Tirzepatide Timeline: Week by Week, What Changes and When
SURMOUNT-1 ran 72 weeks. By the end, people on tirzepatide 15 mg weekly had lost 20.9% of their body weight on average, against 3.1% on placebo. Side effects are most common in the first weeks and after each dose increase.
- Average loss, top dose
- 20.9%
- On placebo
- 3.1%
- Trial length
- 72 weeks
- Trial
- SURMOUNT-1
Zepbound in brief
The half-life is 5 to 6 days: after 5.5 d, half is gone, and five half-lives (27.5 d) leave about 3% behind.
In SURMOUNT-1 over 72 weeks, weight loss was 20.9% of body weight, compared with 3.1% on placebo.
The maker's price page gives each monthly figure in US dollars, including list price and self-pay offers.
Sources: FDA label (DailyMed), Eli Lilly 1 2, cnbc.com.
Tirzepatide timeline: the numbers first
| Trial | Dose group | Average weight lost | Placebo or comparison | Weeks | Who was in it |
|---|---|---|---|---|---|
| SURMOUNT-1 | Tirzepatide 5 mg weekly | 15% | 3.1% | 72 | Adults with obesity or overweight, without diabetes |
| SURMOUNT-1 | Tirzepatide 10 mg weekly | 19.5% | 3.1% | 72 | Adults with obesity or overweight, without diabetes |
| SURMOUNT-1 | Tirzepatide 15 mg weekly | 20.9% | 3.1% | 72 | Adults with obesity or overweight, without diabetes |
| SURMOUNT-2 | Tirzepatide 10 mg weekly | 12.8% | 3.2% | 72 | Adults with type 2 diabetes who also have obesity or overweight |
| SURMOUNT-2 | Tirzepatide 15 mg weekly | 14.7% | 3.2% | 72 | Adults with type 2 diabetes who also have obesity or overweight |
| SURMOUNT-5 | Tirzepatide 10 or 15 mg weekly (Zepbound) | 20.2% | semaglutide (Wegovy) | 72 | Adults with obesity, without type 2 diabetes |
Sources: SURMOUNT-1 (FDA label (DailyMed)), SURMOUNT-2 (PubMed), SURMOUNT-5 (PubMed)
What the average comes to in pounds
The trial reported an average of 20.9%, which was applied to three starting weights. This calculation is arithmetic, not a prediction for one person: some lose more, while others lose less.
| Starting weight | Average loss on tirzepatide 15 mg weekly | Average loss on placebo |
|---|---|---|
| 180 lb | about 38 lb | about 6 lb |
| 220 lb | about 46 lb | about 7 lb |
| 260 lb | about 54 lb | about 8 lb |
Sources: FDA label (DailyMed).
Week by week
- The first weeks are when stomach side effects show up most often, as the dose is low and going up. After each dose increase, these effects often come back for a few days at a time.
- Week 72: SURMOUNT-1 finishes here, and the average loss listed above comes from that point.
Sources: health.clevelandclinic.org and the FDA label (DailyMed).