What are GLP-1 medicines?
GLP-1 medicines are prescription medicines that help some people manage weight and/or type 2 diabetes by reducing appetite, changing how quickly food leaves the stomach, and improving blood sugar control. In everyday UK chat they're often called "weight loss jabs", but the proper term is usually GLP-1 receptor agonists (and closely related medicines, like tirzepatide, that act on more than one hormone pathway).
- The plain-English meaning of “GLP-1” (and what it does in your body)
- How these medicines work (and why side effects happen)
- The most common GLP-1 medicines in the UK (Wegovy, Ozempic, Mounjaro, Saxenda)
- What research shows about stopping treatment and weight regain
- The practical reason maintenance is harder than the “early months”
GLP-1 medicines vs “weight loss jabs” (the language problem)
People often use “GLP-1” as a catch-all for newer weight management injections, but there are two useful distinctions:
- GLP-1 receptor agonists (examples: semaglutide, liraglutide) mimic a natural hormone called GLP-1.
- Dual-acting medicines (example: tirzepatide) act on GLP-1 and another gut hormone pathway (GIP). NICE treats tirzepatide as a recommended option for weight management for eligible adults, but it's not technically “GLP-1 only”.
If you're writing or talking about these medicines in a way that's accurate and easy to understand, “GLP-1 medicines” is fine — just note that some newer injections are dual-acting. For a full list of terms, see the GLP-1 glossary.
How GLP-1 medicines work (in plain English)
GLP-1 medicines mimic (or amplify) signals your body already uses after eating. In practice, that tends to show up in a few ways:
- You feel full sooner (and for longer): they act on appetite and satiety pathways in the brain, which can reduce “food noise” for some people.
- Food leaves your stomach more slowly: slower gastric emptying can increase fullness, but it can also contribute to nausea in the early stages.
- Blood sugar regulation improves: they increase insulin release in response to food and reduce glucagon, which helps manage blood glucose (this is why they were originally developed for type 2 diabetes).
- For dual-acting medicines (e.g., tirzepatide): there's additional activity on the GIP pathway, which may contribute to greater average weight loss in trials (still with individual variation).
Common GLP-1 medicines in the UK
Below is a practical “name mapping” table because most confusion online is just brand names versus ingredients.
| Ingredient | Brand name (UK) | Typical use | How it's taken |
|---|---|---|---|
| Semaglutide | Wegovy | Weight management | Injection (weekly) |
| Semaglutide | Ozempic | Type 2 diabetes | Injection (weekly) |
| Tirzepatide (dual GIP/GLP-1) | Mounjaro | Type 2 diabetes and weight management (NICE-approved for eligible adults) | Injection (weekly) |
| Liraglutide | Saxenda | Weight management | Injection (daily) |
This is not an exhaustive list. There are other GLP-1 medicines used for diabetes, and what's appropriate depends on your clinical context. See the GLP-1 glossary for more terms.
What results look like in studies (and what that does not promise)
Trials give a useful “order of magnitude”, but they're averages under specific conditions (and you're a person, not a mean).
- In a large trial of semaglutide 2.4 mg for adults with overweight/obesity, mean weight change at 68 weeks was −14.9% versus −2.4% with placebo (with lifestyle intervention in both groups).
- In a major trial of tirzepatide, mean weight change at 72 weeks ranged from roughly −15.0% to −20.9% depending on dose, versus −3.1% with placebo.
That doesn't mean you “should” lose those percentages (or that it will feel easy). It does mean: these medicines can be powerful tools, but outcomes vary, and the long-term question becomes, “How do you maintain what you've built?” Read more about GLP-1 weight loss in the UK.
Side effects and safety (common vs serious)
- Common side effects are often gastrointestinal (nausea, vomiting, diarrhoea, constipation).
- Less common but more serious risks exist (for example, gallbladder disease and pancreatitis), and the MHRA has strengthened and reiterated warnings around acute pancreatitis (including rare severe cases).
UK safety points
- Only get these medicines through legitimate channels. The MHRA has warned about falsified/counterfeit weight-loss pens in the UK and advises using prescription routes only.
- Report side effects via the Yellow Card scheme — this is how safety signals get picked up at population level.
If you have symptoms that could indicate something serious (particularly severe, persistent abdominal pain), treat that as an “ask for urgent clinical advice” situation rather than trying to self-interpret. Learn more about what Healthcount does and does not do.
Why maintenance matters (and what happens when you stop)
Early weight loss can feel like momentum; maintenance is the part where small drifts compound.
One reason maintenance deserves its own plan is that stopping treatment is often followed by weight regain. In the STEP 1 trial extension, participants regained about two-thirds of prior weight loss one year after stopping semaglutide (with cardiometabolic markers trending back too). Read the full evidence on weight regain after stopping GLP-1.
So, when people talk about “willpower”, it's often missing the point — obesity is chronic, and the body pushes back. The useful question becomes: what low-burden system helps you spot drift early, before it becomes a full reset?
Learn more about GLP-1 maintenance and why people stop GLP-1.
Where Healthcount fits (clear boundaries)
Healthcount is quiet-by-design. Think of it like a sat-nav for GLP-1 maintenance: it stays quiet when things look stable, and it nudges you when signals suggest drift (so you can act early, rather than after weeks of slippage).
- Low-burden signals: no daily food logging, no “perfect tracking” pressure
- Maintenance-first: designed around the months and years after the initial momentum
- Clear boundaries: Healthcount does not prescribe, diagnose, or advise dose changes; it supports maintenance and signposts you back to clinical support when needed
See how Healthcount works and our clinical boundaries.
Questions to ask your prescriber
If you're considering or already using a GLP-1 medicine, these questions may be useful at your next appointment:
- Which medicine is most appropriate for my circumstances, and why?
- What side effects should I expect, and when should I contact you?
- How long is the treatment likely to last, and what's the plan for maintenance?
- What happens if I need to stop or miss doses?
- Are there lifestyle changes that can support long-term outcomes alongside this medicine?
Frequently asked questions
Sources
- NICE semaglutide guidance (TA875)
- NICE tirzepatide guidance (TA1026)
- STEP 1 semaglutide trial (New England Journal of Medicine)
- SURMOUNT-1 tirzepatide trial (New England Journal of Medicine)
- Weight regain after withdrawal (STEP 1 extension study)
- MHRA safety updates and counterfeit warnings
Last updated: March 2026. For our editorial approach, see our clinical boundaries and Privacy & UK GDPR.
Learn about GLP-1 maintenance
Understand what drift looks like and how to respond — or request a pilot if you're an insurer or employer.