For those who meet the eligibility criteria, Wegovy is considered a safe weight loss medication and is approved by trusted regulators like the MHRA in the UK, as well as regulators across the world. Like any medicine, it can cause side effects, most often mild ones like nausea, diarrhoea, vomiting, or constipation, which usually ease as your body adjusts. [1] 

More serious reactions are rare, and your prescriber will make sure it’s the right fit for you based on your health and any other medicines you take. If you’re thinking about starting Wegovy, it’s worth understanding both its benefits and possible risks — we’ve covered them in detail below so you can make an informed choice.

What is Wegovy?

Wegovy is a weight loss medication that comes in an injection pen that you use once a week. The main ingredient is called semaglutide. Each pen has a different amount of medicine: you start with a lower dose and slowly increase it over time. [1] The medicine has been approved by health authorities across the world, including the UK for weight management. You inject it under your skin, usually in your tummy, thigh, or upper arm once a week.

How Wegovy works in your body

Wegovy works by copying a hormone that your body makes naturally, called glucagon-like peptide-1 (GLP-1). The main ingredient, semaglutide, sends a signal to your brain mimicking GLP-1 to say you’re full, even when you haven’t eaten much. [2] In technical terms, this makes it a GLP-1 receptor agonist. 

The medicine works in these main ways: it makes you feel less hungry, it makes you feel full for longer after eating, and it keeps your blood sugar steady which reduces cravings. It also works on the area of your brain that controls appetite, so it can help reduce ‘food noise’, or constantly thinking about eating and food. [1] All of this can help you eat less and in doing so, lose weight. [2]

Wegovy vs Ozempic and Mounjaro

Wegovy vs Ozempic 

You might’ve heard of Ozempic, which also contains the ingredient semaglutide. The main difference is that Ozempic is prescribed for people with diabetes, while Wegovy is specifically for weight loss.

In the UK, doctors can prescribe both medicines, but they’ll prescribe them for different reasons — Ozempic is for diabetes and Wegovy is for weight management in adults who are significantly overweight. 

Like all medicines, both can cause side effects, especially when you first start taking them. These side effects usually get better as your body gets used to the medicine, and this is why it’s important to start with a slow dose and gradually increase it. Your prescriber will check that these medicines are safe for you before prescribing them.

Wegovy vs Mounjaro

Mounjaro is a weight loss injection that works similarly to Wegovy, but has a different active main ingredient called tirzepatide. There are similarities and differences between Mounjaro and Wegovy: both are weekly injections that help you feel less hungry and lose weight.

The main difference is that Mounjaro mimics two different hormones in your body (GLP-1 and gastric inhibitory peptide, or GIP), while Wegovy mimics just one (GLP-1). Both medicines need to be prescribed and need to be combined with healthy eating and exercise. Your prescriber can help you decide which one might be better for you based on your health and other medicines you take.

In terms of their safety profiles, Wegovy and Mounjaro are both licensed for use for weight management in the UK by the MHRA (Medicines and Healthcare products Regulatory Agency). A clinical study found that there was no significant difference between the medications in terms of their gastrointestinal side effects. [3] 

How safe is Wegovy?

When looking at Wegovy’s safety profile, one of the main indicators that it’s safe is the fact that it’s approved by the MHRA in the UK (as well as by medicine regulators across the world). There has to be a strong evidence base around its safety for the medication to be approved by these bodies. 

These medicine regulators only approve medications after carefully checking that they work as the medicine manufacturers claim and that their benefits outweigh any risks. 

To understand if Wegovy is safe for you, it’s important to understand both its benefits and side effects. While most people only experience mild side effects like feeling sick, there’s a small chance of more serious side effects, though this is uncommon. [1]

The best thing you can do is learn as much as you can about its safety and ask lots of questions if you’re not sure about something. We’re here to help you understand everything you need to know about Wegovy’s safety profile, so you can make an informed choice about whether, if you’re eligible, taking Wegovy is right for you.

