Averages, not predictionsThese are group averages from a clinical trial with diet and activity counseling. Individual results varied widely. The tables convert averages into pounds and kilograms for illustration only.
SURMOUNT-1 at a glance
2,539 adults with a BMI of 30 or more, or 27 or more with a weight-related condition, and without diabetes, were randomized to tirzepatide 5, 10 or 15 mg or placebo for 72 weeks, including up to 20 weeks of dose escalation.[1][2]
- −3.1%Placebo: average weight change at 72 weeks
- −15%5 mg: average weight change at 72 weeks
- −19.5%10 mg: average weight change at 72 weeks
- −20.9%15 mg: average weight change at 72 weeks
| Placebo | 5 mg | 10 mg | 15 mg | |
|---|---|---|---|---|
| Average weight change (treatment-regimen) | −3.1% | −15% | −19.5% | −20.9% |
| Average weight change (efficacy estimand) | −2.4% | −16% | −21.4% | −22.5% |
| Lost ≥5% of body weight | 35% | 85% | 89% | 91% |
| Lost ≥10% | 18.8% | 68.5% | 78.1% | 83.5% |
| Lost ≥15% | 8.8% | 48% | 66.6% | 70.6% |
| Lost ≥20% | 3.1% | 30% | 50.1% | 56.7% |
The treatment-regimen figures count everyone who was randomized, whether or not they kept taking the drug; they appear in the NEJM paper and the FDA label.[1][2] The efficacy-estimand figures count people while they stayed on treatment, so they are larger; Lilly's press release led with those.[3] The ≥10/15/20% shares are the label's figures.[2]
How long does it take for Zepbound to work?
Zepbound starts working within weeks: in SURMOUNT-1, 82% of people taking their doses had lost at least 5% of body weight by week 12, and the average loss on 10 or 15 mg was 13.2 kg by week 20.[8][7]
| Time | What happens | Source |
|---|---|---|
| 24 hours | Blood level peaks after each weekly injection (range 8 to 72 hours) | Label[2] |
| 4 weeks | Steady blood levels reached on a constant weekly dose | Label[2] |
| Week 12 | 82% of people with at least 75% of doses had lost ≥5% of body weight | Post hoc analysis[8] |
| Week 20 | End of escalation to 15 mg; average −13.2 kg on 10 or 15 mg vs −2.5 kg on placebo | ClinicalTrials.gov results[7] |
| Week 24 | 70% of the slower responders had reached ≥5% | Post hoc analysis[8] |
| Week 72 | Average −15% to −20.9% by dose; 90% of slower responders reached ≥5% | NEJM, post hoc[1][8] |
Weight kept falling for most of the 72 weeks, so the early figures are a fraction of the final result. The 18% who had not reached 5% by week 12 took 24.8 weeks on average to get there.[8] The week-20 figure counts people while they stayed on treatment.[7]
What dose of Zepbound is most effective?
15 mg produced the largest average weight loss in SURMOUNT-1, but the gap above 10 mg was small: −20.9% versus −19.5%, while 5 mg gave −15%.[1]
| Dose | Average change | Reached ≥5% | Reached ≥20% | Stopped for side effects |
|---|---|---|---|---|
| 5 mg | −15% | 85% | 30% | 4.3% |
| 10 mg | −19.5% | 89% | 50.1% | 7.1% |
| 15 mg | −20.9% | 91% | 56.7% | 6.2% |
Higher doses also brought more vomiting and diarrhea, so the label leaves the maintenance dose to the prescriber, based on “treatment response and tolerability.”[2] For sleep apnea, only 10 and 15 mg are maintenance doses.[2]
Not losing weight on Zepbound?
Most people in the trial lost weight, but not everyone: 85–91% of people on 5–15 mg lost at least 5% of body weight by week 72, so roughly 1 in 10 did not.[1] The averages also hide wide individual variation. The label does not give a cut-off for stopping; it asks prescribers to weigh response and tolerability when choosing the dose, and moving up a step is possible after at least 4 weeks.[2] See the tirzepatide dosage chart.
