How much weight do you lose on Mounjaro each week?
About 0.5% of your weight a week, on average, over the first months. But about 1 in 10 on Mounjaro lose under 5% in total. One check at 6 months shows if that’s you.
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What is the average weekly weight loss on Mounjaro?
About 0.5% to 0.6% of your starting weight a week, over the first months. If you start at 100 kg, that’s about half a kilo a week.
In one trial, people who stayed on Mounjaro for 36 weeks lost 20.9% on average. That works out at about 0.6% a week. On Wegovy, people lost 10.6% in 20 weeks, or about 0.5% a week.
| Week | Average lost | If you started at 100 kg |
|---|---|---|
| Week 20 on Wegovy | 10.6% | About 10.6 kg |
| Week 36 on Mounjaro (10 or 15 mg) | 20.9% | About 20.9 kg |
| Week 68 on Wegovy | 14.9% | About 14.9 kg |
| Week 88 on Mounjaro, still taking it | 25.3% | About 25.3 kg |
Sources: STEP 4; SURMOUNT-4; STEP 1
Week 68 counts everyone who started, even those who stopped. The other rows count only people who stayed on it.
The pace isn’t steady. After week 36, people who kept taking Mounjaro lost 5.5% more over the next 52 weeks. So most of the loss came in the first 8 to 9 months, then it slowed.
Weigh yourself once a week, then turn the change into a percentage with the weight loss percentage calculator.
What is the average weight loss on Mounjaro and Wegovy?
Over 68 to 72 weeks, about 16 months, Mounjaro averaged 15% to 21%, depending on the dose. Wegovy averaged about 15%.
| Medicine and dose | Average lost | Lost 5% or more |
|---|---|---|
| Mounjaro 5 mg | 15.0% | 85% |
| Mounjaro 10 mg | 19.5% | 89% |
| Mounjaro 15 mg | 20.9% | 91% |
| Wegovy 2.4 mg | 14.9% | 86% |
| Dummy injection (placebo) | 2.4% to 3.1% | 32% to 35% |
Sources: SURMOUNT-1; STEP 1
Head to head, in one 72-week trial, Mounjaro averaged 20.2% and Wegovy 13.7%. Each person took the highest dose they could manage.
The NHS says these medicines work when combined with exercise and changes to your diet. The medicine alone isn’t the whole plan.
Source: SURMOUNT-4
The trial found that stopping led to substantial regain. Wegovy looked similar: after a switch to a dummy injection at week 20, weight went back up 6.9% by week 68.
So ask your prescriber early what the long-term plan is.
How much weight do you lose in the first month?
Month one is the starter dose. Mounjaro starts at 2.5 mg a week for 4 weeks, then goes up to 5 mg.
How the Mounjaro dose climbs
- 1
Weeks 1 to 4
2.5 mg a week, the starting dose.
- 2
Week 5
Up to 5 mg a week.
- 3
Every 4 weeks or more
Up in 2.5 mg steps, if needed.
- 4
Top dose
15 mg a week is the most.
Source: Mounjaro SmPC
Wegovy starts at 0.25 mg and climbs over 16 weeks to 2.4 mg. The slow climb is there to cut the chance of stomach side effects.
In the main Mounjaro trial, the dose took 20 weeks to climb. Side effects like feeling sick came mostly during that climb. So the averages above come after months on higher doses.
Don’t judge it on month one. Write down your weight on day one, so you have a fair starting point.
Why am I not losing weight on Mounjaro?
In trials, 9% to 15% of people on Mounjaro and about 14% on Wegovy lost under 5% in total.
That check is NICE’s 5% rule. If you’ve lost less than 5% after 6 months on the highest dose you can manage, you and your prescriber decide whether to carry on. For Wegovy, NICE says to consider stopping below 5% after 6 months.
- Below 5 %Under 5%. NICE: decide whether to carry on.
- 5 to just under 10 %Past NICE’s 5% check.
- 10 % or above10% or more. Wegovy users averaged 10.6% by week 20.
Sources: NICE TA1026; NICE TA875; STEP 4
Before 6 months, check the simple things:
- You may still be on a low dose. It goes up in steps.
- Missed doses. On Mounjaro, a dose more than 4 days late is skipped. On Wegovy, it’s more than 5 days.
Never stop or change a prescribed medicine without your prescriber. Take your weekly weights to them and talk it through.
How to make each week count
Six things to do each week on Mounjaro or Wegovy
- Inject on the same day each week, in your thigh, tummy or upper arm, and change the spot each time.
- Weigh yourself once a week, on the same day and at the same time.
- Eat a healthy, balanced diet and build in exercise.
- Avoid alcohol where you can, as it can make feeling or being sick worse.
- On Mounjaro, use extra barrier contraception, such as condoms, a diaphragm or a cap, for 4 weeks after starting and for 4 weeks after each dose increase.
- Get your medicine only from a registered pharmacy.
Sources: NHS: tirzepatide; NHS: semaglutide
On Wegovy, the NHS says to use contraception if there’s a chance you could get pregnant.
Want to keep your muscle as the weight comes off? See how to keep muscle while losing weight and nutrients to watch on weight loss injections like Mounjaro and Wegovy.
For checks along the way, see blood tests on Mounjaro and blood tests on Wegovy.
When to speak to a GP
Talk to your GP or prescriber if:
- You’ve lost less than 5% after 6 months on the highest dose you can manage.
- Side effects bother you or don’t go away. A pharmacist can help too.
- You want to get pregnant. The NHS says to stop Mounjaro at least 4 weeks before you start trying.
- Call 111 if you have severe pain in your stomach or back that doesn’t go away, or severe tummy pain. These can be signs of an inflamed pancreas or gallstones.
- Call 111 if you think you’re having any other serious side effect, such as sudden loss of vision on Wegovy, or you’ve used more than your dose.
Call 999 if you think you’re having a severe allergic reaction. Signs include your lips, mouth, throat or tongue suddenly swelling, struggling to breathe or swallow, wheezing, or suddenly feeling confused or dizzy, or fainting.