Should I consider a GLP-1 medicine? And when not to

What do doctors look at?

Doctors look at your weight, your health conditions, and what you've already tried. A BMI number alone does not decide it.

BMI (body mass index) is your weight in kilograms divided by your height in metres squared. Two different sets of numbers get mixed up online. One set describes your weight. The other is where a doctor may start to think about medicine. They are not the same thing.

Type 2 diabetes is a separate reason. Ozempic is licensed in the UK to control blood sugar in type 2 diabetes. That licence has no weight cut-off.¹ NICE's diabetes guidance, updated in February 2026, says doctors should consider adding a GLP-1 medicine or tirzepatide for people living with obesity, once they have been on their first diabetes medicines for at least 3 months.²⁰ Your doctor will look at your HbA1c (a blood test of your average sugar level over about 3 months) and your other medicines.

Other licensed uses exist. In July 2024, the MHRA approved Wegovy to lower the risk of serious heart problems in adults with heart disease and excess weight.¹⁸ In July 2026, it approved Wegovy for a type of fatty liver disease that has caused scarring in the liver (MASH).¹⁹

Who can prescribe. On the NHS, it's your GP or a specialist service, depending on the medicine and where you live (next section). Privately, a registered prescriber can prescribe within the licence, including through an online pharmacy. Online services must check your weight by video, in person or from your records.³¹ Guide 6 explains both routes.

Who can get one on the NHS?

Far fewer people than the licence covers. The NHS opens access in stages, and each of the four nations has its own rules.

England: Mounjaro through your GP, in stages

NICE recommends Mounjaro (tirzepatide) for adults with a BMI of 35 or more and at least one weight-related condition.¹⁰ Because so many people fit that, the NHS is allowed to roll it out over up to 12 years. In the first 3 years, about 220,000 people should become eligible.¹⁰ The groups open in this order:¹⁰

• From June 2025BMI 40 or more, and 4 or more of the 5 conditions below.
• From about June 2026BMI 35 to 39.9, and 4 or more of the conditions.
• From about March 2027BMI 40 or more, and 3 of the conditions.

The 5 conditions are high blood pressure, abnormal blood fats (cholesterol), obstructive sleep apnoea (breathing that stops and starts in sleep), heart and blood-vessel disease, and type 2 diabetes.¹⁰ For people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds, the BMI numbers are 2.5 lower: for example, 37.5 instead of 40.^10,2

Some local NHS areas say they will contact eligible patients directly, and ask people not to book GP appointments about it unless invited.¹⁶ Check what your own area says.

England: Wegovy and Saxenda through a specialist service

For weight, NICE recommends Wegovy (semaglutide) only within a specialist weight management service, for up to 2 years.¹¹ You need at least one weight-related condition and a BMI of 35 or more, or 30 to 34.9 if you meet the service's referral criteria. The numbers are lower for the same ethnic groups.¹¹ Saxenda (liraglutide) is also for specialist services, for a narrower group with raised blood sugar and high heart risk.³⁰ You cannot get either for weight through your GP practice.¹¹

A newer route for heart disease. In May 2026, NICE recommended Wegovy to lower the risk of heart attack and stroke in adults who already have heart or circulation disease (a past heart attack, stroke, or symptomatic peripheral arterial disease) and a BMI of 27 or more. It does not say which service should prescribe it.¹²

NHS rules are changing fast. Checked 12 Oct 2026.

Who should not take a GLP-1?

Some people should never take these medicines. Others need extra care, and a doctor may decide it isn't safe for them.

Every label rules out anyone with a serious allergy to the medicine.^3,8,9 The US labels add a second group: anyone with a personal or family history of medullary thyroid cancer (MTC), or a rare inherited condition called MEN2 (multiple endocrine neoplasia type 2).^3,6 The UK labels don't list it as a reason not to take the medicine, but tell your doctor if it applies to you.^8,9

The thyroid warning comes from animal studies. Semaglutide caused thyroid tumours in rodents. Nobody knows yet whether it does the same in people.³

The table below lists the main conditions. "Do not take" means the label lists it as a firm reason not to use the medicine. "Not recommended" means the label advises against it. "Caution" means a doctor may still prescribe, but watches you more closely. "Tell your doctor" means the US labels list it as a reason not to take the medicine, but the UK labels don't.