Zepbound weight loss in pounds and kilograms
Average percentage change (treatment-regimen) applied to example starting weights. Simple multiplication, not a forecast for any person.
| Starting weight | Placebo | 5 mg | 10 mg | 15 mg |
|---|---|---|---|---|
| 180 lb | -5.6 lb | -27 lb | -35.1 lb | -37.6 lb |
| 200 lb | -6.2 lb | -30 lb | -39 lb | -41.8 lb |
| 220 lb | -6.8 lb | -33 lb | -42.9 lb | -46 lb |
| 250 lb | -7.7 lb | -37.5 lb | -48.7 lb | -52.2 lb |
| 280 lb | -8.7 lb | -42 lb | -54.6 lb | -58.5 lb |
| 300 lb | -9.3 lb | -45 lb | -58.5 lb | -62.7 lb |
| Starting weight | Placebo | 5 mg | 10 mg | 15 mg |
|---|---|---|---|---|
| 80 kg | -2.5 kg | -12 kg | -15.6 kg | -16.7 kg |
| 90 kg | -2.8 kg | -13.5 kg | -17.5 kg | -18.8 kg |
| 100 kg | -3.1 kg | -15 kg | -19.5 kg | -20.9 kg |
| 110 kg | -3.4 kg | -16.5 kg | -21.4 kg | -23 kg |
| 120 kg | -3.7 kg | -18 kg | -23.4 kg | -25.1 kg |
| 140 kg | -4.3 kg | -21 kg | -27.3 kg | -29.3 kg |
When the FDA approved Zepbound, it summarized the result as people on 15 mg losing “on average 18% of their body weight compared to those randomized to placebo”, which is the difference between the two groups.[6]
In people with type 2 diabetes (SURMOUNT-2)
Weight loss was smaller in adults with obesity and type 2 diabetes: −12.8% on 10 mg and −14.7% on 15 mg vs −3.2% on placebo at 72 weeks.[5][2]
What happens when you stop taking Zepbound (SURMOUNT-4)
Everyone first took tirzepatide for 36 weeks, reaching their maximum tolerated dose (10 or 15 mg) and losing −20.9% on average. Then 670 people were randomized to keep taking it or switch to placebo for another 52 weeks.[4]
| Outcome | Continued tirzepatide | Switched to placebo |
|---|---|---|
| Weight change, week 36 to 88 | −5.5% | +14.0% |
| Total change, week 0 to 88 | −25.3% | −9.9% |
| Kept at least 80% of the earlier loss | 89.5% | 16.6% |
The authors concluded that “withdrawing tirzepatide led to substantial regain of lost weight.”[4]
Related
- Side effects by doseThe other side of the same trials
- Sleep apnea resultsSURMOUNT-OSA
- Tirzepatide vs semaglutideThe head-to-head trial
Frequently asked questions
How much weight do you lose on tirzepatide 5 mg?
In SURMOUNT-1 the average was −15% after 72 weeks on 5 mg, vs −3.1% on placebo (treatment-regimen estimand).[1]
How long does it take for Zepbound to work?
Is 15 mg much better than 10 mg?
Do you regain weight after stopping tirzepatide?
In SURMOUNT-4, people switched to placebo regained an average of 14% of body weight over the next year, while those who continued lost a further 5.5%.[4]
Sources
- Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1)
- Zepbound (tirzepatide) injection: prescribing information, Medication Guide and Instructions for Use
- Lilly's SURMOUNT-1 results published in NEJM (efficacy estimand)
- Aronne LJ et al. Continued treatment with tirzepatide for maintenance of weight reduction (SURMOUNT-4)
- Garvey WT et al. Tirzepatide once weekly for obesity in type 2 diabetes (SURMOUNT-2)
- FDA approves new medication for chronic weight management
- NCT04184622 (SURMOUNT-1) posted results: outcome measures and adverse events
- Ard J et al. Weight reduction over time in tirzepatide-treated participants by early weight loss response: post hoc analysis in SURMOUNT-1