GLP-1 Response Estimator
Project your trajectory on semaglutide or tirzepatide with realistic dose titration. Not a flat-dose fantasy.
Uncheck a step to stay at the previous dose. All later steps will also turn off.
e.g., 7.2. If blank, uses 7.5%
e.g., 110. If blank, uses 120 mg/dL
e.g., 220. If blank, uses 200 lb
How this works
GLP-1 receptor agonists are prescribed with stepwise dose titration, not as a flat dose. You start low and increase every 4 weeks to reduce GI side effects (nausea, vomiting, diarrhea) and let your body adapt. This calculator models that real-world pattern: your projected trajectory changes shape at each dose step, because the response parameters change with the dose.
Semaglutide (brand names Ozempic for type 2 diabetes, Wegovy for weight management) is a GLP-1 receptor agonist. Tirzepatide (Mounjaro for diabetes, Zepbound for weight management) is a dual GIP/GLP-1 receptor agonist. Both slow gastric emptying, reduce appetite through central mechanisms, and improve insulin sensitivity. Tirzepatide's dual action on GIP and GLP-1 receptors produces greater weight loss and A1c reduction than semaglutide alone.
The response data behind these projections comes from large Phase III randomized controlled trials. For semaglutide: the SUSTAIN program (type 2 diabetes, over 8,000 participants across trials) and the STEP program (weight management, over 4,500 participants). For tirzepatide: the SURPASS program (diabetes, over 9,000 participants) and the SURMOUNT program (weight management, over 5,000 participants). SURMOUNT-5, a head-to-head comparison, showed tirzepatide 15 mg produced 20.2% weight loss versus 13.7% for semaglutide 2.4 mg at 72 weeks.
Weight loss follows an exponential approach to plateau. Most loss occurs in the first 40 weeks; the curve flattens as the body approaches a new equilibrium. A1c reductions typically plateau by 16 to 20 weeks. Semaglutide at 1.0 mg reduces A1c by roughly 1.5 points from baseline; tirzepatide at 15 mg by roughly 2.2 points. Fasting glucose tracks directionally with A1c but moves faster, often dropping measurably within the first 4 to 8 weeks.
Why the confidence band is wide: in STEP 1, the interquartile range for semaglutide 2.4 mg weight loss was roughly 10% to 20%, meaning a quarter of participants lost less than 10% and a quarter lost more than 20%. Genetics, baseline insulin resistance, medication adherence, diet quality, exercise habits, and sleep all contribute to where you land in that range. Higher baseline A1c predicts larger absolute A1c reduction but smaller percentage weight loss, because greater insulin resistance shifts the dose-response curve.
The projection models each dose step as an exponential approach toward a dose-specific target. At each dose transition, the trajectory is continuous: the value you have reached becomes the starting point for the next segment's approach to a deeper target. This produces the staircase-like acceleration pattern seen in clinical trial data when patients titrate to higher doses.
References
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. (STEP 1)
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. (SURMOUNT-1)
Aronne LJ, Sattar N, Horn DB, et al. Continued treatment with tirzepatide for maintenance of weight reduction in adults with obesity. JAMA. 2024;331(1):38-48. (SURMOUNT-4)
Lingvay I, Brown-Frandsen K, Colhoun HM, et al. Semaglutide for cardiovascular event reduction in people with overweight or obesity: SELECT trial. N Engl J Med. 2023;389(24):2221-2232.