Ozempic and Mounjaro reviews: what studies show and what we see in consultations

Which side effects come up most often in trials?

Digestive side effects are by far the most common. Across three trials of semaglutide at the Wegovy dose, 72.9% of people experienced at least one, compared with 47.1% on placebo [1]. Almost all were mild or moderate [1].

Nausea affected 43.9%, with episodes lasting a median of 8 days. Diarrhoea affected 29.7%, with episodes lasting 3 days. Vomiting affected 24.5%, with a median duration of 2 days [3]. Constipation affected 24.2%, but episodes lasted much longer, with a median duration of 47 days [3].

With tirzepatide (Mounjaro), the pattern is similar in weight-management trials. At the 15 mg dose, some form of digestive disorder occurred in 59.2%, compared with 30.3% on placebo [2]. Nausea affected 31.0% and diarrhoea 23.0% [2]. Most cases were mild or moderate [2].

The Ozempic and Mounjaro pages give details of each finding. Differences in indication and formulation are covered in the comparison of Ozempic, Wegovy and Mounjaro.

Do the nausea symptoms go away over time?

They ease, although they do not disappear completely. A pooled analysis of three semaglutide trials found that nausea, diarrhoea and vomiting peaked at around week 20, shortly after participants reached the full dose [1]. They then declined [1].

The same analysis adds a detail that is rarely mentioned. All four digestive symptoms remained more common than with placebo throughout the 68-week study [1]. And weight loss depended very little on them: digestive symptoms accounted for less than one point of the difference compared with placebo [1].

Feeling unwell with nausea does not make the treatment work better.

Constipation is the symptom that lasts longest [3]. If you are finding it difficult to open your bowels, it is the first thing we work on in consultations, with fibre, water and movement.

How many people stop treatment, and why?

In trials, permanent discontinuation due to digestive side effects was uncommon: 4.3% with semaglutide [3] and between 1.9% and 4.4% with tirzepatide, depending on the dose [2].

Outside trials, stopping is much more common. In a US cohort of more than 125,000 adults, 46.5% of those with type 2 diabetes and 64.8% of those without it had stopped by one year [4]. The first course of treatment lasted a median of 176 days, around six months [4].

Having moderate or severe digestive side effects was associated with a greater likelihood of stopping [4]. Clinical notes most often cited side effects and cost as reasons [4]. Feeling unsupported does not help either, and that is something we can work on in consultations.

Do people who stop usually start again?

Many do. In the same cohort, between 36% and 47% of those who stopped restarted within a year, depending on whether or not they had diabetes [4]. By two years, the figure was between 46% and 57% [4].

The more weight people regained after stopping, the more likely they were to start again [4]. This is why a cycle is described: treatment stops, weight is regained and treatment starts again [5].

A Cleveland Clinic study followed almost 8,000 people who stopped semaglutide or tirzepatide between 3 and 12 months. Among those taking it for obesity, 55% had gained weight by one year [6]. Only 14% of the whole group attended appointments to work on their habits [6].

This stage is better prepared for before it arrives. Find out how in how to avoid weight regain after Ozempic or Wegovy.

Which questions come up most often in consultations?

We are not sharing anyone’s opinions here about whether the medication works well or badly for them. That is assessed by the person who prescribes it, with your progress in view. The questions that do come up week after week are these.

• “If I have hardly any appetite, how can I get enough protein?” With small, regular meals, and by starting with the protein on your plate.
• “Do I need to follow a diet at the same time?” The medication reduces appetite, but it does not decide what you eat. Without a plan, it is easy to eat less of everything, including protein.
• Worrying about weight regain before even starting. People ask how to avoid it from the first month, while there is still time to prepare healthy habits.

People also ask why someone else taking the same medication has a different experience. It often depends on the dose, how long they have been taking it and what they eat.

Why is a social media post no substitute for a trial?

A comment describes one person’s experience. A trial controls who takes part, the dose, the duration and what the treatment is compared with. This makes it possible to find out whether an effect is caused by the medication or would have happened anyway.

A viral post does not say what dose the person writing it takes, how long they have been on treatment or what they eat. For the full picture, including funding and what to expect at each stage, see the main guide to GLP-1 medicines.

What difference can support from a registered dietitian make?

Spain’s reference guideline on obesity, from SEEDO, recommends a multidisciplinary approach, with nutrition as part of the team [7]. In practice, this means keeping an eye on protein and strength training to preserve muscle. It also means adjusting meals when your appetite almost disappears and preparing for stopping treatment before it happens.

If you are concerned about losing strength as well as weight, find out more in protein and muscle with a GLP-1. We do not prescribe or change your dose: we work on what happens around the medication, before, during and after treatment.