wegovy tablet starts at 1.5mg daily and steps up every 30 days to a 25mg daily maintenance dose from day 91[5].
Zepbound (tirzepatide): 2.5mg once weekly for 4 weeks, then 5mg. After that, the dose may go up in 2.5mg steps after at least 4 weeks on the current dose. The maintenance dose for weight is 5mg, 10mg, or 15mg weekly. The label says the 2.5mg dose is for starting treatment and is not approved as a maintenance dose[6].
Both labels use this gradual schedule to lower the risk of stomach and bowel side effects[5][6]. Your prescriber sets the pace, and some people stay at a dose longer or stop at a lower maintenance dose depending on how they respond and what they tolerate. Knowing this up front can make the early weeks less discouraging.
Weeks 1-4: Starting and adapting
You are at the starting dose. Some people notice a change in appetite or in “food noise” (the constant mental pull toward food) right away; many notice little. Both experiences are common, and neither tells you much about how you will respond at higher doses.
Stomach and bowel side effects such as nausea, diarrhea, vomiting, and constipation are the most common side effects of both medications. In SURMOUNT-1 and SURMOUNT-5 they were mostly mild to moderate and happened mainly while the dose was being increased, and in STEP 1 nausea and diarrhea were typically temporary and eased with time[3][1][2]. If side effects are severe or do not let up, contact your prescriber. Severe vomiting or diarrhea can lead to dehydration, which both labels link to kidney problems[5][6].
Weight change during these first weeks is usually small. Be wary of anyone who promises a specific number of pounds this early.
Months 1-3: Doses escalating
Your dose is going up roughly every 4 weeks. On the Wegovy injection schedule, you move through 0.5mg, 1mg, and 1.7mg during this stretch. On the Zepbound schedule, you reach 5mg at week 5, the lowest maintenance dose, and may go higher after at least 4 more weeks on each dose[5][6].
This is the stretch where many people start to see the scale move, but the pace varies widely. Side effects can come back briefly after each dose increase, because the tirzepatide trials found they clustered during dose escalation[3][1].
If you miss doses, the timeline can shift. The Wegovy label says that if 2 or more weekly doses in a row are missed, the dose escalation should restart at a lower dose[5]. The Zepbound label says a missed dose can be taken within 4 days; after that, skip it and take the next dose on the regular day[6]. Ask your prescriber before restarting after a gap.
Months 3-6: Active weight loss
On the Wegovy injection schedule, the 2.4mg maintenance dose starts at week 17[5]. On Zepbound, the earliest you could reach 15mg is week 21, though many people stay at a lower maintenance dose[6].
One trial gives a useful snapshot of this period. In STEP 4, 902 adults without diabetes took semaglutide 2.4mg (Wegovy) during a 20-week run-in that included 16 weeks of dose increases. The 803 people who completed the run-in and reached 2.4mg had lost an average of 10.6% of their body weight by week 20[4]. Two cautions: everyone in the run-in took semaglutide (there was no placebo group yet), and the figure leaves out the 11% who stopped during the run-in, most often because of side effects. The Wegovy label notes that these results may not reflect the experience of people first starting the medication[5].
STEP 1 and SURMOUNT-1 also reported improvements in cardiometabolic risk factors along with the weight loss[2][3].
Months 6-12: Continued progress
Weight loss usually continues past six months but more slowly.
Two trials tracked the same people over time. In SURMOUNT-4, 783 adults without diabetes took Zepbound (tirzepatide), raised over up to 20 weeks to the highest dose they tolerated (10mg or 15mg). The 670 who completed the 36-week lead-in had lost an average of 20.9% of their body weight by week 36. Those who kept taking tirzepatide lost a further 5.5% from week 36 to week 88, for an average of 25.3% overall[7][6]. In STEP 4, people who kept taking semaglutide 2.4mg lost a further 7.9% from week 20 to week 68, after the 10.6% they lost in the first 20 weeks[4].
In both trials, the second stretch added less than the first, even though it was longer. A slowdown at this stage matches the trial pattern; it does not by itself mean the medication has stopped working. Some people plateau, lose a little more, then plateau again. Others lose steadily. If you plateau while on a maintenance dose, your prescriber can assess whether a dose change or another adjustment is appropriate.
Months 12-18: Approaching maintenance
The main weight loss trials ended in this window, with placebo groups for comparison:
- STEP 1 (Wegovy, semaglutide 2.4mg): 1,961 adults without diabetes. Average weight loss at 68 weeks was 14.9% with semaglutide and 2.4% with placebo, both alongside a lifestyle program. About half (50.5%) of people on semaglutide lost 15% or more[2].
- SURMOUNT-1 (Zepbound, tirzepatide): 2,539 adults without diabetes, including a 20-week dose-escalation period. Average weight loss at 72 weeks was 15.0% at 5mg, 19.5% at 10mg, and 20.9% at 15mg, compared with 3.1% with placebo[3].
