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Guide 2 of 9 · Stage: Understand

What do GLP-1 medicines do?

How semaglutide (Wegovy, Ozempic) and tirzepatide (Mounjaro) work in your body, what they can and can't do, the risks, and what is licensed in the UK.

GLP Guidebook teamUpdated 12 Oct 202613 min read45 sourcesWritten from published sources
The short answer

GLP-1 stands for glucagon-like peptide-1, a hormone your gut makes after you eat. GLP-1 medicines copy it. They help you feel full sooner, slow your stomach and help control blood sugar. Most weight loss comes from eating less. Common side effects are feeling sick and diarrhoea, and weight usually returns after stopping. Talk to a doctor before starting, stopping or changing one.

Key facts

What they are
Medicines that copy GLP-1, a gut hormone1
Main ones in the UK
  • Semaglutide: Wegovy (injection and tablets), Ozempic, Rybelsus2,3
  • Tirzepatide: Mounjaro4
  • Liraglutide: Saxenda and generic versions5,6
  • Orforglipron: Foundayo, a daily tablet, since August 20267
Licensed in the UK for
  • Type 2 diabetes: Ozempic, Rybelsus, Trulicity and others
  • Weight management: Wegovy, Saxenda
  • Both: Mounjaro and Foundayo2,8,4,7
How weight loss happens
Mostly by eating less. They don't speed up the calories you burn at rest.9
Main risks
Feeling sick, diarrhoea and vomiting are common. Rarer serious risks include pancreatitis and gallbladder problems. See the risks, in brief10,11
Prescription
Yes, all of them are prescription-only medicines. You can get one through the NHS if you meet its criteria, or from a private prescriber, who must check your weight and height properly first.3,12,13
On this page
  1. What does GLP-1 mean?
  2. What do the medicines do in your body?
  3. Why do people lose weight on them?
  4. Do the results hold for people of different ethnic backgrounds?
  5. How is this different from metformin and other diabetes pills?
  6. Who these are for, and who they're not for
  7. Which GLP-1 medicines are licensed in the UK?
  8. Is Ozempic the same as Wegovy?
  9. How long do they take to work, and how long do they last?
  10. Do they do anything besides weight and sugar?
  11. What these medicines do not do
  12. Are these medicines new?
  13. Questions people ask

What does GLP-1 mean?

GLP-1 is short for glucagon-like peptide-1. It's a hormone your gut releases after you eat, telling your body that food has arrived.

It's made mostly in the lower part of your small intestine and in your large intestine.1 It sends signals to your brain, stomach and pancreas (an organ behind your stomach that makes hormones).

Your body's own GLP-1 doesn't last long. An enzyme (a protein that breaks other things down) clears it in about 1 to 2 minutes.1 So its natural effect is small and short.

What do GLP-1 medicines do in your body?

A GLP-1 medicine is a lab-made version of GLP-1, changed so your body can't break it down quickly. Your own GLP-1 is gone in 1 to 2 minutes. Semaglutide, the medicine in Wegovy and Ozempic, keeps working for about a week.1,10

So the "food has arrived" message that your gut normally sends for a few minutes after a meal is sent all day, every day, and more strongly.

Your own GLP-1Made by your gut after you eatGone in 1 to 2 minutes
A GLP-1 medicineA weekly injection or a daily tabletKeeps sending the message all week

The message reaches four parts of your body

BrainYou feel less hungryThe part of your brain that controls appetite is told you've eaten, so you want less food and feel full sooner.Helps with weight
StomachYou stay full for longerYour stomach empties more slowly, so a meal stays with you longer before you feel hungry again.Helps with weight
PancreasSugar leaves your blood fasterYour pancreas releases more insulin, the hormone that moves sugar out of your blood. It does this only when your sugar is high.Helps with blood sugar
LiverLess extra sugar is addedYour liver stores sugar and releases it when a hormone called glucagon tells it to. The medicine lowers glucagon when your sugar is high, so the liver adds less.Helps with blood sugar

Simplified. Based on a scientific review of GLP-1 and the US Wegovy label.1,10

In short: the brain and stomach effects are why people eat less and lose weight. The pancreas and liver effects are why these medicines lower blood sugar in type 2 diabetes.