Health benefits of Wegovy

Better heart health

One of the most exciting discoveries about Wegovy is that it benefits your cardiovascular health, that is to say your heart health. A big study called a SELECT study found that people taking 2.4mg of semaglutide, the highest dose, had fewer cardiovascular events — that means fewer heart attacks and strokes. [4]

The benefit to your heart seems to happen even beyond what you’d expect from just losing weight. Semaglutide appears to directly protect your heart and blood vessels, lower blood pressure, and improve cholesterol levels. [4]

Other health improvements

When people lose weight with Wegovy, they often see improvements in other health problems too. Sleep apnoea (when breathing stops during sleep) often gets better. [5] Joint pain and mobility can improve because there’s less weight putting pressure on joints. [6]

Many people also see improvements in blood sugar levels, even if they don’t have diabetes. This can help prevent type 2 diabetes from developing. [7] Some studies suggest semaglutide might help with fatty liver disease, too. [8, 9]

How effective is Wegovy for losing weight?

A large clinical trial  called a STEP study showed that people taking semaglutide lost an average of around 15% of their body weight over 68 weeks. [10] A long-term study that ran for two years, showed that people taking semaglutide lost an average of 15% of their body weight over two years. [11]

This means that if someone weighed 100kg at the start, they would typically lose about 15kg. Most people saw good results — more than 3 out of 4 people (77%) lost at least 5% of their starting weight, and nearly half (44%) lost 10% or more of what they weighed when they began treatment. [11]

However, one study showed that 12% of people who stopped taking semaglutide regained weight after a year [12], and another study found that people who stopped taking semaglutide regained 7% of their weight in 20 weeks [13]. 

This suggests that Wegovy is effective for helping people lose weight, but keeping the weight off after stopping the medication requires continued positive lifestyle changes such as physical activity and a healthy diet. More research is needed to understand how to make sure your new weight is maintained after stopping the medication.

Side effects and safety concerns

Common side effects

Most people who take Wegovy experience some side effects, especially when they first start or when their dose is increased. The most common are nausea, diarrhea and constipation. [1]

Of those taking the maximum dose of semaglutide (2.4mg), 44% had nausea, 30% had diarrhea, 25% had vomiting, and 24% had constipation. [14] The good news is that these problems usually get better after a few weeks as your body gets used to the medicine. [1]

Some people get redness or soreness where they inject the medicine, but this is usually mild and goes away quickly. [1] This is why it is important to rotate injection sites every time you use the pen, and why it is important to know how to use the Wegovy pen safely. 

Serious side effects to watch out for

While most side effects are manageable, there are some serious ones, though they’re uncommon. One is inflammation of the pancreas (called pancreatitis), which may affect up to 0.2% people taking Wegovy. [1] Signs include severe stomach pain that doesn’t go away, being sick, and fever. It is important to get emergency medical help if you notice these severe symptoms.

Rare but very serious reactions include a severe allergic reaction, called anaphylaxis. This may occur in up to 1 in 1,000 people, and although unlikely it is important to know the signs and get emergency help immediately. Signs include difficulty breathing, swelling of your face, lips, tongue, and/or throat, wheezing, a fast heartbeat, pale and cold skin, and feeling dizzy or weak. [1]

Long-term safety questions

Because Wegovy is a relatively new weight loss medication, doctors and researchers are still learning about long-term effects. In safety studies, semaglutide could cause thyroid tumours, so there’s a warning about a rare type of thyroid cancer called medullary thyroid carcinoma.  Therefore, people with a family history of this type of thyroid cancer, or a condition called Multiple Endocrine Neoplasia syndrome type 2, shouldn’t take Wegovy. [1]

Safety concerns for certain groups

Pregnant people must not take Wegovy because some safety studies have shown it can cause birth defects in babies. If you’re planning to get pregnant, it’s important to stop taking Wegovy at least 2 months before trying to conceive because the medicine can stay in your system for a long time.

