GLP 1 Drugs for Weight Loss: What They Are and How Suitability Is Decided

GLP-1 medicines have changed weight management considerably, and they have also generated more misinformation than almost any other group of medicines in recent years.

Two things are worth settling straight away. Every GLP-1 medicine licensed in the UK is prescription only, with no exceptions. And there is no single medicine in this group that is the right answer for everyone, which is why the question of which one suits you is a clinical one rather than a shopping one.

This page explains what these medicines are, how they work, what determines suitability, what they do not do, and what is actually being sold by anyone offering them without a prescription.

Key things to know

• GLP-1 medicines mimic a natural gut hormone that affects appetite, fullness and how quickly the stomach empties.
• All are prescription only medicines in the UK. None is available over the counter, including the oral form.
• There is no single best option. Suitability depends on your medical history, other conditions, other medicines and how you respond.
• The MHRA has found illegally sold pens containing insulin rather than the labelled medicine, and people have been hospitalised as a result.
• The most common side effects are digestive and often occur when treatment starts or the dose increases. Some side effects may persist, and serious reactions can occur less commonly.
• These medicines work alongside changes to eating, activity and sleep, not instead of them.
• Weight tends to return after stopping unless the wider changes are maintained. That is a known limitation, not a failure.

What are GLP-1 medicines?

GLP-1 medicines are treatments that act like a natural hormone called glucagon-like peptide-1, which the gut releases after eating. These GLP-1 agonists were developed to treat type 2 diabetes, and some are now licensed for weight management.

The hormone has several jobs. It helps regulate blood glucose by stimulating insulin secretion and suppressing the release of glucagon to help stabilise blood sugar levelsIt can slow stomach emptying and help regulate blood glucose, while its effects on appetite and fullness can reduce food intake.

Medicines in this group produce a longer-lasting version of those effects.

How do they cause weight loss?

Mainly by reducing appetite and food intake. People report feeling full sooner, staying full for longer, and thinking about food less.

The slowed stomach emptying contributes to feeling full, and it also explains most of the common side effects. The appetite effect is the more important one and is why intake falls even when someone is not consciously restricting.

This matters for expectations. These medicines make eating less feel easier, but long-term maintenance still depends on lifestyle changes. They do not replace a healthy diet or regular exercise.

Which medicines are in this group?

In the UK, semaglutide is available under different brand names and for different licensed uses. Wegovy is authorised for weight management, while Ozempic and Rybelsus have diabetes indications. Tirzepatide (Mounjaro) acts on both the GLP-1 and GIP receptors. Liraglutide is available under several brand names, with its licensed use depending on the specific product. Foundayo (orforglipron) is an oral medicine authorised in the UK for weight management and type 2 diabetes. Always check the individual product's licence rather than assuming that all brands containing the same active ingredient have the same indications.

Can you get GLP-1 medicines over the counter?

No. Every GLP-1 medicine licensed in the UK, including GLP-1 medications used for weight loss, is a prescription only medicine. There is no over the counter version, no pharmacy-counter version, and no legal route to obtain one without a prescription from a qualified prescriber, following a consultation with a doctor or qualified prescriber.

This is the most important answer on this page, because the searches that ask it are the searches most likely to end in harm.

What about the tablet version?

In June 2026 the MHRA authorised an oral semaglutide treatment for weight management, making semaglutide tablets available in the UK for the first time as an alternative to injections; some people may also see this described as the Wegovy pill.

It is still a prescription only medicine. A tablet format changes how the medicine is taken, not its legal status or the need for clinical assessment and monitoring, and oral tablets are still not available over the counter.

There is a specific risk attached to this. A tablet is easier to package convincingly and post than a refrigerated injection pen, so the arrival of an oral option creates a new opportunity for illegal sellers. Anything offered as a GLP-1 tablet without a prescription should be treated as fake.

What are people actually being sold?

When a GLP-1 medicine is offered without a prescription, one of three things is happening.