Because the pancreas and liver effects only switch on when sugar is high, the medicine mostly leaves normal sugar levels alone. Sugar can still drop too low if it's taken with insulin or certain other diabetes medicines.10

Why do people lose weight on them?

Mainly because they eat less. In a small study, semaglutide did not change the calories people burned at rest.9

That study gave 30 people semaglutide 1 mg or a dummy injection (one with no medicine in it) for 12 weeks each. On semaglutide, they ate 24% less across a full day of eat-as-much-as-you-like meals.9 They also reported less hunger and fewer food cravings.9

The two biggest weight trials are called STEP 1 (semaglutide, made by Novo Nordisk) and SURMOUNT-1 (tirzepatide, made by Eli Lilly). Each one worked the same way:

  • People were split at random into two groups. One group got the medicine. The other got a dummy injection.
  • Both groups got the same diet and exercise advice, and nobody knew which injection they were on.
  • So the gap between the two groups is what the medicine itself added.14,15

Average weight lost. Kilograms are for someone who starts at 90 kg (14 st 2 lb, or 198 lb).

STEP 1Semaglutide 2.4 mg (Wegovy), weekly

1,961 adults with obesity or overweight, without diabetes. 68 weeks.14

Semaglutide14.9%about 13 kg
Dummy injection2.4%about 2 kg
SURMOUNT-1Tirzepatide 15 mg (Mounjaro), weekly

2,539 adults with obesity or overweight, without diabetes. 72 weeks.15

Tirzepatide20.9%about 19 kg
Dummy injection3.1%about 3 kg

Which works better? You can't tell by comparing the two cards above, because they were different trials with different people. One trial, SURMOUNT-5, tested the two medicines against each other in the same group of people. Each person took the highest dose they could manage. It was paid for by Eli Lilly, the maker of tirzepatide.16 Tirzepatide also acts on a second gut hormone, called GIP (glucose-dependent insulinotropic polypeptide), which may help explain the difference.4

SURMOUNT-5Tirzepatide vs semaglutide, head to head

751 adults with obesity, without diabetes. 72 weeks.16

Tirzepatide20.2%about 18 kg
Semaglutide13.7%about 12 kg

People with type 2 diabetes usually lose less. STEP 2 ran the same test in people with diabetes: about 9 kg lost instead of 13 kg, on the same dose.14,17

STEP 2Semaglutide 2.4 mg, people with diabetes

1,210 adults with overweight or obesity and type 2 diabetes. 68 weeks.17

Semaglutide9.6%about 9 kg
Dummy injection3.4%about 3 kg

All of these are averages. Some people lose much more, and some lose very little.14

RisksThe risks, in brief
44 in 100felt sick on Wegovy, against 16 in 100 on a dummy injection (US label)10
24 in 100vomited on Wegovy, against 6 in 100 on a dummy injection (US label)10
  • Pancreatitis (a swollen, painful pancreas) has been seen. Severe stomach pain that may spread to the back is a warning sign. In January 2026 the MHRA, the UK medicines regulator, updated its advice on this small risk.10,11
  • Gallbladder problems, such as gallstones, are more common.10
  • Dehydration from vomiting or diarrhoea can hurt the kidneys.10
  • Thyroid warning (US label). Semaglutide caused thyroid tumours in rodents. The US label says people with a personal or family history of medullary thyroid cancer, or MEN 2 (a rare inherited condition that causes gland tumours), should not use it.10
  • Not in pregnancy. The MHRA says to stop semaglutide at least 2 months, and tirzepatide at least 1 month, before trying for a baby.2
  • Report side effects to the MHRA's Yellow Card scheme, online or in the Yellow Card app.2,18
Full detail in Guide 5: Side effects and risks →
Weight usually comes back when you stop. In a STEP 1 follow-up, people had lost 17.3% on semaglutide. A year after stopping, they had regained about two-thirds of it, on average.19 More in Guide 9: Stopping

Not all the weight lost is fat. A scan study inside STEP 1 looked at 140 people. On semaglutide, fat fell by about 19% and lean mass by about 10%.20 In other words, people lost about a fifth of their fat and about a tenth of their lean mass. Lean mass means everything that isn't fat. It includes muscle, but also organs, bone and water.21 Guide 8 covers eating and exercise on these medicines.

Do the results hold for people of different ethnic backgrounds?

Trials in East Asian people show similar weight loss. None of the trials on this page was run specifically in South Asian or Black people.