Around this point, many people and their prescribers talk about the long term: staying on the current dose, adjusting it, or stopping. The trials are clear that stopping often leads to regain. In STEP 4, people switched from semaglutide to placebo at week 20 regained an average of 6.9% over the next 48 weeks, while those who continued lost a further 7.9%[4]. In SURMOUNT-4, people switched from tirzepatide to placebo at week 36 regained an average of 14.0% over the next 52 weeks, while those who continued lost a further 5.5%[7]. Plan any change with your prescriber.
Why some people see faster or slower results
The trial averages hide a wide range. Several things can differ from person to person:
Dose reached. In SURMOUNT-1, average weight loss was larger at 10mg and 15mg than at 5mg[3]. Some people stay at a lower dose because of side effects or because a lower dose is working for them.
Type 2 diabetes. In the Wegovy trial of adults with type 2 diabetes, average weight loss at 68 weeks was 9.6% with semaglutide 2.4mg versus 3.4% with placebo, smaller than in the trials of people without diabetes[5]. STEP 1, STEP 4, SURMOUNT-1, SURMOUNT-4, and SURMOUNT-5 all excluded people with diabetes[1][2][3][4][7].
Eating habits and activity. Both labels pair the medication with a reduced-calorie diet and increased physical activity, and the trials included lifestyle counseling[5][6]. If you are concerned about losing muscle along with fat, ask your prescriber or a dietitian about protein and strength training.
Staying on schedule. Missed doses and pauses can mean restarting the dose escalation, which pushes the timeline back[5].
Everything else. Sleep, stress, other medical conditions, and other medications vary from person to person. None of this is a reflection of how “well” you are doing.
Tirzepatide vs. semaglutide: The timeline difference
STEP 1 and SURMOUNT-1 were separate trials with different participants and lengths (68 vs. 72 weeks), so their results cannot be compared directly. The one trial that compared the two head to head is SURMOUNT-5.
In SURMOUNT-5, 751 adults with obesity but without type 2 diabetes took the highest dose they tolerated of tirzepatide (10mg or 15mg) or semaglutide (1.7mg or 2.4mg) once a week for 72 weeks. Average weight loss was 20.2% with tirzepatide and 13.7% with semaglutide[1]. The trial was open-label (people knew which medication they took) and was funded by Eli Lilly, which makes tirzepatide. It did not test the higher 7.2mg Wegovy dose now on the label[1][5].
These are averages. Some people do better on semaglutide than some people on tirzepatide. Both follow a similar pattern on the labels: low starting doses, increases every 4 weeks or more, then a maintenance dose. A licensed provider can talk through which fits your health history, coverage, and budget. For a fuller comparison, see semaglutide vs tirzepatide.
Side effects and safety at every stage
Benefits only tell half the story. Here is what the current labels say about risk.
Common side effects. The most common side effects of Wegovy include nausea, diarrhea, vomiting, constipation, abdominal pain, headache, fatigue, indigestion, dizziness, bloating, burping, low blood sugar in people with type 2 diabetes, gas, stomach flu, reflux, and hair loss[5]. The most common side effects of Zepbound include nausea, diarrhea, vomiting, constipation, abdominal pain, indigestion, injection site reactions, fatigue, allergic reactions, burping, hair loss, and reflux[6].
Boxed warning and who should not use them. Both labels carry a boxed warning about thyroid C-cell tumors seen in rodents. It is unknown whether either medication causes these tumors, including medullary thyroid carcinoma, in humans. Neither should be used by people with a personal or family history of medullary thyroid carcinoma or with Multiple Endocrine Neoplasia syndrome type 2, or by people with a known serious allergy to the medication[5][6].
Other warnings. Both labels also warn about acute pancreatitis, gallbladder disease, low blood sugar when used with insulin or sulfonylureas, kidney injury from dehydration, severe stomach and bowel reactions, serious allergic reactions, diabetic retinopathy complications in people with type 2 diabetes, and the risk of inhaling stomach contents during anesthesia or deep sedation. The Wegovy label also lists heart rate increase[5][6]. The Zepbound label advises people taking birth control pills to switch to a non-oral method, or add a barrier method, for 4 weeks after starting and for 4 weeks after each dose increase[6]. Both should be stopped if pregnancy is recognized when used for weight reduction[5][6].
For side-effect rates side by side, see semaglutide vs tirzepatide side effects.
What a proper weight loss program should include
The medication is one part of the timeline. The follow-up around it matters too, and programs differ in what they include. Before you sign up anywhere, check:
- Dose follow-up. Who decides when your dose goes up, and how you reach them if side effects make you want to slow down.
- Side-effect support. What happens if you have severe nausea, vomiting, or diarrhea, and how quickly you can get an answer.
- Labs and visits. Whether lab work and follow-up visits are included or billed separately.
- Nutrition and activity guidance. Some programs include coaching or dietitian support; others do not.