From the US Wegovy and Zepbound labels, the European Wegovy label and the MHRA's patient guidance. Your own pack leaflet is the UK version; read it before you start.

What about pregnancy, PCOS and the pill?

Don't take a GLP-1 while pregnant. If you could get pregnant, plan contraception with your doctor before you start.

These medicines stay in the body for a while after the last dose. So the MHRA says to stop them before trying to get pregnant: at least 2 months before for semaglutide (Wegovy, Ozempic), and at least 1 month before for tirzepatide (Mounjaro).¹ The European Mounjaro label gives the same 1 month.⁷

Tirzepatide can make the contraceptive pill less reliable. It slows the stomach, which can affect how well the pill is absorbed. The effect is largest after the first dose.⁶

If you take the pill with Mounjaro, the MHRA advises adding a barrier method, such as a condom, for 4 weeks after starting and for 4 weeks after each dose increase.¹ Methods that aren't swallowed, like a hormonal coil (IUS), are not affected.⁶

Semaglutide is not expected to make the pill less effective, according to its European label.⁴

Teens, older adults, kidneys, liver, other medicines and surgery

These groups can sometimes use GLP-1 medicines. But each one needs extra checks, and some need a specialist.

Teenagers

In the UK, Wegovy is licensed for weight management from age 12, for teens with obesity who weigh over 60 kg (9 st 6 lb), alongside diet and activity.⁸ The European label says to stop and rethink if a teen's BMI hasn't dropped by at least 5% after 12 weeks on the full dose.⁴ Gallstones were more common in teens than adults on Wegovy.³ Mounjaro's UK licence for weight is for adults only.⁹

Older adults

Older people can lose muscle along with fat, which raises the risk of frailty. Direct evidence in older adults is scarce.²⁹ In a large Wegovy trial, people aged 75 and over had more hip and pelvis fractures than on a dummy injection.³ Dehydration from vomiting or diarrhoea can harm the kidneys, so drinking enough matters.³

Kidney disease

Kidney injury has been reported, mostly in people who got dehydrated from stomach side effects.³ The European label does not recommend Wegovy if kidney function is very low (an eGFR blood-test result below 30).⁴ But in people with type 2 diabetes and kidney disease, Ozempic is approved in the US to help protect the kidneys.⁵ So this is a decision for your kidney or diabetes doctor.

Liver disease

The MHRA approved Wegovy in July 2026 for a type of fatty liver disease with scarring (MASH).¹⁹ It is not recommended in severe liver impairment, and needs caution in milder cases.⁴

If you take insulin or a sulfonylurea

Sulfonylureas are diabetes tablets like gliclazide and glimepiride. Taken with a GLP-1, they and insulin raise the risk of low blood sugar (a hypo), including severe hypos.³ Your doctor may lower their dose when you start, and should explain the signs of a hypo.³

Before surgery or an endoscopy (camera test)

GLP-1 medicines slow your stomach. Rarely, food has stayed in the stomach despite fasting, and been breathed into the lungs under anaesthetic.³ Always tell the surgeon and anaesthetist you take one.³

US guidance from 2024 says most people can keep taking it before planned surgery. Higher-risk people may need a liquid-only diet for 24 hours first. That includes people in the early dose-increase weeks, on higher doses, or with stomach symptoms.²⁵ Your UK hospital team may have its own advice; follow theirs.

What if I only want to lose a few pounds?

These medicines are not meant for a few pounds before a wedding or a holiday, or for losing fat for bodybuilding. You'd take on the same risks with no proven benefit.

