GLP-1 Results Timeline Calculator

The GLP-1 Weight Loss Timeline Calculator projects the expected trajectory of weight loss for patients taking glucagon-like peptide-1 (GLP-1) receptor agonist medications, specifically semaglutide (marketed as Ozempic and Wegovy) and tirzepatide (marketed as Mounjaro and Zepbound). These medications have transformed the treatment of obesity and type 2 diabetes since their approval, producing average total body weight losses of 15 to 22 percent over 68 to 72 weeks in pivotal clinical trials. The calculator uses published dose-escalation schedules and weight-loss curves from the STEP and SURMOUNT trial programs to model expected results at each treatment milestone. GLP-1 receptor agonists work by mimicking the incretin hormone GLP-1, which is naturally released from the gut after eating. The medication slows gastric emptying, reduces appetite through hypothalamic signaling, and improves insulin sensitivity. Tirzepatide additionally activates the glucose-dependent insulinotropic polypeptide (GIP) receptor, providing a dual-agonist mechanism that produces somewhat greater weight loss than semaglutide alone. Both medications are administered as once-weekly subcutaneous injections and require gradual dose escalation over 16 to 20 weeks to minimize gastrointestinal side effects. The calculator is designed for patients and healthcare providers who want a realistic preview of the weight loss journey, including the slow initial phase during dose escalation, the acceleration at therapeutic doses, the typical plateau at 60 to 72 weeks, and the expected weight regain if the medication is discontinued. It also models the impact of lifestyle factors (diet, exercise, baseline BMI) on the trajectory, drawing on subgroup analyses from the clinical trials. This tool does not replace medical advice. GLP-1 medications require a prescription, ongoing medical monitoring, and attention to potential side effects including nausea, vomiting, diarrhea, constipation, pancreatitis risk, and thyroid concerns. The calculator provides population-level estimates based on clinical trial averages; individual results vary significantly based on genetics, adherence, concurrent medications, and lifestyle factors.

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1. 1The user enters baseline demographics: starting weight (pounds or kilograms), height, age, sex, and starting BMI (auto-calculated from weight and height). The calculator validates that the patient meets the FDA-approved indication criteria: BMI of 30 or greater, or BMI of 27 or greater with at least one weight-related comorbidity (type 2 diabetes, hypertension, dyslipidemia, or obstructive sleep apnea).
2. 2The user selects the medication: semaglutide 2.4 mg (Wegovy), semaglutide 1.0 mg (Ozempic, used off-label for weight loss), tirzepatide 5 mg, 10 mg, or 15 mg (Zepbound/Mounjaro). Each medication has a distinct dose-escalation schedule and published efficacy curve. The calculator loads the corresponding trial data: STEP 1 through STEP 5 for semaglutide, SURMOUNT-1 through SURMOUNT-4 for tirzepatide.
3. 3The dose-escalation schedule is displayed as a timeline. For semaglutide (Wegovy), escalation proceeds: 0.25 mg (weeks 1-4), 0.5 mg (weeks 5-8), 1.0 mg (weeks 9-12), 1.7 mg (weeks 13-16), 2.4 mg (week 17 onward). For tirzepatide (Zepbound), escalation proceeds: 2.5 mg (weeks 1-4), 5.0 mg (weeks 5-8), 7.5 mg (weeks 9-12), 10.0 mg (weeks 13-16), 12.5 mg (weeks 17-20), 15.0 mg (week 21 onward if tolerated). Weight loss during escalation is modest, approximately 2 to 5 percent of starting weight.
4. 4The calculator models the weight-loss curve using a modified exponential decay function fitted to the published trial data. The curve shows rapid loss during weeks 16 through 40 (approximately 1.0 to 1.5 percent of body weight per month), gradual deceleration during weeks 40 through 60, and a plateau approaching the maximum effect between weeks 60 and 72. The STEP 1 trial showed semaglutide 2.4 mg producing a mean loss of 14.9 percent at week 68; SURMOUNT-1 showed tirzepatide 15 mg producing a mean loss of 22.5 percent at week 72.
5. 5Lifestyle modifier inputs adjust the projection. Patients who combine the medication with a structured diet (500 kcal/day deficit) and exercise program (150+ minutes/week of moderate activity) typically achieve 2 to 4 percentage points more weight loss than medication alone. The STEP 3 trial, which combined semaglutide with intensive behavioral therapy, showed 16.0 percent weight loss versus 14.9 percent with medication alone. The calculator applies these modifiers to the base curve.
6. 6A discontinuation scenario is optionally modeled. The STEP 1 extension study showed that patients who stopped semaglutide regained approximately two-thirds of the lost weight within one year of discontinuation. The calculator projects this regain trajectory, showing the expected weight at 6, 12, and 24 months post-discontinuation. This information helps patients and providers plan for long-term medication adherence or transition strategies.
7. 7The output is a week-by-week chart showing projected weight, cumulative pounds lost, cumulative percent lost, current dose, and monthly cost at list price and with common insurance coverage tiers. A summary table highlights key milestones: 5 percent weight loss (the threshold for clinically meaningful health benefits), 10 percent (associated with significant metabolic improvement), 15 percent (associated with NAFLD resolution in many patients), and 20+ percent (achievable with tirzepatide 10-15 mg, associated with potential diabetes remission).

• !The most common misconception is expecting linear weight loss throughout treatment. GLP-1 weight loss follows a logarithmic curve: minimal loss during the 16 to 20 week dose-escalation period, rapid loss during the therapeutic-dose phase (weeks 16-48), and gradual plateauing as the body reaches a new metabolic set point (weeks 48-72). Patients who expect steady 2-pound-per-week losses from week one will become frustrated during escalation and may discontinue prematurely.
• !Another frequent error is comparing results to clinical trial averages without understanding the distribution. The STEP 1 mean of 14.9 percent weight loss represents an average across a wide range of individual responses. Approximately 30 percent of patients achieve less than 10 percent weight loss, while approximately 30 percent achieve more than 20 percent. Factors that predict better response include female sex, lower baseline BMI, younger age, stronger adherence to lifestyle changes, and fewer concurrent medications that promote weight gain.
• !Many patients and providers underestimate the importance of the dose-escalation schedule. Skipping escalation steps or rapidly increasing doses to reach the therapeutic level faster significantly increases the risk of severe nausea, vomiting, and gastroparesis. The escalation protocol was specifically designed during clinical trials to allow the gastrointestinal system to adapt. Patients who cannot tolerate a given dose should remain at that dose for an additional 4 weeks before attempting escalation rather than jumping ahead.