GLP-1 Weight Loss Results by Month: What Trials Show

Published on

September 29, 2026

Written by

Bodly Team

If you have just started Wegovy, Zepbound or Mounjaro, you probably want to know one thing: is my weight loss normal? Social media is full of dramatic month-one results and frustrating stalls. The clinical trials give a more reliable picture.

This guide summarizes what the major trials found, month by month and per week, what the first month usually looks like, and how to track your own results against them.

This article is for general information and is not medical advice. GLP-1 medications must be prescribed and monitored by a licensed clinician. Never change your dose based on an article or calculator.

The short answer

Medication (trial)	Dose	Trial length	Average weight loss	Average per week
Semaglutide, Wegovy (STEP 1)	2.4 mg weekly	68 weeks	14.9% (placebo 2.4%)	~0.2%
Tirzepatide, Zepbound / Mounjaro (SURMOUNT-1)	5 mg weekly	72 weeks	15.0%	~0.2%
Tirzepatide (SURMOUNT-1)	10 mg weekly	72 weeks	19.5%	~0.3%
Tirzepatide (SURMOUNT-1)	15 mg weekly	72 weeks	20.9% (placebo 3.1%)	~0.3%
Retatrutide (phase 2, investigational)	12 mg weekly	48 weeks	24.2% (placebo 2.1%)	~0.5%

"Average per week" is simply the total divided by the number of weeks. In reality, weight loss is slow at first, fastest in the middle months and slows down as it approaches a plateau.

All trial participants also received lifestyle support (a reduced-calorie diet and physical activity guidance), and these are averages: in every trial, some people lost much more and some much less.

To see what these averages would mean at your starting weight, week by week, try our GLP-1 weight loss calculator. Our body visualizer shows the same change as a before-and-after outline.

Month by month: what the typical curve looks like

Month 1: the slowest month

Both semaglutide and tirzepatide start at a low dose that increases every four weeks. Semaglutide begins at 0.25 mg and tirzepatide at 2.5 mg. These starting doses are mainly there to let your body get used to the medication and limit side effects, not to cause maximum weight loss.

So the first month is typically the slowest. Some of the loss you do see is water, as eating less reduces stored carbohydrate and the water that comes with it. That is why comparing your month one with someone's viral month-four photo is not useful.

The standard dose schedule

This is the usual step-up in the US labels. Your prescriber may keep you on a dose longer, or stop at a lower maintenance dose, depending on how you respond and how you tolerate it.

Weeks	Wegovy (semaglutide)	Zepbound / Mounjaro (tirzepatide)
1-4	0.25 mg	2.5 mg
5-8	0.5 mg	5 mg
9-12	1 mg	7.5 mg
13-16	1.7 mg	10 mg
17-20	2.4 mg (maintenance)	12.5 mg
21+	2.4 mg	15 mg (maintenance doses: 5, 10 or 15 mg)

In other words, most people do not reach a full dose until month four or five, which is why the first three months look so different from the rest of the year.

Months 2 to 4: the dose climbs

As doses step up, appetite usually falls further and weight loss picks up. Side effects such as nausea are also most common while doses are increasing.

Months 4 to 12: the steepest stretch

Once people reach their maintenance dose, weight loss tends to be at its most consistent. For many, this is where most of the total loss happens.

Month 12 and beyond: the plateau

In STEP 1, weight loss on semaglutide continued until about week 60 and then leveled off. A plateau after a year or so is expected. It is your body settling at a new, lower weight, not the medication "stopping working".

What the average curve means in pounds

Percentages are hard to picture, so here is the average trial curve from our GLP-1 weight loss calculator applied to three starting weights. These are averages, not predictions: about half of people lose more and half lose less.

Tirzepatide 15 mg (Zepbound, Mounjaro):

Starting weight	Month 1	Month 3	Month 6	Month 12
200 lb	194 lb	181 lb	169 lb	160 lb
250 lb	242 lb	226 lb	211 lb	200 lb
300 lb	291 lb	272 lb	253 lb	239 lb

Semaglutide 2.4 mg (Wegovy):

Starting weight	Month 1	Month 3	Month 6	Month 12
200 lb	196 lb	186 lb	177 lb	171 lb
250 lb	245 lb	233 lb	222 lb	214 lb
300 lb	293 lb	280 lb	266 lb	257 lb

So "Zepbound results after 1 month" for a 250 lb person on average means around 8 lb, a lot of it water. The big numbers you see in before-and-after posts usually come from months 4 to 12.

Zepbound and Mounjaro results in more detail

Zepbound and Mounjaro contain the same drug, tirzepatide. In the SURMOUNT-1 trial, adults with obesity or overweight (without diabetes) lost on average:

15.0% of their body weight on 5 mg
19.5% on 10 mg
20.9% on 15 mg

over 72 weeks, compared with 3.1% on placebo (Jastreboff et al., 2022). For someone starting at 100 kg (220 lb), a 20.9% loss would mean about 21 kg (46 lb) over roughly 17 months.

