Not Losing Weight in Week 2 on Mounjaro? What's Normal (October 2026)

01 · The short answer

Is it normal to lose nothing in the second week?

Yes, it is normal. The 2.5mg starting weeks are about adjustment, and experiences differ widely: some people notice appetite change and early loss in week one, others feel little until a higher dose, and both are normal.¹³ If your friend lost quickly and you did not, that says very little about how you will do over the coming months.

Mounjaro is the brand name for tirzepatide, a once-weekly injection licensed in the UK for weight management in adults.¹ It works by activating two gut-hormone receptors, GIP and GLP-1, which help regulate appetite and slow how quickly the stomach empties.¹ In the first weeks that effect is still being introduced gently, which is deliberate. The aim is to let your body settle before the dose rises.

Weight loss on Mounjaro is gradual by design. The first weeks on 2.5mg are an adjustment phase and losses are usually modest; most measurable progress builds from 5mg onward, month by month.⁴ Think in months, not days.

02 · Your next step

What should you do if the scale is still flat?

Keep injecting on schedule, keep logging food and weight, and wait for your prescriber's planned review. Do not change your dose yourself. Do not skip, double or add extra injections, and do not add unlicensed products. If a symptom worries you, speak to your prescriber or pharmacist.

Three practical checks are worth doing now. First, weigh at the same time of day, no more than once or twice a week. Second, note appetite rather than just weight: are you feeling full sooner and less hungry between meals? Third, record your waist and how clothes fit, because the scale is only one signal.

If you are already a customer, our prescribing team carries out ongoing monthly reviews and handles dose titration. If you are still comparing options, the Mounjaro pen starts at £169.99 for the 2.5mg pen at standard price, and our weight loss clinic explains how a free consultation reviewed by a GPhC-registered prescriber works.

03 · Why the scale stalls

Why the scale may not move in the second week

The most common reason is simply timing. You are very early in treatment, still on the starting dose, and the full appetite effect has not been reached yet. The starting weeks are an adjustment phase, and some people feel little until a higher dose.¹³

A second reason is water. Early loss includes water weight, so the trend over weeks matters more than any single weigh-in.¹³ Salt, hormones, a harder workout, constipation or a larger meal the night before can all shift the number on the scale without any change in body fat. A flat reading on one morning is often noise.

A third reason is the injection cycle. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹³ If your appetite is only quieter for part of the week, you may find the later days harder, and eating can creep up. That pattern is worth noticing and writing down.

A fourth reason is eating habits that are easy to miss. Mounjaro supports a reduced-calorie diet; it does not replace one.² Liquid calories, snacking while cooking, larger portions of the foods you still enjoy and weekend meals can all absorb the benefit of a reduced appetite. This is not a criticism. It is the first place to look.

Finally, individual variation is wide. Two people on the same dose can have different appetite responses. A slow start does not predict a slow finish, and the dose you respond to may still be ahead of you.

04 · Week-by-week expectations

What to expect in the second week and beyond

In the second week you should expect modest changes at most. Some people notice that food noise is quieter, portions feel larger than they can finish, or they feel full sooner. Others notice almost nothing yet. Both are within the normal range.

Common early effects include mild nausea, altered appetite and tiredness in the first days after each injection, and these usually settle.¹³ Side effects are listed in the patient information leaflet, which is worth reading in full. If something feels severe, persistent or unexpected, tell your prescriber, and you can report suspected side effects through the Yellow Card scheme. For severe, persistent stomach pain, get medical help straight away.¹⁹

Looking further ahead, three months in, most people are still on the lower rungs of the dose ladder, so trial-average losses at this stage are modest compared with the headline figures.² A sensible expectation on a standard titration is mid single digits as a percentage of body weight, with wide individual variation.²

The headline trial figures take far longer. In the SURMOUNT-1 trial of 2,539 adults, people taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.² These are trial averages and individual results vary. They show the scale of the journey, not a second-week target.

If you want to compare notes with what others experience at this stage, our Mounjaro week 2 guide goes through it in more detail.

05 · How much to expect

How much weight should you lose in the first couple of weeks?

What the evidence supports is a gradual pattern: losses are usually modest on the starting dose, and most measurable progress builds from 5mg onward.⁴

That is why prescribers talk about trend rather than targets this early. Trials measured results at 72 weeks, so any short-term number you see quoted online should be treated with caution. If someone promises dramatic weight-loss claims in a fortnight, that is marketing, not medicine.

A more useful approach is to set process goals for the first month: inject on the same day each week, eat protein at every meal, stay active in a way you can sustain, sleep properly and keep alcohol low. Then review the trend at your prescriber check-in.

There is a formal review point built in. If you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, your prescriber will discuss whether continuing or stopping is right for you.⁴ That is the point at which a lack of response is judged, not the second week.