1. A genuine medicine supplied illegally, with no assessment, no monitoring and no way to know whether it is safe for the person taking it.
2. A falsified product, with counterfeit packaging and contents that may not match the label at all.
3. An unlicensed preparation, such as powder in a vial requiring mixing. There is no authorised GLP-1 product supplied as a powder to be reconstituted at home, so anything of that description is not a legitimate medicine.

The MHRA has reported that some illegally supplied pens were found to contain insulin rather than the labelled medicine. For someone without diabetes, that causes dangerously low blood sugar, and people have been hospitalised as a result.

The regulator has also confirmed that a falsified product reached patients through an online pharmacy in the UK, which is the clearest possible demonstration that professional-looking packaging and a professional-looking website prove nothing.

How can I tell whether a seller is legitimate?

Check the supplier rather than the product. Packaging can be copied. Registration cannot.

• The pharmacy should appear on the General Pharmaceutical Council register, with a registration number and trading address you can match
• You should be asked detailed questions about your medical history, other medicines and other conditions
• Online supply should still require a valid private prescription, and a prescriber should review your answers and be able to decline
• Some routes to treatment may require referral to a specialist weight management service; in some settings, Wegovy may require referral to a specialist for prescribing
• The medicine should arrive in its original manufacturer packaging, with a patient information leaflet
• Injectable GLP-1 medicines require refrigerated storage and should be shipped accordingly

Treat these as warning signs: no prescription required, no clinical questions, sales through social media or a beauty or aesthetics setting, powder requiring mixing, pressure tactics or bulk discounts, or a price far below what registered pharmacies charge.

The MHRA and the Advertising Standards Authority have both acted against businesses promoting prescription only weight loss medicines to the public, so aggressive advertising is itself a signal worth noticing.

Which GLP-1 is best for weight loss?

There is no single weight-loss medicine that is best for everyone. Clinical trials have reported different average weight losses for medicines such as Mounjaro, Wegovy and Foundayo, but the results cannot be compared directly without considering the dose, study population, duration and trial design.

For example, results reported in a clinical trial do not predict exactly how much weight an individual will lose in routine care. Suitability depends on medical history, other medicines, tolerability, licensed indications and response to treatment.

The most useful question is which treatment is appropriate and safe for you, rather than which medicine has the largest headline figure.

What actually determines which treatment suits someone?

An assessment considers all of the following, and any one of them can change the answer.

This is why a clinical assessment exists, and why comparison charts on the internet cannot answer the question for you.

Why comparing headline results is misleading

Trial results are averages across selected populations, and different trials use different participants, different comparisons and different durations. Placing two headline figures side by side and concluding that one medicine is better is not a fair comparison.

Individual variation is also wide. Within any trial, some participants lose a great deal of weight and some lose very little, and the average conceals both. Results vary between individuals, and your own response cannot be predicted from a published number.

The more useful question is not which medicine produces the biggest average, but which treatment you can tolerate, stay on safely, and combine with changes you can maintain.

Side effects: what to expect

The most common side effects of GLP-1 medicines are digestive. Nausea, vomiting, diarrhoea and constipation are common, along with headache and tiredness.

Rare but serious side effects can occur, including acute pancreatitis. Seek urgent medical attention if you develop severe, persistent abdominal pain, particularly if it spreads to your back, whether or not you also have nausea or vomiting. If pancreatitis is suspected, stop taking the medicine and seek urgent medical advice. Treatment should not be restarted if pancreatitis is confirmed, in line with MHRA guidance.

Rare but serious problems can also include vision changes such as non-arteritic anterior ischemic optic neuropathy.

Gallstones, dehydration from persistent vomiting or diarrhoea, and allergic reactions are also recognised. Your patient information leaflet lists every reported effect with how often it occurs.

Who these medicines are not suitable for

Suitability is decided individually, but some situations always require careful assessment or rule treatment out. These medicines are intended for managing overweight and to treat obesity under clinical supervision, not for cosmetic weight loss.

