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GLP-1 Weight Loss Calculator: Semaglutide and Tirzepatide

In clinical trials of the FDA-approved brand-name medications, adults taking semaglutide lost an average of about 15% of their body weight over 68 weeks, and adults taking tirzepatide lost an average of about 20% over 72 weeks. This calculator applies those published trial averages to your current weight to show a range of outcomes, not a prediction of your own. Individual results varied widely, roughly 1 in 7 participants lost less than 5%, and Protocol MD's GLP-1 is compounded, which is not FDA-approved and not the same product studied in those trials.

Medication

Each medication has its own trial and its own response distribution. Nothing is preselected.

Sex

Used only to describe your BMI in context. The adult BMI cutoffs are identical for men and women, and sex is not an input to the projection.

The trials enrolled adults. Age is not an input to the projection.

Height

Results update as you type. The button is here for keyboard and screen-reader users, and pressing Enter does the same thing.

Your inputs stay in your browser. Nothing you type here is sent to us, saved to an account, stored, or emailed. Like any page on this site, we do record that the page was visited.

Your range appears here as soon as every field is filled in. Nothing is submitted, nothing is sent, and there is no email step.

Not for use during pregnancy or breastfeeding, under 18, or while being treated for an eating disorder. Talk to your physician first.

Educational only. This tool does not diagnose, prevent, treat, or cure any condition, and it is not medical advice or a recommendation of any specific therapy.

These numbers are estimates produced by a published equation. Individual needs vary. Talk with a licensed physician before making changes to how you eat, train, or take medication.

Using this calculator does not create a physician-patient relationship with Protocol MD.

Not for use during pregnancy or breastfeeding, under 18, or while being treated for an eating disorder. Talk to your physician first.

If tracking calories or weight feels compulsive or distressing, that is worth raising with a clinician. In the US you can text "NEDA" to 741741 to reach a trained volunteer at Crisis Text Line, any time.

Your inputs stay in your browser. Nothing you type here is sent to us, saved to an account, stored, or emailed. Like any page on this site, we do record that the page was visited.

What This Calculator Does, And What It Cannot Do

It does one thing. It takes the percentage of body weight that participants lost in a published clinical trial, applies that percentage to the weight you entered, and shows you where the arithmetic lands. That is the whole model. There is no algorithm behind it, no adjustment for your metabolism, and no attempt to guess where in the distribution you would fall.

What it cannot do follows directly from that. It cannot predict your outcome, because the trials it draws from reported a wide spread rather than a single result: some participants lost a quarter of their body weight, and roughly 1 in 7 lost less than 5%. Nothing measurable in advance reliably sorts one group from the other. It also cannot see your medical history, your other medications, how well you tolerate the drug, or whether you would still be taking it a year later, and every one of those changes the answer more than the arithmetic does.

Read the range as context for a conversation, not as a forecast. If you want the underlying screening number on its own, the BMI calculator shows it with a full account of its limits, and the calorie calculator estimates daily energy needs, which is a separate question from what any medication would do. All of them, and the rest of the free health calculators, run entirely in your browser.

What The Trials Actually Found

Two trials sit behind every number on this page. Both studied the FDA-approved brand-name products, both ran for well over a year, and both paired the medication with structured lifestyle support rather than testing the drug on its own.

Semaglutide: STEP-1, 68 Weeks

Participants taking semaglutide lost an average of about 14.9% of their body weight over 68 weeks, against about 2.4% in the placebo group. The distribution matters more than the average: roughly half lost 15% or more, about a third lost 20% or more, and around 1 in 7 lost less than 5%. See Wilding JPH, et al., Once-weekly semaglutide in adults with overweight or obesity, New England Journal of Medicine 2021 (STEP-1) for the full results.

Tirzepatide: SURMOUNT-1, 72 Weeks

Participants taking tirzepatide lost an average of about 15% to 20.9% of their body weight over 72 weeks, depending on the dose studied, against about 3.1% on placebo. About half lost 20% or more at the higher doses. See Jastreboff AM, et al., Tirzepatide once weekly for the treatment of obesity, New England Journal of Medicine 2022 (SURMOUNT-1) for the full results.

Both Trials Included Lifestyle Support

This is the part that gets dropped when trial averages are quoted in marketing. Participants in both studies received a reduced-calorie eating plan and were asked to increase physical activity, with regular counselling alongside the medication. The published figures describe that whole package. They do not describe a medication taken on its own, and this calculator cannot separate the two, because the trials did not.

