You started treatment, the scales moved steadily for weeks or months, and now they’ve stopped.
If you’ve hit a weight loss plateau on Mounjaro or Wegovy, you’re far from alone, and it doesn’t mean your medication has stopped working.
In fact, clinical trial data shows that slowing down is an expected part of almost every medical weight loss journey.
Below, our pharmacy team explains why plateaus happen, how to tell a true plateau from a normal fluctuation, and the practical steps that can help you get moving again.
What is a weight loss plateau?
A weight loss plateau is a period when your weight stays roughly the same for several weeks, even though you’re sticking to your treatment and routine.
It’s different from day-to-day fluctuations. Your weight can easily vary by 1–2kg between mornings because of fluid, salt, hormones, digestion and what you ate the night before.
As a rule of thumb, if your weight hasn’t changed meaningfully for three to four weeks, you may be on a plateau.
If it’s only been a week or two, it’s usually too early to tell.
Weighing yourself at the same time of day, under the same conditions, and focusing on the weekly trend rather than single readings will give you a much clearer picture.
Why plateaus happen on weight loss injections
Your body adapts to a smaller you
As you lose weight, your body needs less energy.
A smaller body burns fewer calories at rest and on the move, so the calorie deficit that worked at the start of treatment gradually shrinks.
On top of this, the body becomes more energy-efficient during weight loss, a process known as metabolic adaptation, which can slow progress further.
Plateaus are part of the clinical evidence
A plateau isn’t a sign that something has gone wrong. It’s what the research predicts.
A 2025 analysis of SURMOUNT-1, the main trial of tirzepatide (Mounjaro) for weight management, found that roughly nine in ten participants who responded to treatment had reached a weight plateau by week 72.
The typical time to plateau was between around 24 and 36 weeks, depending on starting BMI.
Semaglutide (Wegovy) follows a similar pattern.
In the STEP 1 trial, people lost an average of 14.9% of their body weight over 68 weeks, with most of that loss happening in the first year before the curve levelled off. Put simply, these medicines help your body settle at a new, lower weight.
They’re not designed to cause weight loss indefinitely.
Habits can drift over time
Early on, reduced appetite does a lot of the heavy lifting.
Months in, it’s common for portion sizes to creep back up, for liquid calories such as alcohol, juices and coffee-shop drinks to return, or for activity levels to dip.
None of this means you’ve failed. It simply means your routine is due a fresh look.
You may still be titrating
Mounjaro and Wegovy are started at a low dose and increased gradually, usually every four weeks, to help your body adjust.
If you’re still on a lower dose, slower progress is normal. Late or missed doses can also reduce the effect. Read more in our guide to titration and how it works.
Plateau or just a slow few weeks? Signs to check
Before deciding you’ve stalled, ask yourself:
- Are your clothes fitting differently? A tape measure around your waist can reveal progress the scales miss, especially if you’ve started strength training.
- Has anything changed recently? A dose increase, your menstrual cycle, a salty meal or illness can all cause temporary water retention.
- Has your appetite returned? This is useful information to share with your prescriber at your next review.
6 practical ways to move past a plateau
- Review what you’re eating. Keep a simple food diary for one week. Many people are surprised by how much snacks, sauces and drinks add up.
- Prioritise protein. Including protein at every meal helps you stay full and protects muscle. See our guide to prioritising protein while using weight loss medication.
- Add strength training. Muscle supports your metabolism. Two sessions of resistance exercise a week, alongside regular walking, is a realistic target. Our article on how many steps to lose weight can help you set a daily goal.
- Go easy on alcohol. It adds calories, weakens resolve around food and can make side effects such as nausea worse.
- Protect your sleep and manage stress. Poor sleep is linked to increased hunger and cravings, making it harder to stick to your plan.
- Take your dose on time. Inject on the same day each week and set a reminder so doses aren’t missed.
Just as important is what not to do.
Avoid crash dieting or skipping meals, which can backfire and lead to muscle loss.
Never increase your dose yourself or buy extra pens from unregulated sellers.
Only your prescriber can safely adjust your treatment, and black market weight loss medication carries serious risks.
When to speak to your prescriber
Get in touch with our pharmacy team if:
- your weight has barely changed for six to eight weeks or more, despite following your plan
- you’re unsure whether you’re on the right dose
- side effects are stopping you from eating well or taking your doses
- you’ve started a new medicine or been diagnosed with a new condition, as some medicines and conditions, such as an underactive thyroid, can affect weight
NICE guidance for tirzepatide recommends that treatment is reviewed if less than 5% of starting weight has been lost after six months on the highest tolerated dose.
Our prescribers take a similar, individual approach. If your progress has stalled, we’ll review your dose, your routine and whether your current treatment is still the right fit for you.
The bottom line
A weight loss plateau is a normal, expected stage of treatment and often a sign that your body is adjusting to a healthier weight.
Small, consistent changes to your eating, activity and routine can help restart progress, and maintaining the weight you’ve already lost is a real achievement in itself.
Need support? If you’re already an Onlinemeds patient, message our pharmacy team for a treatment review. New to medical weight loss? Start your online consultation today.
Frequently asked questions
How long does a weight loss plateau last on Mounjaro?
It varies from person to person. Short stalls of a few weeks are common and often pass on their own. If your weight hasn’t moved for six to eight weeks, it’s worth speaking to your prescriber.
Should I increase my dose if I hit a plateau?
Only on the advice of your prescriber. A higher dose isn’t always the answer, and dose changes need to account for side effects, your medical history and how long you’ve been on treatment.
Does a plateau mean my medication has stopped working?
Not usually. The medication is still helping to control your appetite, which supports you in maintaining the weight you’ve lost. A plateau typically reflects your body adapting, not the treatment failing.
This article is for general information only and isn’t a substitute for personal medical advice. Always follow the guidance of your prescriber and the patient information leaflet supplied with your medicine.
Sources
- Horn DB et al. (2025). Time to weight plateau with tirzepatide treatment in the SURMOUNT-1 and SURMOUNT-4 clinical trials. Clinical Obesity. doi:10.1111/cob.12734
- Wilding JPH et al. (2021). Once-weekly semaglutide in adults with overweight or obesity (STEP 1). New England Journal of Medicine, 384:989–1002.
- NICE TA1026: Tirzepatide for managing overweight and obesity