GLP-1 Myths and Facts

Many popular claims about GLP-1 medicines such as Mounjaro (tirzepatide) and Wegovy (semaglutide) are oversimplified, and some are simply wrong. In short: these medicines are not a quick fix or a cosmetic shortcut, but they are not uniquely dangerous either. Weight regain after stopping is common but not universal. Muscle loss happens but can be reduced. "Natural GLP-1" supplements are not equivalent. This guide checks common myths against trial evidence, SmPCs and regulator advice, so you can talk to a prescriber with accurate information.

Myths about how GLP-1 medicines work

Myth: "They melt fat away."

Fact: GLP-1 medicines do not burn or dissolve fat directly. They act mainly on appetite: they increase fullness, reduce hunger and slow stomach emptying. Weight loss comes from eating less over time. Our guide to what GLP-1 medications are explains the mechanism in plain English.

Myth: "Mounjaro is just a stronger Ozempic."

Fact: They are different molecules. Ozempic and Wegovy contain semaglutide, which acts on GLP-1 receptors. Mounjaro contains tirzepatide, which acts on both GIP and GLP-1 receptors. In the head-to-head SURMOUNT-5 trial, tirzepatide produced greater average weight loss than semaglutide 2.4mg, but individual responses vary, and some people do better on one than the other. Ozempic is licensed only for type 2 diabetes. See our comparison of Mounjaro and Wegovy.

Myth: "Ozempic and Wegovy are the same thing, so it doesn't matter which you use."

Fact: They contain the same active ingredient but are separate products with different licences, doses and pens. Wegovy is licensed for weight management; Ozempic is licensed for type 2 diabetes. Using diabetes products for weight loss has been discouraged, partly because it contributed to supply problems for people with diabetes. See Ozempic vs Wegovy.

Myth: "Tablets don't work as well as injections."

Fact: It depends on the tablet. In the OASIS 4 trial, oral semaglutide 25mg produced average weight loss of around 14% over 64 weeks, broadly similar to semaglutide injections in earlier trials. Orforglipron produced average weight loss of around 11% at its highest dose over 72 weeks. Both were approved by the MHRA for weight management in 2026. Trials differ, so direct comparisons are approximate. See our guide to oral vs injectable GLP-1s.

Myth: "Everyone loses 20% of their body weight."

Fact: Figures such as around 15% for semaglutide 2.4mg (STEP 1) and around 20% for the highest dose of tirzepatide (SURMOUNT-1) are trial averages. Some people lose much more, while others lose much less, and a minority lose very little. Results in everyday practice may differ from tightly supervised trials. See our guide to realistic weight loss expectations.

Myths about who they are for

Myth: "They're just a vanity drug."

Fact: UK licences cover adults with obesity, or overweight with weight-related health conditions, alongside diet and activity. Obesity is linked to type 2 diabetes, heart disease, sleep apnoea, osteoarthritis and some cancers. The SELECT trial found semaglutide reduced major cardiovascular events in people with obesity and established heart disease. Prescribing to people outside licensed criteria for cosmetic reasons is not in line with the licence or responsible practice. See our guide to obesity as a chronic disease.

Myth: "Using medication is cheating; you just need willpower."

Fact: After weight loss, the body responds with hormonal and metabolic changes that increase hunger and favour regain. Genes, environment, sleep, stress and other medicines all influence weight. Using a licensed medicine for obesity is no more cheating than using medicine for high blood pressure. Equally, medication is not necessary or right for everyone.

Myth: "Anyone can have them if they pay."

Fact: GLP-1 medicines are prescription-only. A prescriber must assess whether you meet the criteria and whether treatment is safe for you. Regulated providers should verify your identity and weight and ask about your medical history and other medicines. Our guide to why online pharmacies verify ID and weight explains why these checks matter.

Myths about results and stopping

Myth: "Once you stop, you regain everything."

Fact: Many people regain a substantial amount, but not necessarily all. In the STEP 1 extension, participants who stopped semaglutide had regained around two-thirds of the weight they had lost within a year, on average. In withdrawal trials such as STEP 4 and SURMOUNT-4, people switched to placebo regained much more than those who continued. Individual results vary. See our guide to weight regain after stopping.

Myth: "If you regain weight, the treatment failed."

Fact: Weight regain after stopping reflects the biology of obesity, in the same way that blood pressure rises when blood pressure tablets are stopped. It does not mean the treatment did not work while it was being taken, or that the person failed. Discussing the long-term plan with your prescriber before starting is sensible. See our guide to long-term GLP-1 use.

Myth: "A plateau means the medicine has stopped working."

Fact: Weight loss on GLP-1 medicines typically slows and levels off after many months, usually around a year or more into treatment. This is expected, as the body reaches a new balance. A plateau does not necessarily mean the medicine has stopped working; stopping it often leads to regain. See our guide to weight loss plateaus.

