What is Semaglutide and is it safe for weight loss?

Dr Crystal Wyllie

Medically reviewed by

Dr Crystal Wyllie

Last reviewed: 10 Jan 2024

Semaglutide is a prescription-only medicine licensed for weight loss in the UK. It is available in the form of semaglutide injections that are used once weekly alongside diet and exercise changes to promote weight loss in overweight individuals. Semaglutide works by suppressing your appetite, making you feel fuller for longer. It is currently available under the brand name Wegovy.

Light grey semaglutide injection pen for weight loss, branded for Wegovy®

What is semaglutide used for?

Semaglutide injections are used to control blood sugar levels in adults with type 2 diabetes but they are also available as a weight loss treatment under the brand name Wegovy. Semaglutide works by making you feel less hungry, and when used alongside other lifestyle changes can help you to lose weight. Semaglutide for weight loss is taken once per week and is only available on prescription.

Is semaglutide available in the UK?

Yes, semaglutide is available in the UK for weight loss under its brand name. The semaglutide brand name is Wegovy, so your doctor may refer to the semaglutide injections as ‘Wegovy’ injections.

Semaglutide is also available as an injection called Ozempic and as tablets under the brand name Rybelsus. Rybelsus and Ozempic are not licensed for weight loss treatment. Instead, they are prescribed for type 2 diabetes for patients who need to lower their blood glucose levels.

Is semaglutide insulin?

“Semaglutide is not insulin. It is used for the treatment of type 2 diabetes and more recently weight loss. It works by mimicking the hormone glucagon-like peptide-1 (GLP-1) that’s released in response to eating. It works by prompting your body to produce more insulin to lower blood sugar levels.” – Dr Crystal Wyllie, Doctor at ZAVA.

What does semaglutide do to your body?

Semaglutide is used to control blood sugar levels in type 2 diabetes and to aid weight loss in obese individuals. It works by imitating the GLP-1 hormone that is released by your gut in response to eating. So, semaglutide reduces your appetite, telling your brain that you feel full, similar to what the GLP-1 hormone naturally does after you eat a meal.

By working in this way, semaglutide helps to keep you feeling fuller for longer and helps you avoid overeating, reducing your calorie intake. This results in weight loss and enables you to keep to a diet plan.

How does semaglutide work for weight loss?

Semaglutide injections for weight loss work by suppressing your appetite, making you eat less to lose weight. They must be used alongside exercise and a low-calorie diet program for effective long-term weight management.

How long does semaglutide take to work?

Semaglutide starts to work after your first dose but it can take several weeks or months before you notice any effects. If you have not noticed any significant weight loss after 6 months of using semaglutide, you should consider changing your treatment.

How effective is semaglutide for weight loss?

Although there are several weight loss medications available, semaglutide has shown promising early results. For example, an early study published in the New England Journal of Medicine in 2021 involving 1,961 adults, demonstrated that after 68 weeks of weekly semaglutide injections plus a diet and exercise program, 612 participants achieved 15% weight loss and almost one third achieved 20% weight loss.

A further 2022 cohort study involving 175 overweight or obese patients investigated the effectiveness of semaglutide and found that total body weight loss was 5.9% at 3 months and 10.9% at 6 months. These results confirm that weight loss outcomes in this small study were similar to those achieved in randomised clinical trials.

A systematic review which included 8 studies involving a total of 4,567 patients concluded that semaglutide not only resulted in significant weight loss but was also safe for obese and overweight individuals without diabetes.

How much weight can you lose in a month with semaglutide?

It is difficult to quantify how much weight you can lose in a month while using semaglutide because everyone is individual and our bodies will react in different ways. However, research has shown that after 68 weeks of semaglutide injections, 86% of people lose at least 5% in weight.

Are semaglutide injections safe for weight loss?

Semaglutide injections are safe for weight loss for people who meet specific criteria. Like all medicines, semaglutide can cause side effects, but these should subside once your body has gotten used to the new medication.

What do you feel after taking semaglutide?

