Long-Term GLP-1 Use: What the Evidence Shows

Long-term use of Mounjaro, Wegovy and other GLP-1 medicines is increasingly common, and the evidence now extends to around three to four years. Trials show that weight loss is broadly maintained while treatment continues, that semaglutide reduces major cardiovascular events in people with heart disease (SELECT), and that tirzepatide sharply reduces progression from prediabetes to type 2 diabetes. Known risks, such as gallbladder problems and pancreatitis, remain, and regulators continue to update safety information. Decisions about how long to continue belong with your prescriber. This guide summarises what we know and what remains uncertain.

Why long-term use is being discussed

For most people, GLP-1 medicines work while they are taken. Trials such as STEP 4 and SURMOUNT-4 showed that stopping treatment usually leads to weight regain, and the STEP 1 extension found that most of the lost weight returned within a year. This has led to obesity being treated more like other chronic conditions, such as high blood pressure or type 2 diabetes, where ongoing treatment is often needed to maintain benefits. Our guides to weight regain after stopping GLP-1 medication and obesity as a chronic disease explain this in more detail.

Long-term use raises reasonable questions: does the effect last? Is it safe? What does it cost? What monitoring is needed? The sections below address each.

How long the evidence extends

Weight over time

The pattern across trials is consistent. Weight falls steadily over the first months, slows, and then levels off at around 60 to 72 weeks. While treatment continues, this lower weight is broadly maintained, although some people regain a little over time. Average loss in SELECT (around 10%) was lower than in STEP 1 (around 15%). SELECT enrolled an older population with established heart disease and did not include an intensive lifestyle programme, which may explain some of this difference.

Our guide to weight loss plateaus explains why levelling off is expected.

Cardiovascular outcomes: the SELECT trial

SELECT, published in the New England Journal of Medicine in 2023, enrolled 17,604 adults aged 45 or over with established cardiovascular disease and a BMI of 27 or more, but without diabetes. Over an average follow-up of around 40 months, semaglutide 2.4 mg reduced the combined risk of cardiovascular death, non-fatal heart attack or non-fatal stroke by about 20% compared with placebo. Following this trial, Wegovy's UK licence was extended to include reducing cardiovascular risk in some adults. Read more in our guide to Wegovy and the SELECT trial.

Tirzepatide's cardiovascular outcome trials have been in progress. At the time of writing, check the current Mounjaro SmPC for its licensed indications.

Diabetes prevention

In the three-year SURMOUNT-1 extension, published in 2025, people with prediabetes and obesity who took tirzepatide were much less likely to develop type 2 diabetes than those on placebo (around 1% compared with around 13%). This is one of the strongest arguments for long-term treatment in people at high risk of diabetes, although some of the benefit faded after treatment was stopped at the end of the study.

Long-term safety: what we know

All medicines carry risks. The following are the main long-term considerations for GLP-1 medicines, based on product information and regulatory updates. The SmPCs on medicines.org.uk contain the full list.

Gastrointestinal side effects

Nausea, diarrhoea, constipation, vomiting and indigestion are the most common side effects. They tend to be most noticeable during dose increases and often lessen over time. For many people they are mild by the maintenance phase, but some people continue to experience them. Our guides to nausea and constipation offer practical advice.

Gallbladder problems

Gallstones and gallbladder inflammation occur more often with GLP-1 medicines than with placebo. Rapid weight loss itself increases the risk. Symptoms include pain in the upper right abdomen, often after meals, fever and yellowing of the skin or eyes. See our guide to GLP-1 medicines and gallbladder problems.

Pancreatitis

Acute pancreatitis is an uncommon but potentially serious side effect. In February 2026 the MHRA strengthened its warnings on severe acute pancreatitis with GLP-1 and GIP/GLP-1 medicines, reminding people to seek urgent help for severe, persistent abdominal pain that may spread to the back. It also highlighted that privately prescribed medicines may not appear in GP records, so it is important to tell healthcare professionals you are taking one. See our guide to GLP-1 medicines and pancreatitis risk.