Myths about side effects and safety

Myth: "Everyone feels terrible on them."

Fact: Gastrointestinal side effects such as nausea, diarrhoea, constipation and vomiting are common, especially when starting and after dose increases, but they are usually mild to moderate and often ease over time. Many people experience few side effects. Gradual dose increases, smaller meals and avoiding rich food help. A minority stop treatment because of side effects. See our guide to managing nausea.

Myth: "They're completely safe because they're licensed."

Fact: Licensing means the MHRA judged that benefits outweigh risks for the licensed population, not that there are no risks. Uncommon but serious side effects include pancreatitis and gallbladder problems. Dehydration from vomiting can affect the kidneys. They should not be used in pregnancy. Long-term data in weight management are still accumulating. See our guides to pancreatitis risk and gallbladder problems.

Myth: "They're dangerous and cause cancer."

Fact: In rodent studies, GLP-1 medicines caused thyroid C-cell tumours. The relevance to humans is uncertain, and a clear link in people has not been established. The product information advises caution in people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2. Research on other cancers is ongoing, with mixed findings. Tell your prescriber about your history, and report symptoms such as a neck lump or persistent hoarseness.

Myth: "GLP-1 medicines cause depression and suicidal thoughts."

Fact: Regulators, including the European Medicines Agency, have reviewed reports of suicidal thoughts in people taking GLP-1 medicines. In April 2024, the EMA's safety committee concluded that the available evidence did not support a causal link. Monitoring continues. Mood can be affected by many things during weight loss, so anyone with a history of mental health problems, or who notices changes, should speak to their prescriber. See our guide to GLP-1 medication and mental health.

Myth: "'Ozempic face' is a unique side effect of the drug."

Fact: Changes in facial appearance, often called "Ozempic face", appear to result from losing fat from the face, which happens with substantial weight loss by any method. It is not thought to be a direct effect of the medicine. Age, genetics and the speed and amount of weight loss all play a part. See our guide to facial changes and loose skin.

Myth: "All the weight you lose is muscle."

Fact: Body composition studies from the main trials show most weight lost is fat, but a meaningful share is lean tissue, which includes muscle. This happens with substantial weight loss by any method. Eating enough protein and doing regular strength exercise help protect muscle, which matters especially for older adults. See our guide to preserving muscle on GLP-1 treatment.

Myth: "Hair loss means the medicine is poisoning you."

Fact: Hair thinning can occur during rapid weight loss of any kind, usually as a temporary shedding condition called telogen effluvium. It typically appears a few months after the start of significant weight loss and often recovers. Low protein or iron intake can contribute. See our guide to Mounjaro and hair loss.

Myth: "It's fine to stop and start whenever you like."

Fact: Missing several doses can mean you need to restart at a lower dose to avoid strong side effects, according to the SmPC rules. Stopping and restarting repeatedly may make side effects more troublesome. Talk to your prescriber before pausing. See our guide to a Mounjaro missed dose.

Myth: "You don't need to tell anyone you're taking it."

Fact: You should tell your GP, any surgeon or anaesthetist, and your dentist if you are having sedation. GLP-1 medicines slow stomach emptying, which matters for anaesthesia, and the MHRA has highlighted that people treated privately may not mention their medicine unless asked. See our guide to GLP-1 medication before surgery.

Myths about diet and lifestyle

Myth: "You can eat whatever you want."

Fact: Appetite is reduced, but what you eat still matters for comfort, health and long-term results. Large, fatty or very sugary meals are more likely to trigger nausea, reflux and vomiting. Low protein increases the risk of muscle loss. UK licences require use alongside a reduced-calorie diet. See our guide to what to eat on GLP-1 medication.

Myth: "You don't need to exercise."

Fact: Physical activity is part of every UK licence for these medicines. Exercise, especially strength training, helps protect muscle and bone, improves fitness and mood, and may help with weight maintenance. See our exercise guide.

Myth: "Alcohol is fine because it doesn't interact."

Fact: Alcohol is not a listed direct interaction, but it can worsen nausea and reflux, adds calories, contributes to dehydration, and can raise the risk of low blood sugar in people taking insulin or sulfonylureas. Heavy drinking is a risk factor for pancreatitis. See our guide to Mounjaro and alcohol.

Myths about alternatives and shortcuts

Myth: "Natural GLP-1 supplements work just as well."

Fact: Supplements marketed as "natural GLP-1", including some fibre products, probiotics and plant extracts such as berberine, have not been shown to produce weight loss comparable to licensed medicines in robust trials. They are regulated as food supplements, not medicines, so their claims and contents are not assessed in the same way. Some foods, such as protein and fibre, can modestly influence gut hormones and fullness, which is a useful part of a healthy diet but very different from a licensed medicine.

