Fact-checked by the Peptide Authority Editorial Board · Last reviewed: 17 May 2026

GLP-1 medicines (UK)

UK GLP-1 Centre — weight-loss and diabetes medicines

Plain-English UK guidance on the GLP-1 receptor agonist medicines — semaglutide (Wegovy / Ozempic), tirzepatide (Mounjaro), liraglutide (Saxenda / Victoza). Patient-pathway view: access routes, prescriber interactions, side-effect literacy, and counterfeit-pen safety. For the regulatory analysis, see the UK Law hub.

Brand guides

Active ingredients

Semaglutide (active ingredient)

Pharmacology, UK access pathways, the Wegovy / Ozempic / Rybelsus split.

Tirzepatide (active ingredient)

Dual GLP-1 / GIP mechanism. Trial data, side-effect picture, UK pathway.

Liraglutide (active ingredient)

Daily-injection GLP-1; Saxenda for weight, Victoza for diabetes.

Comparisons

Mounjaro vs Wegovy

Tirzepatide vs semaglutide head-to-head. Trial outcomes, NHS pathways, practical decision factors.

Wegovy vs Ozempic

Same drug, different licences, different supply chains. Why one isn't a substitute for the other.

Side effects

Mounjaro side effects (UK)

Common, less common, serious, and red flags. UK patient reference.

GLP-1 nausea

Why it happens, the dose-step curve, what helps in practice.

GLP-1 constipation

Under-reported. The fluid / fibre / laxative escalation ladder and bowel-obstruction red flags.

GLP-1 gallbladder risk

Trial signal, mechanism, symptoms to recognise, when to seek urgent care.

GLP-1 pancreatitis

Red-flag symptoms, what to do, why a history of pancreatitis matters.

GLP-1 pregnancy & fertility

Contraindicated in pregnancy. Washout, contraception, and restored-fertility risk.

Side-effect literacy

Overview across the GLP-1 class. Yellow Card reporting.

Access and supply

NHS access pathway

Tier 3 weight-management services, NICE criteria, GP referral.

Private clinics — what good looks like

Registration checks for evaluating a private prescriber.

NHS vs private GLP-1

Cost vs eligibility vs speed. The honest trade-off.

Talking to your GP

Questions for before, during, and after a GLP-1 prescription.

GLP-1 shortages & supply

Why GLP-1s run short, what to do if yours is unavailable, why grey market is the wrong answer.

Counterfeits and reporting

Fake Mounjaro pens

Feb 2026 MHRA alert on falsified 15 mg KwikPens. Identifiers and reporting.

Fake Ozempic pens

Counterfeit Ozempic patterns and what to check.

Fake Wegovy pens

FixDose pen format, counterfeit patterns, what to check before injecting.

Fake Saxenda pens

Daily multi-dose pen format. Lower counterfeit volume but still on MHRA's radar.

Fake retatrutide pens

No licensed reference product exists. Every retatrutide vial sold outside a trial is by definition unverified.

Check a UK online pharmacy (GLP-1)

The six-check protocol before paying for a GLP-1 prescription.

What to do if your pen looks wrong

The immediate action ladder. Stop, photograph, report — don't inject.

Bought from social media — what to do

Action ladder for the Instagram / TikTok / Telegram supply path. Chargeback, Action Fraud, platform reporting.

Practical use

Storage and travel

Refrigeration, in-use limits, insulin coolers, airports, what to do if the cold chain breaks.

Investigational (not licensed)

Retatrutide UK status

Investigational triple-agonist (GLP-1 / GIP / glucagon). Lawful access via clinical trial only.

Cagrilintide UK status

Long-acting amylin analogue. CagriSema combination with semaglutide. Investigational.

Amycretin UK status

Single-molecule GLP-1 / amylin co-agonist. Early-stage investigational.

Semaglutide and UK law — regulatory analysis.
Tirzepatide and UK law — regulatory analysis.
Fake weight-loss pens and UK law — MHRA enforcement.
How to check a UK pharmacy — GPhC / PSNI register lookup.
GLP-1 medicines FAQ — 15 common questions answered.

Brand guides

Wegovy UK guide

Mounjaro UK guide

Ozempic UK guide

Saxenda UK guide

Rybelsus UK guide

Active ingredients

Semaglutide (active ingredient)

Tirzepatide (active ingredient)

Liraglutide (active ingredient)

Comparisons

Mounjaro vs Wegovy

Wegovy vs Ozempic

Side effects

Mounjaro side effects (UK)

GLP-1 nausea

GLP-1 constipation

GLP-1 gallbladder risk

GLP-1 pancreatitis

GLP-1 pregnancy & fertility

Side-effect literacy

Access and supply

NHS access pathway

Private clinics — what good looks like

NHS vs private GLP-1

Talking to your GP

GLP-1 shortages & supply

Counterfeits and reporting

Fake Mounjaro pens

Fake Ozempic pens

Fake Wegovy pens

Fake Saxenda pens

Fake retatrutide pens

Check a UK online pharmacy (GLP-1)

What to do if your pen looks wrong

Bought from social media — what to do

Practical use

Storage and travel

Investigational (not licensed)

Retatrutide UK status

Cagrilintide UK status

Amycretin UK status

Related

Brand guides

Wegovy UK guide

Mounjaro UK guide

Ozempic UK guide

Saxenda UK guide

Rybelsus UK guide

Active ingredients

Semaglutide (active ingredient)

Tirzepatide (active ingredient)

Liraglutide (active ingredient)

Comparisons

Mounjaro vs Wegovy

Wegovy vs Ozempic

Side effects

Mounjaro side effects (UK)

GLP-1 nausea

GLP-1 constipation

GLP-1 gallbladder risk

GLP-1 pancreatitis

GLP-1 pregnancy & fertility

Side-effect literacy

Access and supply

NHS access pathway

Private clinics — what good looks like

NHS vs private GLP-1

Talking to your GP

GLP-1 shortages & supply

Counterfeits and reporting

Fake Mounjaro pens

Fake Ozempic pens

Fake Wegovy pens

Fake Saxenda pens

Fake retatrutide pens

Check a UK online pharmacy (GLP-1)

What to do if your pen looks wrong

Bought from social media — what to do

Practical use