The GLP-1 space is loud, commercially driven, and full of content designed to get you to buy something. Every pharmacy has a guide about their own medications. Every clinic has a success story. Almost none of it tells you the things you actually need to know before committing to a year of weekly injections and thousands of pounds.
This article tries to fill that gap. We don't sell medications. We don't earn a commission based on which provider you choose. What follows is what we'd tell a friend who came to us asking where to start.
What GLP-1 medications actually are
GLP-1 stands for glucagon-like peptide-1 — a hormone your gut produces naturally after you eat. Its job is to signal fullness to your brain, slow the emptying of your stomach, and help regulate blood sugar. For most people, this signal is relatively brief and easy to override. GLP-1 medications work by mimicking this hormone in a much more persistent, sustained way.
The two you'll hear most about in the UK are:
- Mounjaro (tirzepatide) — made by Eli Lilly. Targets both GLP-1 and a second hormone called GIP, which also plays a role in appetite and fat metabolism. This dual action is why it tends to produce higher average weight loss than semaglutide alone.
- Wegovy (semaglutide) — made by Novo Nordisk. Targets GLP-1 only. The same active ingredient as Ozempic, which is licensed for type 2 diabetes — Wegovy is the weight management version, licensed at higher doses.
Both are once-weekly injections administered via a pre-filled pen into the fatty tissue of your stomach, thigh, or upper arm. Both start at very low doses and escalate gradually over several months. Neither is a pill — though an oral version of Wegovy was approved in the US in early 2026 and may come to the UK later this year.
You may have heard of Ozempic — it's the same active ingredient as Wegovy (semaglutide) but licensed for type 2 diabetes management, not weight loss. Some providers prescribe it off-label for weight loss; others specifically use Wegovy. For most patients, the clinical effect is very similar. The licensing distinction matters for NHS access and some insurance purposes.
Cutting through the noise
Before anything else, it helps to know what to ignore. The GLP-1 market has attracted a lot of noise — some of it actively misleading.
"Lose 20% of your body weight" — this is a population average from controlled clinical trials, not a guarantee. Some people lose significantly more; some lose much less. Individual response varies enormously.
On average, both medications produce meaningful, clinically significant weight loss that far exceeds what diet and exercise alone typically achieve for most people with obesity.
"Start losing weight from day one" — appetite suppression can begin quickly, but measurable weight loss takes weeks. The first month is primarily about letting your body adjust.
Most people notice a significant change in their relationship with food — reduced hunger, earlier fullness — within the first 2–4 weeks, often before the weight loss becomes visible.
"Safe and well-tolerated" — true in the sense that serious adverse events are rare, but the majority of people experience gastrointestinal side effects, particularly in the early months.
For most people, side effects are manageable and improve significantly after the first few weeks at each dose. The titration schedule exists specifically to minimise them.
Are you eligible?
For private prescription in the UK, both Mounjaro and Wegovy require a clinical assessment. The licensed criteria are:
- BMI of 30 or above — or BMI of 27 or above with at least one weight-related health condition (such as high blood pressure, type 2 diabetes, sleep apnoea, or high cholesterol)
- No contraindications — including personal or family history of medullary thyroid cancer or certain pancreatic conditions
- Not pregnant, trying to conceive, or breastfeeding
Some providers prescribe at BMI 27 without a listed comorbidity, or even down to BMI 25 in certain cases — but this is off-label prescribing, meaning outside the medication's licensed indication. That doesn't make it unsafe or wrong; off-label prescribing is legal and common in the UK when a clinician judges it appropriate. But it requires a more detailed clinical justification and should be clearly discussed with you before starting. If a provider offers you treatment at a lower BMI without explaining this distinction, that's a gap in their process.
These thresholds are often 2.5 points lower for certain South Asian, East Asian, Black African, and Black Caribbean ethnic groups, who face higher cardiovascular risk at lower BMI levels.
A questionnaire alone is not sufficient for prescription. GPhC guidance requires a clinically appropriate assessment — prescribers must be able to properly evaluate your suitability, which goes well beyond an online form. This might include a telephone or video consultation, or verified photo-based weight assessment, depending on the provider. What it cannot be is a self-reported form with no clinical review. Providers who issue prescriptions on that basis are not following good practice guidance. Avoid them.
NHS access
NHS access is currently very limited. Mounjaro has been available through NHS GP practices since June 2025, but only for patients with the highest clinical need — initially BMI 40+ with four or more weight-related health conditions. This is expanding gradually over a 12-year rollout, but for most people who want to start treatment now, private prescription is the realistic route.
Wegovy is available through NHS specialist weight management services (Tier 3) but typically requires a GP referral and faces long waiting times.
What a legitimate provider looks like
This is the section most guides skip entirely — probably because it's bad for business to tell you what to watch out for.