Myth: "Microdosing gives the benefits without the side effects."

Fact: Microdosing, taking doses lower than those in the licence, has not been properly tested for weight management. There is no good evidence about its benefits or risks. It often involves dividing pens in ways they were not designed for, or using unlicensed products. Your prescriber may keep you at a lower licensed dose if it is working well, which is different and follows the SmPC.

Myth: "Pens from social media or salons are the same as from a pharmacy."

Fact: The MHRA has repeatedly warned about fake and unlicensed weight loss products, including counterfeit pens and so-called research peptides. These may contain the wrong dose, the wrong substance or contaminants, and people have been harmed. Prescription-only medicines should only come from a regulated pharmacy after a consultation. See our guide to fake weight loss jabs.

Myth: "New medicines like retatrutide are already available."

Fact: Retatrutide, CagriSema and amycretin were still in development and not licensed in the UK at the time of writing. Products claiming to contain them that are sold online are unlicensed, and their contents cannot be verified. See our guide to the GLP-1 pipeline.

Myths about access

Myth: "You can't get them on the NHS."

Fact: NHS access exists but is limited. NICE recommends Wegovy within specialist weight management services (TA875) and Mounjaro in primary care with a phased rollout (TA1026), starting with people who have the highest clinical need. Availability varies by area. See our guide to private vs NHS weight loss treatment.

Myth: "All online providers are the same."

Fact: Regulated online providers differ in their consultation process, monitoring, support and how they communicate with your GP. All should be registered with the appropriate regulators, such as the General Pharmaceutical Council for pharmacies and the Care Quality Commission for prescribing services in England. Our provider comparison explains how services differ, and our guide to who regulates online weight loss services explains the checks. Costs vary and change over time; we do not list prices in our guides, but our price comparison explains what affects cost.

Myths about specific groups

Myth: "GLP-1 medicines are only for people with diabetes."

Fact: GLP-1 medicines were first developed for type 2 diabetes, and some products, such as Ozempic and Rybelsus, are licensed only for diabetes. But Wegovy, Mounjaro, liraglutide (Saxenda), Wegovy tablets and Foundayo are licensed for weight management in adults who meet BMI criteria, whether or not they have diabetes. See our overview of every weight loss medication available in the UK.

Myth: "They don't affect fertility or contraception."

Fact: Tirzepatide may reduce the effectiveness of oral contraceptives, and the MHRA advises a non-oral or additional barrier method for four weeks after starting and after each dose increase. Weight loss can also improve fertility in some women, for example those with polycystic ovary syndrome, so unplanned pregnancies are possible. GLP-1 medicines should not be used in pregnancy or while trying to conceive. See our guides to contraception and pregnancy and fertility.

Myth: "You're too old for weight loss injections."

Fact: UK licences for Mounjaro and Wegovy set no upper age limit for adults, and age alone does not require a different dose. Older adults do need careful assessment, particularly for muscle loss, dehydration, kidney function and other medicines. See our guide to GLP-1 medication for people over 65.

How to judge a claim you read online

Claims about GLP-1 medicines spread quickly on social media. A few questions can help you judge them:

• Who is making the claim? Is it a regulator, NHS body, published trial or qualified clinician, or someone selling a product?
• Is it based on a trial or on anecdotes? Individual stories, including before-and-after pictures, cannot show what is typical.
• Is the figure an average? Trial results describe groups, not what will happen to any one person.
• Does it apply to the UK? Licences, doses and products differ between countries.
• Is it current? Guidance on medicines changes. Check the SmPC on medicines.org.uk, the MHRA and NICE.
• Is someone trying to sell you something? Urgency, discount codes or "no consultation needed" are warning signs.

Myths and facts at a glance

For related reading, browse our frequently asked questions guides, or visit our hubs for weight loss injections and oral GLP-1 tablets.

When to speak to a professional

Speak to your GP, a pharmacist or your prescriber if:

• you are unsure whether something you have read about GLP-1 medicines is accurate
• you are considering treatment and want to understand whether it suits you
• side effects are troublesome or not settling
• you notice changes in mood, or have a history of depression or an eating disorder
• you are planning a pregnancy or could become pregnant

Seek urgent medical help (call NHS 111, or 999 in an emergency) if you are taking a GLP-1 medicine and have:

• severe, persistent abdominal pain, which may spread to your back, with or without vomiting
• pain in the upper right abdomen with fever or yellowing of the skin or eyes
• signs of severe dehydration, such as very little urine, confusion or fainting
• thoughts of harming yourself; you can also contact Samaritans on 116 123
• signs of a severe allergic reaction, such as swelling of the face or throat, or difficulty breathing

Suspected side effects, and suspected fake products, can be reported to the MHRA through the Yellow Card scheme.