It's not what they are licensed for. The weight licences cover obesity, or overweight with a weight-related condition.^8,9 The MHRA says not to use them for cosmetic reasons.¹ The big trials only included people with obesity or overweight with a condition.^21,22

The risks don't shrink because your goal is small. Stomach side effects, gallstones and pancreatitis can still happen.³

The weight tends to come back. A year after stopping semaglutide, people had regained about two-thirds of what they'd lost.²⁴ A short course before an event is likely to be undone afterwards.

Some of what you lose is muscle. In studies, muscle made up as much as a quarter of the weight lost.²⁹ That works against a gym goal.

Fakes are a real risk in the UK. The MHRA has found fake Ozempic and Saxenda pens here.²⁶ In February 2026, it warned that a fake Mounjaro 15 mg pen had been supplied through one UK online pharmacy.²⁷ It also says products sold as a powder in a vial, to be mixed before injecting, are not authorised.¹

What results can I honestly expect?

Most people in trials lost a meaningful amount of weight. But results vary a lot, side effects are common, and the weight returns if you stop.

Before the numbers, how these trials work:

• People are put into groups at random.
• One group gets the medicine. The other gets a dummy injection (a placebo) that looks the same but has no medicine in it.
• Both groups get the same advice on diet and activity.
• The gap between the groups is what the medicine added.

Trials use losing 5% of body weight as a key marker.^21,22 For someone who starts at 90 kg (14 st 2 lb), that's 4.5 kg (about 10 lb). Out of every 100 people in each trial, this is how many reached it:

These are separate trials with different people, so they can't be compared with each other.

Put the other way, about 1 in 7 people on semaglutide and 1 in 11 on tirzepatide lost less than 5%. With type 2 diabetes, it was nearly 1 in 3.^21,22,23

Side effects make some people stop. In the semaglutide trial, 4.5 in 100 people quit because of stomach side effects, against 0.8 in 100 on the dummy. This count includes only stomach side effects.²¹ On tirzepatide 15 mg, 6.2 in 100 stopped because of any side effect, against 2.6 in 100.²² So the two numbers measure different things.

People with diabetes tend to lose less. The average was 9.6% of body weight in the diabetes trial, against 14.9% in people without diabetes.^23,21

Expect a check at 6 months. NICE says to consider stopping Wegovy if you have lost less than 5% of your starting weight after 6 months.¹¹ For Mounjaro, it says that if you've lost less than 5% after 6 months on the highest dose you can tolerate, you and your doctor decide whether to carry on.¹⁰

Think of it as long-term. The study on stopping concluded that ongoing treatment seems needed to keep the benefits.²⁴ On the NHS in England, Wegovy for weight is limited to 2 years in a specialist service.¹¹ Guide 9 covers stopping.

Cost adds up if you pay privately. Guide 6 explains NHS prescription charges in each nation and the official list prices.

A way to think it through

Use this to sort your thoughts before a doctor visit. It does not give you a yes. Only a doctor who knows your health can.

Questions to ask yourself

There's no score here. These questions help you know what you want, and what you're ready for.

• Why do I want this now? Is it my health, or pressure from others?
• What have I tried before? What worked, even for a while?
• Could I keep taking a medicine for years, not months?
• Do I fit an NHS route where I live? If not, could I pay privately for a year or more?
• How would I cope with feeling sick or having an upset stomach for a few weeks?
• Am I planning a pregnancy in the next year or two?
• Have I ever struggled with an eating disorder, like bingeing or starving myself?
• Who will support me with food changes and activity?

What should I bring to the doctor?

Bring your history, your medicines and any recent test results. Then ask the questions below. You can print this card.

On the NHS, your GP is usually the first step, but check your local area's advice before booking about Mounjaro. See the NHS routes, above. Guide 6 explains NHS and private prescriptions, and the checks an online pharmacy must make.

What support comes with it?

On the NHS in England, Mounjaro comes with a support programme on food and activity, and you have to take part.

Local NHS guidance says anyone prescribed Mounjaro must join the "wraparound" care that NICE requires, which focuses on diet, nutrition and more activity. You cannot be prescribed it on the NHS if you don't want that support.^17,10

Whatever route you take, it helps if someone at home knows what you're taking, which side effects to expect, and when to get help.

Questions people ask