Why Compounded Is Not The Same As The Brand

These results come from trials of the FDA-approved brand-name products. Protocol MD's semaglutide and tirzepatide are compounded. Compounded medications are not FDA-approved, are not generic equivalents of, and are not the same product as, the brand-name medications studied in these trials.

Stated plainly: a compounded medication is prepared by a licensed compounding pharmacy for an individual patient. FDA does not review compounded drugs for safety, effectiveness, or quality before they are dispensed, and a compounded preparation is not a generic. A generic is an approved copy that has been shown to be equivalent to the brand. A compounded preparation has not been through that process.

That distinction is why the numbers above are labelled as trial results rather than as anything this practice is offering you. If you want to see what compounded GLP-1 through Protocol MD actually involves, that page sets out the terms, and how semaglutide and tirzepatide differ covers the comparison in more depth.

Who These Trials Enrolled

Both trials enrolled adults with a BMI of 30 or higher, or 27 or higher with at least one weight-related health condition. Nobody below that range was studied, so there is no published average to apply to anyone below it.

That is the reason this calculator stops rather than extrapolating. Below a BMI of 27 it shows no projected number at all, because running the arithmetic anyway would take a figure from a population you were not part of and present it as though it described you. A tool that produces a number for everyone who asks is easier to build and worse at its job.

Meeting the enrolment criteria of a trial is also not the same as being an appropriate candidate for treatment. That assessment includes your medical history, current medications, and contraindications, and only a licensed physician can make it.

What Happens If You Stop

Weight regain after stopping is common. In a follow-up of the semaglutide trial, participants regained about two-thirds of their lost weight in the year after treatment ended.

The follow-up study is worth reading before starting rather than after. One year after treatment and lifestyle support were withdrawn, participants had regained roughly two-thirds of the weight they had lost, and most of the improvements in cardiometabolic markers moved back toward baseline with it. See Wilding JPH, et al., Weight regain and cardiometabolic effects after withdrawal of semaglutide, Diabetes, Obesity and Metabolism 2022.

The practical implication is that these medications are studied as ongoing treatment, not as a course you finish. What that means for cost, for duration, and for what happens if you stop is a conversation to have with a physician at the start, not eighteen months in.

How Protocol MD Approaches GLP-1 Care

Protocol MD is a physician-guided practice. A licensed physician reviews your intake, your medical history, and your current medications, and decides whether treatment is appropriate. Nothing is prescribed on the basis of a calculator, a quiz score, or a number on this page, and a physician can decline.

If a physician does determine that treatment is appropriate, what is dispensed is compounded semaglutide or tirzepatide, prepared by a licensed compounding pharmacy, with the disclosures set out above. Compounded medications are not FDA-approved. If you are still deciding between the two molecules, the comparison of semaglutide and tirzepatide lays out what is known about each.

If that is the conversation you want to have, you can start the medical assessment. It takes a few minutes and a physician reviews it.

Frequently Asked Questions

How much weight can you lose on semaglutide?

In the STEP-1 trial, adults taking semaglutide lost an average of about 14.9% of their body weight over 68 weeks. Roughly half lost 15% or more and about a third lost 20% or more, but around 1 in 7 lost less than 5%. These are averages from a trial of the FDA-approved brand-name product, not a prediction for any individual.

How much weight can you lose on tirzepatide?

In the SURMOUNT-1 trial, adults taking tirzepatide lost an average of about 15% to 20.9% of their body weight over 72 weeks depending on the dose studied. About half lost 20% or more at the higher doses. Individual results varied widely and a physician determines what is appropriate for you.

Is this calculator accurate?

It is arithmetic applied to published trial averages, so it is only as applicable as those averages are to you. It cannot account for your metabolism, medical history, medication tolerance, or adherence. Treat the range as context for a conversation with a physician, not as a forecast.

How long does it take to lose weight on a GLP-1?

In both trials the full result took roughly 68 to 72 weeks, about 16 to 17 months. Loss was gradual, steepest in the earlier months, and flattened toward the end of the study period.

Will I gain the weight back if I stop?

Weight regain after discontinuation is commonly reported. In a follow-up of the semaglutide trial, participants regained about two-thirds of the weight they had lost within a year of stopping. This is worth discussing with your physician before starting.

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Educational only. This tool does not diagnose, prevent, treat, or cure any condition, and it is not medical advice or a recommendation of any specific therapy.

Using this calculator does not create a physician-patient relationship with Protocol MD.