  • Japan and South Korea (401 people, STEP 6): 13.2% of body weight lost on semaglutide 2.4 mg over 68 weeks, against 2.1% on a dummy injection.22
  • China (210 people, SURMOUNT-CN): 13.6% of body weight lost on tirzepatide 10 mg and 17.5% on 15 mg over 52 weeks, against 2.3% on a dummy injection.23
  • Japan (225 people analysed, SURMOUNT-J): people on tirzepatide lost about 16% (10 mg) and 21% (15 mg) more of their body weight than people on a dummy injection, over 72 weeks.24

In England, South Asian people at a BMI of about 24 have the same diabetes risk as white people at 30.25 That's why NICE uses lower BMI thresholds, including for GLP-1 medicines on the NHS, for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background.26,12 Guide 1 explains these thresholds.

How is this different from metformin and other diabetes pills?

GLP-1 medicines lower blood sugar and also reduce appetite. In the NHS they are usually added to other diabetes medicines, not used first.27

Metformin mainly stops your liver releasing too much sugar and helps your body use insulin better. It doesn't make your pancreas release more insulin.28 Since February 2026, NICE has advised starting most adults with type 2 diabetes on metformin plus an SGLT-2 inhibitor (a tablet that makes you pass extra sugar in your urine). It suggests adding a GLP-1 medicine or tirzepatide later in some cases, such as for people living with obesity or with heart and blood-vessel disease.27

HbA1c is a blood test showing your average sugar over the past few months. In a 30-week trial of Ozempic on its own, HbA1c started around 8.1% (65 mmol/mol). It fell by 1.4 to 1.6 percentage points, against 0.1 on a dummy injection.29 That means from about 8.1% to about 6.5–6.7%.

Watch for low blood sugar if you take other diabetes medicines. The risk goes up when GLP-1s are combined with insulin or sulfonylureas.10,29 Sulfonylureas include gliclazide, widely used in the UK, which can cause low sugar itself.30 Doctors may lower the dose of these when starting a GLP-1.10

The type 2 diabetes path covers this in more detail: I have type 2 diabetes.

Who these are for, and who they're not for

In the UK, each brand is licensed for set uses: type 2 diabetes, weight management, or both. Whether one suits you is a decision for you and a doctor.

  • Type 2 diabetes: Ozempic, Rybelsus, Trulicity, Mounjaro, Foundayo and others.2,8,4,7
  • Weight management: Wegovy (injection and tablets), Mounjaro, Saxenda, some generic liraglutide brands, and Foundayo.31,3,4,5,7,2
  • Teenagers: Wegovy is licensed from age 12 for young people with obesity who weigh over 60 kg (9 st 6 lb), alongside diet and activity. Saxenda is also licensed from 12.31,5
  • Heart protection: since July 2024, Wegovy is licensed to lower the risk of heart attack and stroke in adults with heart or blood-vessel disease and a BMI of 27 or more.32,31
  • Fatty liver with scarring (MASH): Wegovy was licensed for adults with this in July 2026.33

The licence rules for weight are a BMI of 30 or more, or 27 to 30 with at least one weight-related condition such as high blood pressure.31,7 The licences don't lower these numbers for any ethnic group. NHS criteria are separate and stricter: for example, NICE recommends Mounjaro on the NHS from a BMI of 35 with at least one weight-related condition, 2.5 lower for some ethnic groups.12,34 These are points to start a conversation with a doctor, not a sign that you qualify.

Not tested in type 1 diabetes. The US Wegovy label says its use in people with type 1 diabetes has not been studied.10 (A label is the official prescribing document for a medicine. In the UK it's called the summary of product characteristics.)

Tirzepatide and the contraceptive pill. Tirzepatide (Mounjaro) can make the pill work less well. The MHRA and NICE say to switch to a non-pill method, or add a barrier method such as condoms, for 4 weeks after starting and for 4 weeks after each dose increase.2,12

They're not for losing a few pounds before a holiday or event. The MHRA says GLP-1 medicines should only be used if you are overweight or have diabetes, not for cosmetic reasons.2 They're long-term treatments, and weight tends to come back after stopping.19,35 If that's you, read I want to lose a few kilos.

Who shouldn't take them, and what to ask, is in Guide 4: Should I consider a GLP-1?