Taking Wegovy while breastfeeding or chestfeeding is not advised. If you can get pregnant, you need to use reliable contraception while taking Wegovy. Wegovy doesn’t affect how well the contraceptive pill works. [1]

Wegovy doesn’t increase the risk of depression or thoughts of suicide in most people. However, some studies suggest there might be a small increase in suicidal thoughts for people who already have anxiety or depression. [15, 16] If you have depression or anxiety, it’s important to talk to your doctor about this before starting treatment so you get the support you need.

Getting Wegovy in the UK

Am I eligible for Wegovy?

Wegovy is for adults who are obese (body mass index of 30 or higher) or overweight (body mass index of 27 or higher) with weight-related health problems. Weight-related health problems include high blood pressure, type 2 diabetes, high cholesterol, or heart disease.

You also need to be willing to make changes to your diet and exercise habits. Wegovy works best when combined with a healthy diet, including lean protein and fibre, and regular physical activity — it’s not a magic solution on its own. 

NHS availability

Getting Wegovy on the NHS is restricted at the moment. The National Institute of Clinical Excellence (NICE) guidelines around Wegovy prescription are strict and you usually need to have tried other weight loss methods first and meet specific criteria. You need a referral to NHS specialist weight management services, who can then assess and support you with options for weight loss. 

To get Wegovy on the NHS your BMI needs to be 35 or higher with a weight-related health condition, or in some exceptional cases 30 or higher with other weight-related health problems, like high blood pressure or heart disease. 

This is more restricted than the eligibility for Wegovy’s license, that is what medicine regulators approve its use for, which is generally a BMI of 30 or of 27 with weight-related health conditions.

There are often waiting lists for NHS weight loss services, and availability varies across different areas of the UK. Your GP can refer you to specialist weight management services if you meet the NHS criteria.

The NHS considers the cost of Wegovy when deciding who can have it, so they focus on people who are most likely to benefit and who have tried other approaches first.

Private options

You can access Wegovy privately through some doctors and trusted online providers, such as MedExpress. This can mean faster access to treatment, with the added convenience of expert care from your home.

Online services make it simpler to connect with experienced weight loss specialists, which is especially helpful if you don’t have local options nearby. Our team ensures you receive proper care and ongoing check-ins, so your treatment is safe and tailored to you.

 Find out what treatment is suitable for you on our website.

Final consideration: Is Wegovy safe for you?

Deciding whether Wegovy is safe for you depends on many factors including your health and other medicines you take. For many people who are significantly overweight, the benefits can outweigh the risks.

If you’re considering Wegovy, have an honest consultation with your GP or an experienced online provider like MedExpress about your health history, current medicines, and what you hope to achieve. Your prescriber can help you weigh up the benefits and risks and help decide if it’s the right choice for you.

References

1. Medicines.org.uk. Wegovy 0.25 mg, FlexTouch solution for injection in pre-filled pen – Summary of Product Characteristics (SmPC) – (emc) [Internet]. [place unknown]: Medicines.org.uk; [cited 2025 Aug 12]. Available from: https://www.medicines.org.uk/emc/product/13799/smpc#gref
   
2. Blundell J, Finlayson G, Axelsen M, Flint A, Gibbons C, Kvist T, Hjerpsted JB. Effects of once‐weekly semaglutide on appetite, energy intake, control of eating, food preference and body weight in subjects with obesity. Diabetes Obes Metab. 2017;19(9):1242–51. doi:10.1111/dom.12932.
   
3. Rodriguez PJ, Goodwin Cartwright BM, Gratzl S, Brar R, Baker C, Gluckman TJ, Stucky NL. Semaglutide vs Tirzepatide for weight loss in adults with overweight or obesity. JAMA Intern Med. 2024;184(9). doi:10.1001/jamainternmed.2024.2525.
   
4. Lincoff AM, Brown‐Frandsen K, Colhoun HM, Deanfield J, Emerson SS, Esbjerg MS, Hardt‐Lindberg S, Hovingh GK, Kahn SE, Kushner RF, Lingvay I, Oral TK, Michelsen MM, Plutzky J, Tornøe CW, Ryan DH. Semaglutide and cardiovascular outcomes in obesity without diabetes. N Engl J Med. 2023;389(24). doi:10.1056/NEJMoa2307563.
   
