Calculate weight loss with GLP-1
Curious how much you could lose with GLP-1 medication? This calculator shows an indicative trajectory based on averages from clinical research, per medication. It is meant as information, not as a personal prediction or medical advice.
Disclaimer: The information on this page is intended for general information purposes only and is not medical advice. The figures shown are averages from clinical research; individual results vary. Always consult a doctor before starting any medication. GLP-1 medication is available on prescription only and must be used under professional medical supervision.
How this calculation works
The calculator does not use a personal formula, but the average weight loss from the large clinical trials of these medications. For each medication we show a band between two figures: the average across everyone who took part, and the average among people who used the medication as prescribed. That gives you a realistic range instead of a single flattering number.
The trajectory over time follows the shape seen in the trials: weight falls fastest in the first months, then flattens toward a plateau. We never extrapolate beyond the trial duration, and the dashed line shows what the placebo group in the same trials achieved on average with lifestyle alone (STEP 1 about 2.4%, SURMOUNT-1 about 3.1%).
How much you lose yourself depends on your starting weight, your lifestyle, other conditions and how your body responds to the medication. An average from research is a guide, not a promise. That is why we always show a range and cite the source for every figure.
How much you lose per medication
Below are the four GLP-1 medications used for weight loss, each with the average loss from its trial. The trials differ in design and duration, so the figures cannot be compared one to one.
How much weight do you lose with Mounjaro (tirzepatide)?
Mounjaro contains tirzepatide and acts on two hormone systems, GIP and GLP-1. The figure above comes from the SURMOUNT-1 trial in people with obesity without diabetes, measured at 72 weeks. The medication is injected weekly and the dose is built up step by step.
How much weight do you lose with Ozempic (semaglutide)?
Ozempic contains semaglutide and is registered for the treatment of type 2 diabetes; for weight loss it is used off-label, up to a dose of 2.0 mg. Wegovy contains the same active substance at a higher dose and does have its own registration for weight loss. Reliable weight-loss figures are therefore about Wegovy, not Ozempic.
How much weight do you lose with Saxenda (liraglutide)?
Saxenda contains liraglutide and is registered for weight loss. The figure above comes from the SCALE trial, measured at 56 weeks. Unlike the other options, Saxenda is injected daily rather than weekly, and the dose is built up gradually.
How much weight do you lose with Wegovy (semaglutide)?
Wegovy contains semaglutide and is registered for weight loss. The figure above comes from the STEP 1 trial in people with overweight or obesity, measured at 68 weeks. It is the same active substance as in Ozempic, but in a higher dose studied for weight management.
The medications were studied in different trials, with different participants and measurement methods. A higher figure therefore does not automatically mean a medication works better for you. A doctor decides which medication is appropriate.
Side effects and conditions
GLP-1 medication is not something you take casually. It can cause side effects and is not suitable for everyone. A registered doctor always assesses first whether it is responsible.
- Common side effects
- Nausea, constipation, diarrhoea and a full feeling are the most common, especially in the first weeks and when increasing the dose. They usually ease as your body adjusts.
- Not for everyone
- The medication is generally intended from a BMI of 30, or from 27 in combination with a weight-related condition. At a lower BMI, medication is usually not appropriate.
- Contra-indications
- It is not suitable in cases such as pregnancy, a history of certain thyroid cancers or pancreatitis. That is why the doctor reviews your medical situation in advance.
- Under supervision
- The dose is built up slowly and your use is monitored. That keeps side effects more manageable and allows for timely adjustment.
Always read the official package leaflet and discuss your situation with a doctor. This page does not replace that conversation.
What happens if you stop
GLP-1 medication treats weight for as long as you use it; it is not a one-off course. In the follow-up to the STEP 1 trial, most of the lost weight returned within a year after people stopped the medication and the guidance.
That does not mean it is pointless. Above all it shows that lasting results take more than medication alone: attention to nutrition, movement and habits you can keep up without the medication too. That is what a good guidance programme focuses on.
Wondering whether medically supervised weight loss suits you? Take the free check.
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with GLP-1 medication.
- How much weight do you lose with Wegovy?
- In the STEP 1 trial the average loss at 68 weeks was 14.9 to 16.9% of body weight. Fill in the calculator above for an estimate based on your weight, or read more about the medication.
- How quickly do you see results with Mounjaro?
- In the trials weight falls fastest in the first months and then flattens. The calculator shows that trajectory for the time horizon you choose.
- Do you lose more with Mounjaro than with Wegovy?
- On average the loss was higher in the Mounjaro trial, but the trials are not directly comparable due to differences in participants, design and duration. A doctor assesses which medication suits you.
- What is the difference between Ozempic and Wegovy?
- Both contain semaglutide. Ozempic is registered for type 2 diabetes and used off-label for weight loss; Wegovy has its own registration for weight loss in a higher dose. Read more about the medications.
- Do you stay at your weight after stopping?
- Research shows that much of the weight returns without further guidance. A programme that also looks at your BMI and lifestyle helps you keep the result. Take the free check to see whether it suits you.
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