Eye health: NAION with semaglutide

In February 2026 the MHRA updated product information for semaglutide medicines (Wegovy, Ozempic and Rybelsus) to include a very rare risk of non-arteritic anterior ischaemic optic neuropathy (NAION), a condition that causes sudden, usually painless, loss of vision in one eye. The MHRA estimated it may affect up to 1 in 10,000 people taking semaglutide. Anyone with a sudden change in eyesight while taking semaglutide should seek urgent care at eye casualty or A&E.

People with type 2 diabetes and existing diabetic eye disease may also need closer eye monitoring when blood glucose improves rapidly.

Muscle and bone

Weight loss from any cause includes some loss of lean mass, including muscle, alongside fat. Body composition studies within the STEP 1 and SURMOUNT-1 trials found that most of the weight lost was fat, but lean mass made up a meaningful minority. Over the long term, preserving muscle through adequate protein and resistance exercise is important, especially for older adults. See our guide to preserving muscle on GLP-1 medication. Evidence on long-term bone health is still developing.

Nutrition

Eating less over long periods increases the risk of inadequate intake of protein, vitamins and minerals if diets are not balanced. Our guides on what to eat on GLP-1 medication and vitamins and supplements cover this.

Thyroid

In rodent studies, GLP-1 medicines caused thyroid C-cell tumours. It is not known whether this applies to humans, and large human studies have not confirmed a clear link. The SmPCs include related cautions, and prescribers will take your personal and family history into account.

Mental health

Regulators, including the European Medicines Agency, have reviewed reports of suicidal thoughts with GLP-1 medicines and, at the time of writing, have not found evidence of a causal link. Anyone experiencing low mood or suicidal thoughts should seek help promptly. See our guide to GLP-1 medicines and mental health.

Surgery and anaesthesia

Because GLP-1 medicines slow stomach emptying, there may be a risk of inhaling stomach contents during anaesthesia or sedation. Always tell the surgical or anaesthetic team that you take one. See our guide to GLP-1 medicines, surgery and anaesthesia.

What remains uncertain

• Effects beyond four or five years. Very long-term data, over decades, are not yet available.
• The most effective maintenance strategy. Whether lower doses, longer intervals or switching to tablets can maintain results as well as full-dose treatment is still being studied.
• Effects in groups under-represented in trials, such as older adults with frailty, people with multiple health conditions, and some ethnic groups.
• Cardiovascular outcomes for tirzepatide in people without diabetes, at the time of writing.
• Effects of repeated stopping and restarting.

Licensing and NHS duration

The UK licences for Mounjaro and Wegovy don't set a fixed maximum duration of treatment for weight management. However:

• NICE TA875 (semaglutide) recommends NHS treatment within specialist weight management services for a maximum of two years.
• NICE TA1026 (tirzepatide) doesn't set the same two-year limit. NHS tirzepatide has been rolled out in phases, including in primary care from June 2025.
• Both NICE appraisals recommend considering stopping if less than 5% of starting weight is lost after six months on the highest tolerated dose.

These are NHS funding decisions, not statements that longer use is unsafe. Private prescribers make individual decisions. Our guide to private versus NHS weight-loss treatment explains the differences.

The cost of long-term treatment

For people paying privately, long-term treatment is a significant financial commitment, and prices have changed over time, including the September 2025 rise in the UK list price of Mounjaro. Factors that affect long-term cost include the medicine and dose, whether consultations and follow-up are included, and how prices change over the years. We don't quote prices in our guides, but you can compare services on our prices page and read our guide to the long-term cost of GLP-1 treatment.

Monitoring on long-term treatment

Good long-term care includes regular review. Depending on your health, this may involve:

Ask your prescriber what monitoring they provide. If you're treated privately, keep your GP informed so your records are accurate. You can compare the follow-up offered by regulated providers on our providers page.

More guides on this subject are available in our long-term topic hub and the wider guides library.