Which GLP-1 medicines are licensed in the UK?

Every GLP-1 medicine has two kinds of name: the name of the medicine itself, and the brand names it's sold under. Knowing the difference stops a lot of confusion.

The medicineWhat actually works in your bodyThe same chemical, whoever makes it. Doctors and labels use this name.
e.g. Paracetamol
The brandThe name on the boxChosen by the company selling it. One medicine can have many brands.
e.g. Panadol, Calpol

GLP-1 medicines work the same way. Semaglutide is the medicine, and Wegovy, Ozempic and Rybelsus are brands of it. Two brands of the same medicine can still differ in dose, in whether they're an injection or a tablet, and in what they're licensed for.

A generic is a copy made by another company once the patent ends. In the UK, liraglutide is the only one of these medicines with generic versions. We found no generic semaglutide licensed here.6

The GLP-1 medicines licensed in the UK, and their brands

MedicineSemaglutide →Weekly injection, or a daily tablet
  • Wegovy injectionNovo Nordisk · weekly injectionFor weight, heart protection and MASH31,33
  • Wegovy tabletsNovo Nordisk · daily tablet, since June 2026For weight management3
  • OzempicNovo Nordisk · weekly injectionFor type 2 diabetes36,2
  • RybelsusNovo Nordisk · daily tabletFor type 2 diabetes2
MedicineTirzepatide →Weekly injection
  • MounjaroEli Lilly · weekly KwikPen injectionFor type 2 diabetes and weight4,37
  • Not ZepboundZepbound is the US weight brand of tirzepatide. In the UK, tirzepatide for weight is Mounjaro.37
MedicineOrforglipronDaily tablet
  • FoundayoEli Lilly · daily tablet, since August 2026. Can be taken at any time of day, with no food or water rules.For weight and type 2 diabetes7
MedicineDulaglutide →Weekly injection
  • TrulicityEli Lilly · weekly injectionFor type 2 diabetes8
MedicineLiraglutide →Daily injection
  • SaxendaNovo Nordisk · daily injectionFor weight management5
  • Generic versionsBiolide, Liraglutide Biocon, Nevolat, Diavic, Plaobes and Zegluxen. What each is licensed for depends on the brand.6,2

Names only, not a recommendation. Victoza, an older liraglutide brand for diabetes, is no longer listed.6 Doses, prices and how to get them are in Guide 6.

UK note: fakes are a real problem. In February 2026 the MHRA warned about a fake Mounjaro 15 mg pen supplied through one UK online pharmacy; it was spotted when the dose knob came off.38 In October 2025 it found the first illegal factory making weight-loss pens in the UK, with more than 2,000 unlicensed pens seized.39 The MHRA says medicines sold as a powder in vials that you mix yourself are not authorised.2 Guide 6 covers safe ways to get them.

Is Ozempic the same as Wegovy?

Same medicine, different brand. Both are semaglutide, made by Novo Nordisk. They are licensed for different uses and go up to different doses.

  • Ozempic is licensed in the UK for type 2 diabetes only. Its highest dose is 2 mg a week.36,2
  • Wegovy is licensed for weight management. Its usual full dose is 2.4 mg a week, and 7.2 mg is allowed for some adults with obesity.31

The MHRA's own table lists Ozempic as not licensed for weight loss.2 Using a medicine for something it isn't licensed for is called "off-label". During the 2023 to 2025 shortage of diabetes GLP-1s, UK prescribers were told to prescribe them only for their licensed use, so that people with diabetes could get them.40 Wegovy is the semaglutide brand licensed for weight.2

Mounjaro is a different medicine: tirzepatide, made by Eli Lilly.4

How long do they take to work, and how long do they last?

You start on a low dose and go up slowly, usually every 4 weeks. Weight loss builds over many months.31,14

In trials, stomach side effects happened mostly while the dose was still going up.15,16

Your prescriber sets your dose. This is the UK label schedule for Wegovy injections, shown so you know what to expect.31
  1. Weeks 1–40.25 mg once a week
  2. Weeks 5–80.5 mg
  3. Weeks 9–121 mg
  4. Weeks 13–161.7 mg
  5. Week 17 on2.4 mg, the usual full dose
  6. If needed7.2 mg, for adults with obesity, after at least 4 weeks on 2.4 mg