5. Le R, Le K, Foo F. The impact of glucagon-like peptide 1 receptor agonists on obstructive sleep apnoea: a scoping review. Pharmacy (Basel). 2024;12(1). doi:10.3390/pharmacy12010011.
   
6. Bliddal H, Bays H, Czernichow S, Uddén Hemmingsson J, Hjelmesæth J, Hoffmann Morville T, Koroleva A, Skov Neergaard J, Vélez Sánchez P, Wharton S, Wizert A, Kristensen LE. Once-weekly semaglutide in persons with obesity and knee osteoarthritis. N Engl J Med. 2024;391(17):1573–83. doi:10.1056/NEJMoa2403664.
   
7. Perreault L, Davies M, Frias JP, Laursen PN, Lingvay I, Machineni S, Varbo A, Wilding JPH, Wallenstein SOR, le Roux CW. Changes in glucose metabolism and glycemic status with once-weekly subcutaneous semaglutide 2.4 mg among participants with prediabetes in the STEP program. Diabetes Care. 2022;45(10). doi:10.2337/dc21-1785.
   
8. Sanyal AJ, Newsome PN, Kliers I, Østergaard LH, Long MT, Kjær MS, Cali AMG, Bugianesi E, Rinella ME, Roden M, Ratziu V. Phase 3 trial of semaglutide in metabolic dysfunction–associated steatohepatitis. N Engl J Med. 2025;392(21). doi:10.1056/NEJMoa2413258.
   
9. Loomba R, Abdelmalek MF, Armstrong M, Jara M, Kjaer M, Krarup N, Lawitz E, Ratziu V, Sanyal AJ, Schattenberg JM, Newsome P. Semaglutide 2.4 mg once weekly in patients with non-alcoholic steatohepatitis-related cirrhosis: a randomised, placebo-controlled phase 2 trial. Lancet Gastroenterol Hepatol. 2023;8(6):511–22. doi:10.1016/S2468-1253(23)00068-7.
   
10. Wilding JPH, Batterham RL, Calanna S. Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med. 2021;384(11):989–1002. doi:10.1056/NEJMoa2032183.
    
11. Garvey WT, Batterham RL, Bhatta M, Buscemi S, Christensen LN, Frias JP, Jódar E, Kandler K, Rigas G, Wadden TA, Wharton S. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nat Med. 2022;28(10):2083–91. doi:10.1038/s41591-022-02026-4.
    
12. Wilding JPH. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. Diabetes Obes Metab. 2022;24(8):1553–64. doi:10.1111/dom.14725.
    
13. Rubino D, Abrahamsson N, Davies M, Hesse D, Greenway FL, Jensen C, Lingvay I, Mosenzon O, Rosenstock J, Rubio MA, Rudofsky G, Tadayon S, Wadden TA, Dicker D. Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance in adults with overweight or obesity: the STEP 4 randomized clinical trial. JAMA. 2021;325(14):1414–25. doi:10.1001/jama.2021.3224.
    
14. Wharton S, Calanna S, Davies M, Dicker D, Goldman B, Lingvay I, Mosenzon O, Rubino DM, Thomsen M, Wadden TA, Pedersen SD. Gastrointestinal tolerability of once‐weekly semaglutide 2.4 mg in adults with overweight or obesity, and the relationship between gastrointestinal adverse events and weight loss. Diabetes Obes Metab. 2024;24(1). doi:10.1111/dom.14551.
    
15. Wadden TA, Brown GK, Egebjerg C, Frenkel O, Goldman B, Kushner RF, McGowan B, Overvad M, Fink-Jensen A. Psychiatric safety of semaglutide for weight management in people without known major psychopathology. JAMA Intern Med. 2024. doi:10.1001/jamainternmed.2024.4346.
    
16. Schoretsanitis G, Weiler S, Barbui C, Raschi E, Gastaldon C. Disproportionality analysis from World Health Organization data on semaglutide, liraglutide, and suicidality. JAMA Netw Open. 2024;7(8):e2423385. doi:10.1001/jamanetworkopen.2024.23385.