RecruitingPhase IIIInterventional

A study looking at whether metformin (a diabetes drug) can prevent weight gain caused by antipsychotics in people experiencing their first episode of psychosis

When people start medicines for their first episode of psychosis, they can sometimes gain a lot of weight. This extra weight can lead to other health problems like heart issues or diabetes, and it can also make people feel bad about themselves or want to stop their medication. Metformin is a well-known medicine used for diabetes that has shown some promise in preventing this weight gain in smaller studies. This new, larger study will help us understand if metformin can really prevent or reduce weight gain for people starting antipsychotic medication for the first time. We hope the results will help healthcare professionals better support people in the future.

At a glance

Status

Recruiting

Phase

Phase III

Sponsor

Pennine Care NHS Foundation Trust

Enrolment target

340

Start

01 Jun 2026

Estimated completion

31 Aug 2027

Antipsychotic induced weight gain in first episode psychosis

What is this study about?

Many people in the UK experiencing psychosis are given special medicines called antipsychotics to help manage their symptoms. While these medicines are really helpful, a common side effect is gaining a lot of weight. This weight gain isn't just about how you look; it can lead to other serious health problems later on, like heart disease or diabetes. It can also make people feel uncomfortable or unhappy with their body, which might even make them want to stop taking their important medication.

Metformin is a medicine that has been used for over 60 years to treat diabetes. Some smaller studies have suggested that it might also be helpful in preventing the weight gain caused by antipsychotics and reducing the risk of developing diabetes. This study, called METRIC, is a bigger research project designed to properly test this idea. We want to find out if metformin can effectively stop or reduce the amount of weight people gain when they start antipsychotic medication for their first episode of psychosis.

By carefully comparing people who take metformin with those who don't, we aim to get a clear answer. The results of this study will be very important. If metformin works, it could give doctors a new way to help people manage their weight while still getting the benefits of their antipsychotic medication. This could improve their overall health and make it easier for them to continue their treatment.

Key takeaways

A study to see if metformin can stop weight gain from antipsychotics.
For adults experiencing their first episode of psychosis who recently started medication.
Participants will take either metformin or a dummy pill for one year.
Regular check-ups will monitor weight and overall health.
Helps future patients by finding better ways to manage medication side effects.
Funded by the National Institute for Health and Care Research (NIHR).

Who may be eligible?

This study is looking for around 340 adults aged between 16 and 65 years old. To take part, you must be experiencing psychosis for the first time and have started taking your antipsychotic medication within the last four weeks. We also expect that you plan to continue taking your antipsychotic medication for at least a year. The study will take place in about 15 different mental health services across the UK.

There are some reasons why you might not be able to join. For example, if you are currently taking metformin, have certain health conditions like diabetes, severe kidney or liver problems, or if you are already underweight. Also, if you've been actively trying to manage your weight through a special programme in the last three months, you might not be suitable for this study.

We want to make sure the study is safe for everyone and that we can get clear results. Your doctor or the study team will check all these details with you to see if you are a good fit for this research.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you an adult aged 16 to 65?
Have you recently (within 4 weeks) started medication for your first episode of psychosis?
Do you plan to continue your psychosis medication for at least a year?
Do you have a healthy weight and are not significantly underweight?
Are you free from diabetes or severe kidney/liver problems?
Have you NOT been in a special weight-loss programme recently?

Answer every question to see your result.

What does participation involve?

If you decide to take part in this study, you'll be randomly put into one of two groups. One group will take metformin tablets for a year, and the other group will take a 'dummy' tablet called a placebo. A placebo looks just like metformin but doesn't contain any active medicine. Neither you nor your doctor will know which tablet you are taking until the study has finished, which helps us see the true effect of metformin.

During the study, you'll have regular check-ups with your mental health team every three months for a year while you're taking the tablets. After you stop taking the tablets, you'll continue to have check-ups for up to another six months. These visits will involve measuring your weight, checking on your mental health symptoms, and asking how you're generally feeling about your health. We'll also ask if you've visited any other services for your psychosis or weight.

Potential risks and benefits

Taking part in this study means you might receive metformin, which has a low risk of side effects. We will conduct some blood tests to carefully monitor your health and ensure the medication isn't causing any problems. While metformin might not directly benefit you, as we don't yet know if it will truly prevent weight gain, your participation is incredibly valuable. By helping us find answers, you will contribute to improving how future patients with first-episode psychosis manage weight gain, helping many others. You are free to withdraw from the study at any time without affecting your medical care.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

Sites currently being identified
City only
-, England

Common questions

What is psychosis?

Psychosis is a mental health condition where a person might have difficulty telling what's real from what's not. They might see, hear, or believe things that aren't real.

What is an antipsychotic medication?

These are medicines used to help manage the symptoms of psychosis. They can help reduce confusion and make it easier to think clearly.

What is metformin?

Metformin is a medicine commonly used to treat type 2 diabetes. It helps the body use insulin more effectively and can sometimes lead to weight loss.

What is a 'placebo'?

A placebo is a 'dummy' pill that looks just like the real medicine but contains no active ingredients. It's used in studies to compare against the active drug.

How long will I be in the study?

You'll take either metformin or a placebo for one year, and then have follow-up check-ups for up to six months after that. So, the total time in the study could be up to 18 months.

How to find out more

Sienna Hamer-Kiwacz

METRIC_RCT@sheffield.ac.uk - Official trial record

Always speak to your GP or specialist before deciding to take part in a study.