- Total cost over time. Prices vary by program and dose. Compare the total cost: medication, dose increases, visits, labs, shipping, membership fees, and cancellation terms. A low starting price can rise as the dose goes up.
- What is prescribed. Whether the program prescribes brand-name or compounded medication. Compounded semaglutide and tirzepatide are not FDA-approved, the FDA does not review them for safety, effectiveness, or quality, and they are not the same as Wegovy or Zepbound.
At most telehealth programs, a licensed provider reviews your health history and decides whether a prescription is appropriate, and which one.
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The reality: timelines vary
The timeline above reflects the FDA labels and what the trials reported on average. Your timeline might be different.
You might see changes sooner or later. You might plateau and then lose more. You might have more side effects in the first weeks, or very few. You might respond better to one medication than the other.
What the trials do show consistently: the labels start low and increase slowly, average weight loss built over months rather than weeks, the pace slowed later in treatment, and stopping the medication often led to regain[2][3][4][7]. Knowing that pattern can help you judge your own progress against the actual evidence, not against hype or a timeline that does not apply to you.
Weeks 1-4: Starting and adapting
Starting doses: Wegovy injection 0.25mg weekly, Zepbound 2.5mg weekly. These doses are for getting started, not for long-term use. Nausea and other stomach and bowel side effects are most common during dose increases. Weight changes are usually small.
Months 1-3: Escalating doses
Doses increase every 4 weeks (Wegovy) or after at least 4 weeks (Zepbound). Zepbound reaches 5mg, its lowest maintenance dose, at week 5. Side effects can return briefly after each increase.
Months 3-6: Active weight loss
Wegovy injection reaches its 2.4mg maintenance dose at week 17. In STEP 4, people who completed a 20-week semaglutide run-in had lost an average of 10.6% by week 20.
Months 6-12: Continued progress
In SURMOUNT-4, people who completed a 36-week tirzepatide lead-in had lost an average of 20.9%. In both STEP 4 and SURMOUNT-4, loss continued afterward but more slowly.
Months 12-18: Maintenance transition
STEP 1: 14.9% vs 2.4% with placebo at 68 weeks. SURMOUNT-1: 15.0% to 20.9% by dose vs 3.1% with placebo at 72 weeks. Stopping often led to regain in STEP 4 and SURMOUNT-4. Results vary.
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Get StartedThis content is for general education and is not medical advice. Talk with a licensed provider about your situation.
Results vary. Trial results describe study participants and are not a prediction for any individual. The timeline figures on this page come from trials of FDA-approved brand-name semaglutide (Wegovy) and tirzepatide (Zepbound).
Compounded medications are not FDA-approved. The FDA does not review them for safety, effectiveness, or quality. Compounded semaglutide and tirzepatide are not the same as brand-name products such as Wegovy or Zepbound. They may differ in formulation, purity, and potency.
Wegovy is a trademark of Novo Nordisk A/S. Zepbound is a trademark of Eli Lilly and Company. Transformation Health is not affiliated with or endorsed by these companies.
Citations
[1] Aronne LJ, Horn DB, le Roux CW, et al. “Tirzepatide as Compared with Semaglutide for the Treatment of Obesity.” N Engl J Med. 2025;393(1):26-36. https://pubmed.ncbi.nlm.nih.gov/40353578/ (SURMOUNT-5: 20.2% vs 13.7% at 72 weeks; side effects mainly during dose escalation; funding.)
[2] Wilding JPH, Batterham RL, Calanna S, et al. “Once-Weekly Semaglutide in Adults with Overweight or Obesity.” N Engl J Med. 2021;384(11):989-1002. https://pubmed.ncbi.nlm.nih.gov/33567185/ (STEP 1: 14.9% vs 2.4% at 68 weeks.)
[3] Jastreboff AM, Aronne LJ, Ahmad NN, et al. “Tirzepatide Once Weekly for the Treatment of Obesity.” N Engl J Med. 2022;387(3):205-216. https://pubmed.ncbi.nlm.nih.gov/35658024/ (SURMOUNT-1: 15.0%, 19.5%, 20.9% vs 3.1% at 72 weeks, including a 20-week dose-escalation period.)
[4] 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. https://pubmed.ncbi.nlm.nih.gov/33755728/ (10.6% during the 20-week run-in; -7.9% continued vs +6.9% placebo from week 20 to 68.)
[5] U.S. Food and Drug Administration. WEGOVY (semaglutide) injection and tablets, prescribing information. Revised 06/2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/215256s025lbl.pdf
[6] U.S. Food and Drug Administration. ZEPBOUND (tirzepatide) injection, prescribing information. Revised 08/2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/217806Orig1s041correctedlbl.pdf
[7] Aronne LJ, Sattar N, Horn DB, et al. “Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial.” JAMA. 2024;331(1):38-48. https://pubmed.ncbi.nlm.nih.gov/38078870/ (20.9% during the 36-week lead-in; -5.5% continued vs +14.0% placebo from week 36 to 88; 25.3% overall at week 88.)