Long-term use in specific groups

The balance of benefits and risks may differ for some groups. The following points are general; your prescriber will consider your individual circumstances.

Older adults

Older people are at greater risk of losing muscle and becoming frail, and may also be more affected by dehydration. Long-term treatment in older adults needs particular attention to protein, strength exercise, hydration and other medicines. See our guide to GLP-1 medicines over 65.

People with type 2 diabetes

GLP-1 medicines have been used for many years in type 2 diabetes, so there is more long-term experience in this group. Long-term use may allow other diabetes medicines to be reduced, but people taking insulin or sulfonylureas need monitoring for low blood sugar, and people with diabetic eye disease may need closer eye checks. See our guide to GLP-1 medicines and type 2 diabetes.

People planning a family

GLP-1 medicines should not be used during pregnancy, and the SmPCs advise stopping them before a planned pregnancy. This means long-term treatment may need to be paused for a period. Planning ahead with your prescriber is important. See our guide to GLP-1 medicines, pregnancy and fertility.

People with heart disease

For people with established cardiovascular disease and overweight or obesity, the SELECT trial provides evidence that long-term semaglutide reduces major cardiovascular events. This may weigh in favour of continued treatment, in discussion with the person's cardiology team.

Myths about long-term use

"These medicines are too new to know anything about long-term safety"

Semaglutide and other GLP-1 medicines have been used in type 2 diabetes for many years, and weight-management trials now extend to around four years. There is still much to learn, particularly beyond that timeframe, but there is a substantial body of evidence.

"Long-term use damages your metabolism"

There is no good evidence that GLP-1 medicines permanently damage metabolism. Weight regain after stopping reflects the return of the body's natural appetite and energy signals, not damage caused by the medicine.

"Once you start, you can never stop"

You can stop at any time, ideally with your prescriber's support. The evidence suggests that many people regain weight after stopping, which is something to plan for, but stopping is always a choice.

"Long-term use is unsafe because the NHS only allows two years"

NICE's two-year limit for semaglutide under TA875 was based on the evidence and cost-effectiveness information available when it was assessed. It is a funding decision, not a safety limit.

Making a long-term plan

If you and your prescriber agree that long-term treatment is right for you, a clear plan helps. It might cover:

• How often you'll have reviews, and what will be checked
• Your target dose, and whether a lower maintenance dose might be appropriate
• How you'll manage side effects if they return
• What you'll do about nutrition and muscle preservation
• How cost fits into your plans, if you're paying privately
• When you would consider stopping, and how that would be managed
• How to keep your GP and other healthcare professionals informed

Revisiting the plan every six to twelve months, or when your circumstances change, keeps it relevant.

Balancing benefits and uncertainties

Deciding whether to continue long term involves weighing known benefits against known risks and remaining uncertainties. The balance looks different for different people.

Your prescriber can help you work through these factors. Decisions can be revisited as new evidence emerges or your circumstances change.

When to speak to a professional

Speak to your prescriber, GP or pharmacist if:

• You want to review whether to continue, reduce or stop treatment
• Side effects persist or worsen over time
• You notice weight regain while still on treatment
• You develop a new health condition or start a new medicine
• You are planning surgery, a procedure with sedation, or a pregnancy
• You feel low in mood, anxious or have thoughts of self-harm

Seek urgent medical help (NHS 111, or 999 in an emergency) if you have:

• Severe, persistent abdominal pain that may spread to your back, with or without vomiting (possible pancreatitis)
• Upper right abdominal pain with fever, or yellowing of the skin or eyes (possible gallbladder problems)
• A sudden change or loss of vision, especially in one eye: go to eye casualty or A&E urgently
• Repeated vomiting or diarrhoea with signs of dehydration
• Signs of a severe allergic reaction, such as swelling of the face, lips or throat, or difficulty breathing
• Thoughts of suicide or self-harm: contact NHS 111, your GP or Samaritans (116 123), or call 999 if you are in immediate danger