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GLP-1 Weight Loss Calculator

Get a personalized weight loss projection for semaglutide or tirzepatide, based on average results from phase 3 clinical trials.

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How We Calculate GLP-1 Weight Loss

This calculator uses average monthly weight loss rates from published clinical trials: the STEP 1–5 trials for semaglutide and the SURMOUNT-1 trial for tirzepatide. Rates are capped at the maximum percentage loss observed in trials to prevent unrealistic projections.

Semaglutide vs Tirzepatide: Expected Weight Loss

Semaglutide (Ozempic 1 mg for diabetes, Wegovy 2.4 mg for obesity) produced an average 14.9% body weight reduction over 68 weeks in the STEP 1 trial (Wilding et al., NEJM, 2021). Tirzepatide produced up to 20.9% reduction over 72 weeks in SURMOUNT-1 (Jastreboff et al., NEJM, 2022).

Factors That Affect Your Results

  • Starting weight — higher starting weight often produces larger absolute losses
  • Diet and caloric deficit during treatment
  • Exercise habits
  • Dose titration schedule and tolerability
  • Duration of treatment

Frequently Asked Questions

How accurate is this GLP-1 weight loss calculator?↓
The calculator uses average weight loss rates from phase 3 clinical trials (STEP, SURMOUNT). Real results vary based on adherence, diet, exercise, and individual metabolism. Treat projections as a guideline, not a guarantee.
How much weight can you lose on semaglutide in 3 months?↓
Clinical trials show an average of ~5–7% body weight loss in 12–16 weeks on semaglutide. For someone starting at 220 lbs, that's roughly 11–15 lbs in 3 months.
Is tirzepatide better than semaglutide for weight loss?↓
Tirzepatide (Mounjaro/Zepbound) shows ~21% body weight loss in trials versus ~15% for semaglutide. However, both are effective; your provider can help choose based on your health profile.
What is the maximum weight loss on GLP-1 medications?↓
Most people lose 15–21% of starting body weight at maximum efficacy. Losses plateau after 12–18 months. Discontinuing medication typically results in weight regain.
Do I need to diet while on GLP-1 medications?↓
GLP-1 medications work best alongside a calorie deficit. They suppress appetite, making it easier to eat less — but they don't replace a healthy diet and exercise.

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