If you are further along and still stuck, our guide for people who say I'm on Mounjaro and not losing weight covers the later stages, and the page on not losing any weight on Mounjaro covers the case where nothing at all has changed.

06 · Is it working?

What are the signs Mounjaro is working, or not?

The first sign is usually appetite, not the scale. Most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹ If you notice smaller portions satisfying you, fewer cravings or less thinking about food, the medicine is doing something even if the number has not changed.

Other signals matter too. In trials, weight loss on tirzepatide came with average improvements in waist size, blood pressure, cholesterol and blood-sugar measures.² These are trial-average secondary outcomes, not promises, but they explain why a tape measure and a blood-pressure check can show progress before the scale does.

Signs it may not be working yet are equally plain. Your appetite feels unchanged, you are eating as much as before and the trend is flat over several weeks. In the second week that is not alarming. It becomes a question for your prescriber once you have been on treatment longer, particularly if you are on a higher dose with no appetite change.

Signs it needs a conversation sooner are different. Severe or persistent vomiting should be raised with your prescriber promptly rather than waited out; if you cannot keep fluids down, contact your clinical team, as dehydration needs medical help straight away. For severe, persistent stomach pain, get medical help straight away.

The question of whether fat is leaving your body cannot be answered by the scale alone. Clothes fit, waist measurements, energy, blood pressure and blood-sugar readings from your own clinician are all better evidence than a single weigh-in.

07 · Plateaus and stalls

Stuck at the same weight: plateaus and what to check

Weight loss on Mounjaro is not linear. Plateaus of a few weeks are normal and expected as the body adapts to a lower weight.¹³ In the second week, being stuck usually means you are simply early, but the same checklist applies later on.

Within the licence, the responses are to review food intake honestly, because portions drift back up; protect protein and activity; check the basics such as sleep and alcohol; and discuss with your prescriber whether a dose step-up is appropriate if you are not yet at maximum.¹³ A plateau is not a reason to double doses or add unlicensed products.¹³

It helps to treat the checklist as a practical routine:

• Write down everything you eat and drink for a few days, including drinks and snacks.
• Check protein at each meal, because a smaller appetite can make it easy to under-eat protein.
• Look at sleep, stress and alcohol, which all influence appetite and choices.
• Keep moving in a way you enjoy, since activity is part of the plan alongside the medicine.
• Tell your prescriber about side effects that make it hard to eat well, such as nausea or constipation.

If you are asking why you are not losing weight even though you are taking 5mg, that is a different stage with a different answer. Read our guides on not losing weight on 5mg Mounjaro and expert tips for 5mg. Those pages cover what changes once you have stepped up.

08 · Water, fat and skin

Water weight, drinking water and "jiggly" fat

Early scale changes include water weight.¹³ That is why a big drop one week and nothing the next is common, and why a flat reading does not prove fat loss has stalled. Weigh consistently and look at the direction over weeks.

Does drinking water help you burn fat? Staying hydrated is sensible, especially if you have nausea or constipation, and drinking water can help with feeling comfortable, but treat it as a good habit rather than a lever for weight loss.

How long does fat stay "jiggly" before it goes? It is not a measure of how well treatment is working. Body shape changes at different rates for different people. Protecting protein intake and staying active alongside treatment are the practical steps within the plan, and your prescriber can discuss body-composition concerns with you.

For people who are still in the earliest days, our week 1 guide covers the first injection and what to expect before this stage. The core message is the same: be patient, be consistent, and judge the trend.

09 · Serious side effects

Serious side effects: when to get help straight away

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for: severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹

10 · When to speak up

When to speak to your prescriber

You do not need to wait for a formal review if something concerns you. Contact your prescriber if side effects are stopping you eating or drinking properly, if you are unsure about your dose or injection technique, or if you are taking other medicines such as insulin or sulfonylureas, where doses may need adjusting because of the risk of low blood sugar.

Treatment response is reviewed by your prescriber. If you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, your prescriber will discuss whether continuing or stopping is right for you.⁴ Until then, the right question is not "why has nothing happened yet?" but "is the trend heading the right way over months?"

Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity, and individual results vary.¹ This page is information, not a substitute for medical advice.

If you want to track your progress properly, GLPTrackr is our free companion app for tracking a GLP-1 journey on iOS and Android. Our team can be reached Monday to Friday, 9am to 5pm, by email at support@everydaymeds.co.uk, through the account portal chat or by phone on 0333 207 0413. Ongoing monthly reviews, dose titration and side-effect support come with treatment.

If you are weighing up whether treatment is right for you in the first place, NHS access to Mounjaro is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the primary-care rollout began in June 2025 with the highest-need groups first.⁴ Many people who meet the licensed criteria choose regulated private treatment rather than waiting.