In STEP 1, average weight kept falling until about week 60, then levelled off.14 The UK label says that if you haven't lost at least 5% of your starting weight after 6 months, you and your prescriber should decide whether to carry on. NICE uses a similar 5% check on the NHS.31,12

Why once a week, and how long it stays in your body

Your body clears semaglutide slowly. About half of each dose is gone after a week, so one injection a week keeps enough in your blood.1,10

The same slow clearing means the medicine doesn't leave your body the day you stop taking it. After your last dose, it takes about 5 weeks to leave your blood.29

This matters most if you're planning a pregnancy. The MHRA says to stop semaglutide at least 2 months before trying for a baby, to give it time to leave your body.2

Do they do anything besides weight and sugar?

In one large trial, semaglutide lowered the combined risk of heart attack, stroke and heart-related death. Most of that came from fewer heart attacks.

The SELECT trial followed 17,604 people for about 3 years.41 All were 45 or older, had overweight or obesity, and no diabetes. All already had heart or blood-vessel disease: a past heart attack, a past stroke, or narrowed leg arteries.10

6.5 in 100had a heart attack, stroke or heart-related death on semaglutide41
8.0 in 100did on a dummy injection41

That's about 1 fewer event for every 67 people treated. Heart attacks fell from 3.8 to 2.8 in 100. Strokes went from 2.0 to 1.8 in 100, a difference too small to be sure of.10

The MHRA licensed Wegovy for this in July 2024.32 In May 2026, NICE recommended it on the NHS in England for adults with established heart or blood-vessel disease and a BMI of 27 or more.42 It applies to people who already have that disease, not to everyone.

In July 2026, Wegovy was also licensed in the UK for fatty liver with scarring (MASH) in adults.33

What these medicines do not do

  • They're not a cure. On average, people regained two-thirds of the lost weight within a year of stopping.19
  • They don't burn fat. They work by cutting how much you eat, not by speeding up your body.9
  • They're not a short course. WHO treats obesity as a long-term condition needing lifelong care.35
  • They don't replace food changes. NICE says every weight-loss medicine should go alongside a reduced-calorie diet and more activity.12
  • They're not for cosmetic weight loss. The MHRA says not to use them to lose weight for appearance.2

Are these medicines new?

No. The first GLP-1 medicine was approved in the US in 2005. What's new is how strong and long-lasting they've become, and that some now come as tablets.43,3

The first one, exenatide, came from a substance found in the saliva of a lizard, the Gila monster.1 Later versions were changed to last longer in the body. Half of each semaglutide dose is cleared in about a week.1,10

  1. 2005Exenatide (Byetta) approved in the US43
  2. Sep 2023Wegovy launches in the UK44
  3. Nov 2023Mounjaro licensed in the UK for weight management37
  4. Jul 2024Wegovy licensed for heart protection32
  5. Dec 2024NICE recommends Mounjaro for weight on the NHS, rolled out in stages34
  6. Jan 2026Wegovy 7.2 mg dose licensed45
  7. Jun 2026Wegovy tablets licensed for weight3
  8. Jul 2026Wegovy licensed for MASH33
  9. Aug 2026Foundayo (orforglipron) licensed, first in Europe7

Questions people ask

What does GLP-1 stand for?

Glucagon-like peptide-1. It's a hormone your gut makes after you eat.1

Can I get Ozempic for weight loss in the UK?

Ozempic is licensed in the UK for type 2 diabetes only.2 Wegovy is the same medicine, semaglutide, licensed for weight management.31 See Ozempic vs Wegovy.

Is a GLP-1 medicine the same as insulin?

No. Insulin lowers blood sugar directly. GLP-1 medicines help your body release its own insulin when sugar is high, and they also reduce appetite.1

Why is it an injection once a week?

Half of each semaglutide dose is cleared in about a week, which is why it's taken once a week.1,10 Your own GLP-1 lasts 1 to 2 minutes.1 Some newer versions are daily tablets instead.3,7

Can food or supplements do the same thing?

Eating does release your own GLP-1, but your body clears it within minutes.1 The medicines are built to last about a week.10 The MHRA warns never to buy them from beauty salons or through social media.2

Do I need a prescription in the UK?

Yes. They are prescription-only medicines.3 On the NHS, Mounjaro for weight can be prescribed by GPs in England for people in the groups being offered it first, while Wegovy and Saxenda for weight come through specialist weight services.12,34 Private online services must check your weight and height properly, for example by video call or from your GP records, not from a questionnaire alone.13 Guide 6 explains the routes.