People with type 2 diabetes usually lose somewhat less weight on the same medications than people without diabetes, so if you take Mounjaro for diabetes, the SURMOUNT-1 numbers are an optimistic benchmark.

Wegovy and Ozempic results

Wegovy and Ozempic contain semaglutide. In the STEP 1 trial, adults taking semaglutide 2.4 mg once weekly lost an average of 14.9% of their body weight over 68 weeks, against 2.4% on placebo (Wilding et al., 2021). Ozempic's maximum dose for diabetes is lower than Wegovy's 2.4 mg, so results are not directly comparable.

What about retatrutide?

Retatrutide is a newer "triple agonist" that acts on GLP-1, GIP and glucagon receptors. It is investigational and not approved for any use as of September 2026.

In its phase 2 trial, average weight loss at 48 weeks ranged from 8.7% on 1 mg to 24.2% on 12 mg, against 2.1% on placebo (Jastreboff et al., 2023). The manufacturer has since reported phase 3 results with even larger losses. Retatrutide sold online outside of a prescription or trial is unregulated. Do not use it.

Why your results may differ from the trials

Dose. Higher doses produced more weight loss in every trial.
Diabetes. People with type 2 diabetes tend to lose less.
Starting weight. A heavier starting weight often means more kilograms lost, even at the same percentage.
Muscle. Some weight loss on GLP-1s is lean mass, not fat. See why GLP-1s cause muscle loss for how to protect it.
Protein, strength training and sleep all shape what kind of weight you lose.
Individual response. Averages hide a wide range: some people lose far more, some far less.

How to track your GLP-1 results properly

The scale alone can mislead you on a GLP-1, especially in the first weeks when water shifts are large, and later when fat loss slows. Track a few things together:

Weigh yourself regularly and watch the weekly average, not single days. Our guide to the whoosh effect explains why the scale can stall and then drop.
Measure your waist and hips every two to four weeks. How to take body measurements shows the method.
Take progress photos in the same light and pose every few weeks.
Log your protein. Hitting a protein target is one of the best ways to keep the weight you lose mostly fat. Our protein intake calculator gives you a range to discuss with your clinician.
Note your dose changes so you can see how your weight responded to each step.

Bodly is built for exactly this: a smoothed weight trend, tape measurements, side-by-side progress photos and AI photo meal logging in one app, so you can see whether you are losing fat, not just weight.

Bottom line

In the trials, people lost an average of about 15% of their body weight on semaglutide 2.4 mg over 68 weeks and 15% to 21% on tirzepatide over 72 weeks, with the first month the slowest and a plateau after about a year. That works out to roughly 0.2% to 0.3% of body weight per week on average, faster in the middle months.

Use these numbers as a rough benchmark, not a target. Track your weekly average, measurements and photos, protect your muscle with protein and strength training, and discuss any concerns about your progress with the clinician who prescribes your medication.

Keep reading

Why GLP-1s cause muscle loss: how to lose fat without losing strength.
The whoosh effect: why the scale stalls and then drops.
Metabolic adaptation: why weight loss slows down over time.

Sources

Frequently asked questions

How much weight do you lose on Zepbound in 3 months?

On the average SURMOUNT-1 curve for the 15 mg dose, about 9 to 10% of starting weight after three months: roughly 19 lb from 200 lb or 24 lb from 250 lb. Remember that doses are still stepping up during these months, and individual results vary widely.

How much weight do you lose in the first month on Zepbound or Mounjaro?

The first month is usually the slowest, because tirzepatide starts at a low 2.5 mg dose and is increased every four weeks. Some early loss is water. The trials show weight loss picking up once people reach higher doses, then continuing for over a year. Your own first month depends on your starting weight, dose, diet and activity, so compare yourself with your own trend rather than someone else's first month.

What is the average weight loss per week on tirzepatide?

In the SURMOUNT-1 trial, people on the highest dose (15 mg) lost an average of 20.9% of their body weight over 72 weeks, which averages out to about 0.3% of body weight per week. Loss is faster in the middle months and slows toward the end, so actual weekly losses vary a lot over time.

How much weight do people lose on Wegovy?

In the STEP 1 trial, adults taking semaglutide 2.4 mg once a week (Wegovy's dose) together with lifestyle support lost an average of 14.9% of their body weight over 68 weeks, compared with 2.4% on placebo. Weight loss continued until about week 60 and then leveled off.

How much weight do people lose per week on retatrutide?

Retatrutide is still investigational and not approved as of September 2026. In its phase 2 trial, the highest dose (12 mg) produced an average loss of 24.2% of body weight over 48 weeks, about 0.5% per week on average. Phase 3 results reported by the manufacturer are even larger. Only use GLP-1 medications prescribed by a licensed clinician.

Are Zepbound and Mounjaro the same?

Both contain tirzepatide. Mounjaro is approved for type 2 diabetes and Zepbound for chronic weight management (and some other conditions). Similarly, Ozempic and Wegovy both contain semaglutide: Ozempic for type 2 diabetes and Wegovy for weight management, at a higher maximum dose.