• Pregnancy, breastfeeding, or planning a pregnancy. The MHRA advises effective contraception while taking weight loss medicines of this type, and notes that vomiting and diarrhoea can reduce absorption of oral contraceptives
• A history of pancreatitis, where the MHRA advises caution
• Certain thyroid and endocrine conditions and family histories
• Severe gastrointestinal disease, including significant problems with stomach emptying
• Current or past eating disorders, where weight loss treatment can be harmful and other support is needed
• Some combinations with diabetes medicines, which need review before starting
• Being below the licensed criteria for treatment, including cases where these medicines are not appropriate for obese individuals under the relevant prescribing criteria

For many medicines licensed for weight management, adults may be eligible if their BMI is 30 or above, or if their BMI is 27 to below 30 and they have at least one weight-related health condition. The precise criteria depend on the medicine and its licence, and a prescriber must assess whether treatment is appropriate.

What GLP-1 medicines do not do

Being clear about the limits is as important as describing the benefits.

They do not maintain weight loss by themselves. Weight commonly returns after stopping unless eating patterns, activity and sleep have changed alongside. Stopping treatment often allows appetite to return towards normal and can lead to rapid weight regain. Weight regain is common after stopping GLP-1-based weight-management treatment, although the amount varies between individuals. Appetite may increase again, making it harder to maintain weight loss. This is why long-term support and a plan for maintaining results matter.

They do not protect muscles. Weight lost includes lean muscle mass as well as fat. Resistance activity and adequate protein matter throughout treatment, and matter more with age.

They do not treat the reasons people eat. Where eating is driven by distress, habit or circumstance, those drivers remain and need their own attention.

They do not work equally for everyone. Some people respond very well, some modestly, and some not at all. Results vary between individuals.

They are not cosmetic products. The MHRA has been clear that medicines of this type are licensed for specific medical conditions, are not intended for aesthetic use, and have not been assessed as safe when used that way.

What a proper assessment involves

A legitimate online consultation with UK registered prescribers should cover your medical history, current medicines, allergies, other conditions, height and weight, and your previous experience of weight management, as a proper assessment forms part of a personalised treatment plan.

The prescriber reviews your answers and decides whether treatment is appropriate and can support weight loss safely and appropriately, which includes being able to say no or ask for more information. If treatment is supplied, there should be a route back for review, monitoring and reporting side effects.

Treatment suitability depends on an individual clinical assessment, and your prescriber will determine the appropriate treatment. These medicines should only be used under the supervision of an appropriately qualified prescriber.

Red flags: when to seek medical advice

Seek urgent medical attention for severe, persistent abdominal pain that may spread to your back; swelling of the face, lips, tongue or throat; difficulty breathing; or signs of significant dehydration, such as passing very little urine, dizziness on standing or unusual drowsiness. Sudden vision loss or a sudden change in vision also requires urgent medical assessment.

Contact your prescriber promptly for persistent vomiting or diarrhoea, pain in the upper right abdomen particularly after eating, symptoms of low blood sugar if you take diabetes medicines, sudden vision changes, or side effects that are not settling. While some GLP-1 receptor agonists are linked to cardiovascular protection against heart attacks and strokes, that does not change the need for urgent assessment if severe symptoms develop.

If you have taken a product obtained without a prescription and feel unwell, seek medical advice and say what you have taken. Be straightforward about it. Clinicians need the information, not an explanation.

Medical Disclaimer

The information in this article reflects UK guidance available at the time of review. Licensing, prescribing criteria and safety advice can change, so readers should check the latest MHRA guidance and the patient information leaflet for their specific medicine.

All GLP-1 medicines licensed in the UK are prescription only medicines. They should only be used under the supervision of an appropriately qualified prescriber, following a clinical assessment that considers your medical history, current medicines and other conditions. Treatment suitability depends on an individual clinical assessment, and results vary between individuals.

Do not obtain these medicines without a prescription. Products supplied outside the regulated system are not covered by MHRA oversight and their contents, strength and storage cannot be relied upon.

Seek urgent medical attention if you develop severe and persistent stomach pain that may spread to your back, swelling of the face, lips, tongue or throat, difficulty breathing, or signs of significant dehydration.

Suspected side effects can be reported through the Yellow Card scheme, which the MHRA uses to monitor the safety of medicines.