Some people report feeling sick (nausea), being sick (vomiting) or having diarrhoea when they first start using semaglutide injections for weight loss. The semaglutide dosing schedule is intended to lower the risk of experiencing these side effects, but people who do experience them often report that they go away after a few weeks of using the medication.

If you take semaglutide and are unable to tolerate the side effects, then you may need to discuss an alternative treatment with your doctor.

Can normal people take semaglutide?

Semaglutide injections are not intended for healthy people or those who are not diabetic or obese. Semaglutide is not intended to be used by anyone who is looking to lose a small amount of weight or who does not fit the specified criteria.

Can I take semaglutide if I’m not obese?

No, doctors can only prescribe semaglutide weight loss injections to people who have a BMI of 30 or more or a BMI between 27 and 30 if they have a weight-related health issue.

What happens when you stop taking semaglutide?

When you stop taking semaglutide for weight loss, you can regain the weight you have lost. For example, one study found that 52 weeks after stopping once-weekly semaglutide injections, participants regained 66% of their prior weight loss. That’s because when you stop the medication, you will regain your appetite which can increase your calorie intake and lead to you putting the weight back on. If you also have type 2 diabetes, it can also mean your blood sugar levels may rise, increasing your risk of diabetes-associated adverse health effects.

How much does semaglutide cost?

The semaglutide cost will depend on where you get your prescription from. If you are eligible for semaglutide on the NHS, you may be subject to prescription charges.

Semaglutide injections are also available on a private prescription from ZAVA. The current semaglutide costs start at £179.00. Semaglutide is available under its brand name Wegovy online, as there is currently no cheaper generic version available.

Is semaglutide safe for non-diabetics?

Originally, semaglutide for diabetes was prescribed to lower blood sugar levels in diabetic patients. However, while using semaglutide, it was found that some patients were also losing weight, leading to it being licensed for weight loss in the UK.

People who are overweight or obese are at a higher risk of developing type 2 diabetes. But not everyone who is overweight or obese does become diabetic. So, it is safe for doctors to prescribe semaglutide for weight loss in non-diabetics.

Semaglutide side effects

Semaglutide side effects include:

Very common

  • Feeling sick (nausea)
  • Being sick (vomiting)
  • Diarrhoea
  • Constipation
  • Headache
  • Stomach pain
  • Feeling tired or weak


  • Dizziness
  • Upset stomach
  • Indigestion
  • Bloating
  • Gas
  • Stomach inflammation (gastritis)
  • Acid reflux
  • Heartburn
  • Gallstones
  • Hair loss
  • Low blood sugar (hypoglycaemia)
  • Injection site reactions


  • Increased heartburn
  • Increase in pancreatic enzymes
  • Delayed emptying of the stomach

For further information about semaglutide side effects, please refer to the Wegovy patient information leaflet.

Semaglutide contraindications

Semaglutide is not suitable for everyone and you should only take it if your doctor agrees it is safe for you to do so.

Semaglutide for weight loss should only be used if you are overweight and have a BMI of 30 or more, or over 27 if you have a weight-related health problem. A doctor cannot prescribe semaglutide injections for weight loss if you are not clinically overweight, even if you are looking to lose weight.

As well as meeting the above criteria, semaglutide may not be suitable for you if you are:

  • Pregnant or planning to get pregnant
  • Allergic to any of the ingredients in semaglutide injections or tablets for weight loss

Before prescribing semaglutide, your doctor may also ask if you have:

  • Kidney problems
  • An inflamed pancreas
  • Diabetes
  • Low blood sugar levels
  • Diabetic eye disease (retinopathy)

Why is semaglutide contraindicated in pregnancy?

Semaglutide is not recommended for pregnant women or women who are trying to get pregnant because animal studies have shown that it may cause birth defects, miscarriage, or stillbirth. There are currently no human studies available about the effects semaglutide may have on human pregnancy. This isn’t unusual as it is not ethical to test medicines on pregnant people, but semaglutide is not recommended to be used by pregnant women. If you are worried, you should speak to your doctor for advice.