Before you move on

  • GLP-1 medicines mostly work by making you eat less.
  • Wegovy and Ozempic are both semaglutide; Mounjaro is tirzepatide.
  • Stomach side effects are common, and there are rarer serious risks.
  • They're long-term. Weight usually returns after stopping.
  • In the UK they're prescription-only, through the NHS or a properly checked private prescriber.
Side effects and risksShould I consider a GLP-1?I have type 2 diabetes
Was this guide easy to understand?

Sources

  1. Müller TD et al. Glucagon-like peptide 1 (GLP-1). Molecular Metabolism, 2019;30:72–130. doi:10.1016/j.molmet.2019.09.010 · PMID 31767182
  2. MHRA. GLP-1 medicines for weight loss and diabetes: what you need to know (includes which brands are licensed for what, the gap before pregnancy and advice on the pill). Updated 5 February 2026. gov.uk
  3. MHRA. First GLP-1 tablet for weight loss approved in the UK (Wegovy tablets). 11 June 2026. gov.uk
  4. Eli Lilly. Mounjaro KwikPen, summary of product characteristics (UK label). Date of revision 29 August 2026. emc
  5. Novo Nordisk. Saxenda, summary of product characteristics (UK label). Date of revision 11/2025. emc
  6. Electronic Medicines Compendium (emc), search for "liraglutide": lists Biolide, Liraglutide Biocon, Nevolat, Diavic, Plaobes and Zegluxen; Victoza not listed. Checked 12 October 2026. emc
  7. MHRA. UK first in Europe to authorise orforglipron for weight management and type 2 diabetes. 10 August 2026. gov.uk
  8. Eli Lilly. Trulicity, summary of product characteristics (UK label). emc
  9. Blundell J et al. Effects of once-weekly semaglutide on appetite, energy intake, control of eating, food preference and body weight in subjects with obesity. Diabetes, Obesity and Metabolism, 2017;19:1242–51. doi:10.1111/dom.12932
  10. Novo Nordisk. Wegovy (semaglutide) prescribing information, US label (FDA), revised June 2026. Not the UK label. DailyMed
  11. MHRA. MHRA updates guidance for GLP-1 prescribers and patients (risk of severe acute pancreatitis). 29 January 2026. gov.uk
  12. NICE. Overweight and obesity management (NG246), section "Medicines and surgery", table 1. Last updated 8 January 2026. nice.org.uk
  13. General Pharmaceutical Council. Online pharmacies to strengthen safeguards to prevent unsafe supply of medicines (guidance for pharmacies providing services at a distance). 4 February 2025. pharmacyregulation.org
  14. Wilding JPH et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). NEJM, 2021;384:989–1002. doi:10.1056/NEJMoa2032183
  15. Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). NEJM, 2022;387:205–16. doi:10.1056/NEJMoa2206038
  16. Aronne LJ et al. Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5). NEJM, 2025;393:26–36. Paid for by Eli Lilly, the maker of tirzepatide. doi:10.1056/NEJMoa2416394
  17. Davies M et al. Semaglutide 2·4 mg once a week in adults with overweight or obesity, and type 2 diabetes (STEP 2). Lancet, 2021;397:971–84. doi:10.1016/S0140-6736(21)00213-0
  18. MHRA. Yellow Card scheme: report a suspected side effect. yellowcard.mhra.gov.uk
  19. Wilding JPH et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. Diabetes, Obesity and Metabolism, 2022;24:1553–64. doi:10.1111/dom.14725
  20. Wilding JPH et al. Impact of semaglutide on body composition in adults with overweight or obesity: exploratory analysis of the STEP 1 study. Conference abstract, 2021. 140 people in a body-scan substudy of STEP 1. Abstract PDF
  21. Neeland IJ, Linge J, Birkenfeld AL. Changes in lean body mass with GLP-1-based therapies and mitigation strategies. Diabetes, Obesity and Metabolism, 2024;26 Suppl 4:16–27. doi:10.1111/dom.15728
  22. Kadowaki T et al. Semaglutide once a week in adults with overweight or obesity, with or without type 2 diabetes, in an east Asian population (STEP 6). Lancet Diabetes & Endocrinology, 2022;10:193–206. doi:10.1016/S2213-8587(22)00008-0
