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GLP-1 Drug Index
One number per medication: how much weight it takes off for each unit of side effects it causes. Higher is better. Built only from each drug's main Phase 3 trial.
Weight loss bars are coloured by medication. Side-effect burden: lower is better. Not sure which fits you? Take the quiz →
The numbers behind the index
| Medication | Weight loss | Nausea | Vomiting | Diarrhea | Constipation | Quit (side effects) | Stomach score | Burden | Index |
|---|---|---|---|---|---|---|---|---|---|
| TirzepatideSURMOUNT-1, n=2,539 | 22.5% | 31.0% | 12.2% | 23.0% | 11.7% | 6.2% | 19.5 | 25.7 | 8.8 |
| RetatrutideTRIUMPH-1, n=2,339 | 28.3% | 42.4% | 25.3% | 32.0% | 26.1% | 11.3% | 31.5 | 42.8 | 6.6 |
| Semaglutide pill*OASIS 4, n=307 | 16.6% | 46.6% | 30.9% | 17.6% | 20.1% | 6.9% | 28.8 | 35.7 | 4.6 |
| SemaglutideSTEP 1, n=1,961 | 16.9% | 44.2% | 24.8% | 31.5% | 23.4% | 7.0% | 31.0 | 38.0 | 4.5 |
| OrforglipronATTAIN-1, n=3,127 | 12.4% | 33.7% | 24.0% | 23.1% | 25.4% | 10.3% | 26.6 | 36.9 | 3.4 |
Methodology
Formula. Stomach score = average of the nausea, vomiting, diarrhea and constipation rates. Side-effect burden = stomach score + quit rate (the share of people who stopped because of side effects, counted once). Index = average weight loss ÷ burden × 10.
Why quitting counts once. Because the stomach score averages four symptoms, one point of quit rate already weighs as much as four people each having one symptom. Most people who quit also had stomach side effects that are already counted, so a higher weight would count them twice. With a weight of 0, 2 or 3 the order of the drugs stays the same.
Data. Highest dose in each drug's main Phase 3 obesity trial in adults without diabetes: SURMOUNT-1 (tirzepatide), STEP 1 (semaglutide), OASIS 4 (Wegovy pill), ATTAIN-1 (Foundayo) and TRIUMPH-1 (retatrutide). Weight loss uses the result for people who kept taking the medication where reported. Rates are raw, not placebo-adjusted.
Limitations. The trials are separate, of different lengths (64 to 80 weeks) and populations, so this is not a head-to-head comparison. Severity is not captured: a mild and a severe episode count the same. Other benefits, such as semaglutide's proven heart protection, and other side effects, such as retatrutide's skin-sensation changes (12.5%), are not part of the score.
* Small trial. The Wegovy pill's figures come from OASIS 4, which enrolled 307 adults (about 205 on the pill). Its side-effect rates are less precise than those of trials with thousands of people, so treat its position against the Wegovy injection as approximate.
The index ranks medications on trial averages. It is not a recommendation for any individual; only a clinician who knows your health can help you choose.