What are the risks of semaglutide?

Semaglutide may cause serious side effects, such as:

  • Thyroid tumours. You should let your doctor know immediately if you notice any lumps or swelling in your neck, have trouble swallowing or breathing, or experience a hoarse voice. The symptoms could indicate thyroid cancer.
  • Inflamed pancreas. If you experience severe pain in your stomach that doesn’t go away with or without vomiting you should seek medical advice straight away.
  • Gallbladder problems. Gallbladder problems include gallstones and you may experience pain in your upper tummy area, fever, yellowing of the skin or the whites of your eyes (jaundice), or clay-coloured stools.
  • Kidney problems. Some of the side effects associated with semaglutide like feeling or being sick and diarrhoea can increase loss of fluids which can make existing kidney issues worse.
  • Depression. You should inform your doctor if you experience any mental health changes while taking semaglutide, especially in your mood, behaviour, thoughts, or feelings.
  • Increased heart rate. Tell your doctor if you feel your heart racing or pounding, especially when at rest while using semaglutide.

Can you get semaglutide without a doctor?

To get semaglutide you will need a semaglutide prescription from a doctor. It cannot be bought over the counter at a pharmacy or supermarket and can only be prescribed to suitable patients who meet strict criteria.

You do not necessarily need to see a doctor face to face to get semaglutide, though. Services like ZAVA can prescribe semaglutide to suitable people using their online service.

Is semaglutide available on the NHS for weight loss?

Yes, semaglutide injections for weight loss are available on the NHS as a weight loss treatment option. They have been made available in line with guidelines from the National Institute for Health and Care Excellence (NICE).

NICE recommends that semaglutide injections be prescribed alongside a reduced-calorie diet and increased exercise. A doctor may recommend using semaglutide for weight loss if diet or exercise changes alone have not worked.

Conclusion: Is semaglutide a good drug for weight loss?

Clinical trials show that semaglutide delivers promising results for weight loss. After 68 weeks of using semaglutide injections, 86% of patients achieved at least 5% weight loss and 32% recorded 20% weight loss in the same period. Whether semaglutide is the right medicine for you will depend on a variety of factors, including whether you meet the criteria for treatment and are happy to commit to a diet and exercise plan alongside the medication.

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Frequently asked questions

Can you lose weight on semaglutide without changing your diet?

Semaglutide does not result in weight loss by itself. It is recommended that you follow a restricted-calorie diet and increase your exercise output while taking semaglutide to achieve the full benefits of the medication.

What happens if I miss a week of semaglutide?

If you miss your dose of semaglutide and it is within 5 days from your last dose, you should take it as soon as you remember. Then inject your next dose as usual.

If it has been more than 5 days since you should have used semaglutide, you will need to skip your missed dose. Then inject your next dose as usual on your next scheduled day. Never make up for a missed dose by taking a double dose.

Can semaglutide cause hair loss?

Hair loss is listed as a potential side effect of semaglutide, including Wegovy and Ozempic, but it is rare. Some people can experience temporary hair loss when they lose weight, but it usually only lasts for about 6 months. If you are concerned about hair loss and semaglutide, speak to your doctor.

How do you know if semaglutide is working?

It can take weeks or months for you to notice any benefits for weight loss while using semaglutide. If you have diabetes, you may notice your blood sugar levels lowering after 2 weeks. If you do not notice any effects after 6 months, you should consider discussing alternative weight loss interventions with your doctor.

Can I take semaglutide if I am not diabetic?

Yes, semaglutide is effective for weight loss in diabetics and non-diabetics. Your doctor will confirm if you meet the criteria required for semaglutide treatment.

Medically reviewed by:
Dr Crystal Wyllie Accreditations: MBBS, MRCGP (2015), DFSRH, DRCOG (2018)

Crystal qualified in Medicine at Barts and the London School of Medicine and Dentistry in 2010. She then trained as a GP in London hospitals and practices. She has a particular interest in reproductive, sexual and women’s health.

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Last reviewed: 10 Jan 2024

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