The UK GLP-1 market has attracted a number of providers that cut corners on clinical assessment, supply chain, or follow-up care. Some operate within the rules; some operate on the edges; some are actively problematic. The MHRA has reported counterfeit GLP-1 pens circulating in the UK, typically sold through unregulated online channels at unusually low prices.
A legitimate provider will:
- Be registered with the General Pharmaceutical Council (GPhC) — you can verify this at pharmacyregulation.org
- Require a genuine clinical consultation, not just a form — a real conversation with a registered prescriber who reviews your medical history
- Supply medication in original Eli Lilly (Mounjaro) or Novo Nordisk (Wegovy) packaging, as pre-filled injection pens
- Offer follow-up support — either included or clearly available — not just dispatch and disappear
- Publish their prices transparently, including consultation fees and delivery
- Not pressure you to commit to long subscriptions before you know how you respond
If you receive anything other than an original pre-filled auto-injector pen, do not use it. Legitimate Mounjaro comes in the KwikPen. Legitimate Wegovy comes in the FlexTouch pen. Vials, syringes, or anything requiring mixing are not licensed products. Report them to the MHRA via the Yellow Card scheme.
What the first weeks actually feel like
Most guides either oversell this (transformative from day one) or scare you with a list of side effects. The honest answer is somewhere more human than either.
Week 1
Your first injection is at the lowest possible dose — 2.5mg for Mounjaro, 0.25mg for Wegovy. The purpose of this dose is purely to introduce the medication to your system. Don't expect dramatic weight loss. Many people feel little to nothing; some feel mild nausea, usually in the day or two after the injection; some notice a modest reduction in appetite.
Weeks 2–4
This is when most people notice the most significant change in their relationship with food. The constant background hum of hunger that many people with obesity describe — always thinking about the next meal, finding it hard to feel satisfied — often quietens substantially. Portions that previously felt insufficient start to feel like enough. Some people find foods they previously craved no longer interest them.
This shift in appetite is what the medication actually does. The weight loss is the downstream effect — the appetite change is the mechanism.
Months 2–5 (titration)
Both medications increase in dose approximately every four weeks. Each dose increase is the most likely time to experience side effects — your body is adjusting again. By the time you reach your maintenance dose (typically 5–6 months in), most people have found a rhythm and the side effects have significantly reduced.
Month 6 onwards
Weight loss typically plateaus somewhat as you approach your body's new set point on the medication. This is normal and doesn't mean the medication has stopped working — it means you've reached a stable state. Some people stay here; others discuss with their prescriber whether a higher dose is appropriate.
Managing side effects honestly
Gastrointestinal side effects affect the majority of people to some degree — nausea, constipation, diarrhoea, bloating, and indigestion are all common, particularly in the early weeks and after each dose increase. For most people, these are manageable. For some, they're significant enough to require reducing or pausing the dose.
Some practical things that genuinely help:
- Eat smaller portions — the medication slows gastric emptying; large meals on top of that causes significant discomfort
- Avoid fatty, greasy, or very rich foods — particularly in the early weeks; they're much harder to tolerate
- Stay hydrated — constipation is a common side effect and dehydration makes it worse
- Don't rush dose increases — both medications allow staying at a lower dose longer if needed; there's no benefit to pushing through severe nausea
- Pick a consistent injection day — and avoid it being a day before something where nausea would be a problem
Contact your prescriber or call 111 immediately if you experience severe or persistent abdominal pain — this can be a sign of pancreatitis, a rare but serious potential side effect. Also seek immediate help for signs of allergic reaction (facial swelling, difficulty breathing). Both medications are black triangle drugs — new or novel, subject to enhanced post-market monitoring. Report any unusual side effects via the Yellow Card scheme at yellowcard.mhra.gov.uk.
One important note for women on the contraceptive pill: the MHRA advises using an additional non-oral contraceptive method while taking these medications, as GLP-1 treatments may reduce the absorption of oral contraceptives. Discuss this with your prescriber before starting.
The thing most people don't realise
The medications work while you take them. When you stop, the hormonal effect stops — and for most people, appetite returns to pre-treatment levels within weeks to months. A 2026 BMJ meta-analysis found that people who stopped GLP-1 medications regained the majority of lost weight within one to two years of stopping.
These are not a course of treatment that leaves you cured. They're more like glasses — they work while you wear them.
This isn't a reason not to start. For many people, the health benefits during treatment are significant and lasting — improvements in blood pressure, blood sugar, and cardiovascular risk markers that persist even if some weight is regained after stopping. But it's information you need before you decide, not after.
What this means practically:
- Think about sustainability from the start — which provider and price point can you realistically maintain long-term?
- Use the period of treatment to build habits — providers that include coaching, nutrition support, or behaviour change programmes tend to produce better long-term outcomes after stopping
- Have a plan — discuss with your prescriber what the long-term strategy looks like, not just the titration schedule
Questions to ask before you start
A good provider will answer all of these questions willingly. Evasiveness, pressure to commit quickly, or surprise fees not disclosed upfront are all warning signs worth taking seriously.
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