  23. Zhao L et al. Tirzepatide for weight reduction in Chinese adults with obesity (SURMOUNT-CN). JAMA, 2024;332:551–60. doi:10.1001/jama.2024.9217
  24. Kadowaki T et al. Efficacy and safety of once-weekly tirzepatide in Japanese patients with obesity disease (SURMOUNT-J). Lancet Diabetes & Endocrinology, 2025;13:384–96. doi:10.1016/S2213-8587(24)00377-2
  25. Caleyachetty R et al. Ethnicity-specific BMI cutoffs for obesity based on type 2 diabetes risk in England: a population-based cohort study. Lancet Diabetes Endocrinol 2021;9:419–26. doi:10.1016/S2213-8587(21)00088-7
  26. NICE. Overweight and obesity management (NG246), recommendation 1.9.11 (lower BMI thresholds for some ethnic groups). nice.org.uk
  27. NICE. Type 2 diabetes in adults: management (NG28), updated 18 February 2026. nice.org.uk
  28. Metformin hydrochloride prescribing information, US label (FDA), via DailyMed, September 2026. DailyMed
  29. Novo Nordisk. Ozempic (semaglutide) prescribing information, US label (FDA), June 2026. Not the UK label. DailyMed
  30. NHS. Gliclazide: medicine information page. Checked 12 October 2026. nhs.uk
  31. Novo Nordisk. Wegovy 2.4 mg FlexTouch, summary of product characteristics (UK label), sections 4.1–4.2. Date of revision 09/2026. emc
  32. MHRA. MHRA approves GLP-1 receptor agonist semaglutide to reduce risk of serious heart problems in obese or overweight adults. 23 July 2024. gov.uk
  33. MHRA. Semaglutide (Wegovy) approved to treat form of liver disease. 3 July 2026. gov.uk
  34. NICE. Tirzepatide for managing overweight and obesity (TA1026), 23 December 2024. nice.org.uk
  35. World Health Organization. WHO issues global guideline on the use of GLP-1 medicines in treating obesity. 1 December 2025. WHO
  36. Novo Nordisk. Ozempic, summary of product characteristics (UK label). Date of revision 07/2026. emc
  37. MHRA. MHRA authorises diabetes drug Mounjaro (tirzepatide) for weight management and weight loss. 8 November 2023. gov.uk
  38. MHRA Drug Safety Update. Falsified Mounjaro (tirzepatide) KwikPen 15 mg pre-filled pens. 24 February 2026. gov.uk
  39. MHRA. MHRA smashes major illicit weight loss medicine production facility in record seizure (Northampton). 24 October 2025. gov.uk
  40. Diabetes UK. Our response to serious supply issues of drugs for people living with type 2 diabetes (updated 20 October 2025). diabetes.org.uk
  41. Lincoff AM et al. Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). NEJM, 2023;389:2221–32. doi:10.1056/NEJMoa2307563
  42. NICE technology appraisal TA1152 (7 May 2026): semaglutide (Wegovy) to reduce the risk of heart attack, stroke and heart-related death in adults with established cardiovascular disease and a BMI of 27 or more; to be funded in England within 90 days. nice.org.uk
  43. US Food and Drug Administration. Byetta (exenatide) NDA 021773, approved 28 April 2005. 2005 label (FDA)
  44. Diabetes Times. Wegovy launches in the UK ("made available in the UK on Monday, September 4, 2023"). 5 September 2023. Trade press.
  45. MHRA. Single-dose 7.2 mg semaglutide (Wegovy) pen approved to treat adult patients with obesity (follows the January 2026 authorisation of the 7.2 mg weekly dose). 14 April 2026. gov.uk

Last checked 12 Oct 2026 · Next review due Jan 2027 · Report an error

How this guide was made. Written by the GLP Guidebook team from the sources above: published trials, UK and US drug labels, MHRA and NICE guidance and named reports. Where we cite a US label, we say so. It's general information, not medical advice. Talk to your GP or another qualified prescriber before starting, stopping or changing any medicine. In an emergency, call 999. For urgent help that isn't an emergency, use NHS 111 (in Northern Ireland, call your GP surgery for the out-of-hours service). Report suspected side effects to the Yellow Card scheme. How we write