Over the past couple of years, interest in weight loss treatments has soared. Drugs like Wegovy, Mounjaro and Saxenda are creating a buzz for their revolutionary approach to weight management. So if you’re curious about them, you’re certainly not alone.
These medicines promise to curb your appetite and keep you fuller for longer. That makes it easier to stick to a healthy, balanced diet, which often leads to significant weight loss. Wegovy, one of the most popular options, has been available in the UK since September 2023. Here’s exactly how it works.
What is Wegovy?
Wegovy is a prescription medication for weight loss, which contains the same active ingredient (called semaglutide) as Ozempic. (Despite some misleading headlines, Ozempic is only prescribed for type 2 diabetes, not for losing weight.) It’s a once-a-week injection that you administer using a simple pre-filled pen—into your upper arm, thigh, or stomach. Here’s some detailed advice on how to inject Wegovy.
The treatment has shown impressive results in clinical trials. In the STEP 1 clinical trial, nearly 2,000 eligible adults took Wegovy once a week over the course of 16 months. On average, they lost 15% of their body weight, while almost a third lost 20% of their body weight or more. By contrast, participants who relied on lifestyle changes alone lost just 2.4% of their starting weight.
Wegovy’s active ingredient: Semaglutide
The active ingredient in Wegovy is semaglutide.
Semaglutide belongs to a class of drugs called GLP-1 receptor agonists. Along with tirzepatide and liraglutide (the active ingredients in Mounjaro and Saxenda respectively), it mimics a hormone called glucagon-like peptide 1 (GLP-1), which helps the body suppress appetite, aka it helps you feel fuller for longer.
Because semaglutide also improves blood sugar control, it was originally intended to treat type 2 diabetes, but it soon became apparent that semaglutide can also help people lose weight.
How does Wegovy work?
Semaglutide is a GLP-1 receptor agonist, meaning it acts like a natural hormone called GLP-1.
It fits into GLP-1 receptors in your digestive system, pancreas, and brain—like a key fitting into a lock. Once these receptors are activated, they trigger processes in your body that can support weight loss.
Suppresses appetite
First, semaglutide interacts with GLP-1 receptors in a part of the brain called the hypothalamus, which plays a big part in regulating hunger. The upshot is you lose your appetite. Hunger signals are dampened down, and feelings of fullness are increased.
Slows digestion
Semaglutide slows down the rate of gastric emptying (stomach emptying), which means glucose and other macronutrients are released into your bloodstream more gradually. It also helps you feel fuller for longer.
Regulates blood sugar
Semaglutide binds to GLP-1 receptors in the pancreas, which prompts the pancreas to release insulin after meals. Insulin shunts glucose out of the bloodstream and into the cells, where it’s needed for energy.
Semaglutide also blocks the release of another hormone called glucagon, which performs the opposite function to insulin (i.e., it stops the blood sugar from dipping too low). As a result, people who have taken semaglutide can avoid undesirable blood sugar spikes after meals. That means no sugar crashes either—your blood sugar stays balanced throughout the day.
How long does Wegovy take to work?
Wegovy starts working from the first dose, and many people notice reduced hunger within days. Significant weight loss takes time, though—think of it as a marathon, not a sprint.
So how long will it take the scale to budge? Well, in the STEP 1 trial, participants had lost just over 2% of their body weight on average at their four-week weigh-in. That’s around 2kg for a person weighing 100kg, or around half a kilo a week. (Not a dramatic result, but certainly nothing to be sniffed at.)
Check out our Wegovy week-by-week guide for more info.
Of course, the exact outcome will depend on the person. Everybody is different, and it may also depend on other factors like the quality of your diet, your stress levels, and how much you exercise. Remember—Wegovy should be taken as part of a holistic approach to weight loss involving positive lifestyle changes.
How long do you take Wegovy for weight loss?
Wegovy is designed for long-term use. You’ll start on the lowest possible dose of 0.25mg, to help minimise side effects. At the start of month two, you’ll increase the dose to 0.5mg, before reaching the ‘treatment’ dose of 1mg at month 3. After that, some people will stay at 1mg, while others will increase to a ‘maintenance dose’ of 1.7mg or 2.4mg. It’s all down to how well your body tolerates the medication. (Read more about the Wegovy dosing schedule.)
You’ll usually discontinue the treatment once your goal weight loss has been achieved. Patients who receive Wegovy on the NHS can only be prescribed the drug for two years. So always talk to your doctor about how to stop Wegovy safely, while minimising the risk of weight gain.
Side effects of Wegovy
Wegovy is a prescription medicine that isn’t available over the counter—you can only access the drug if your clinician says it’s right for you. And like most medicines, it comes with possible side effects. Here are some common wegovy side effects to look out for:
- Digestive problems (nausea, diarrhoea, vomiting, constipation, burping, bloating or an upset stomach)
- Stomach pain
- Tiredness
- Headache
- Dizziness
- Heartburn
- Low blood sugar (more likely for people with diabetes on other anti-diabetic medications)
- Change in the way food and drink tastes.
These side effects are typically mild and will clear up by themselves. But always ask your clinician if you’re concerned.
Alternatives to Wegovy
Wegovy isn’t the only medication that can help you on your weight loss journey. There are alternatives such as:
- Mounjaro: A weekly injection containing the molecule tirzapatide. Like Wegovy, it is a GLP-1 receptor agonist, but also mimics another naturally occurring hormone called GIP.
- Saxenda: This is a once-daily injection containing the molecule liraglutide. It is a GLP-1 receptor agonist, and was the first weight loss injection to be approved for use in the UK.
These medications aren’t magic solutions, but they can be transformative for people who’ve struggled with traditional weight loss methods.
If you’re interested in exploring weight loss medication, a clinician at Voy can let you know whether it's suitable for you—and which options might be best. Just fill in this short form and we’ll get right back to you.
FAQs
Can I take Wegovy with other medications?
It depends on the medication! Some drugs, like insulin, interact with Wegovy in undesirable ways, so always tell your doctor if you’re taking any other drugs. That applies to over the counter and prescription medications, as well as vitamins and herbal supplements.
Who should avoid using Wegovy?
You should avoid using Wegovy if you’re pregnant or breastfeeding, if you have ever had an allergic reaction to any of the ingredients, if you have a family or personal history of thyroid cancer, or if you are under the age of 12. And it goes without saying, don’t take Wegovy if you don’t meet the eligibility criteria.
¹“Accessing Wegovy for Weight Loss: Everything You Need to Know.” Department of Health and Social Care, 4 Sept. 2023, healthmedia.blog.gov.uk/2023/09/04/accessing-wegovy-for-weight-loss-everything-you-need-to-know.
²Kommu, Sharath, and Philip Whitfield. "Semaglutide." StatPearls - NCBI Bookshelf,
11 Feb. 2024, www.ncbi.nlm.nih.gov/books/NBK603723.
³"Liraglutide for Managing Overweight and Obesity.” National Institute of Health and Care Excellence. 9 Dec. 2020, www.nice.org.uk/guidance/ta664/chapter/1-Recommendations.
⁴Ryan, Donna H., et al. "Long-term Weight Loss Effects of Semaglutide in Obesity Without Diabetes in the SELECT Trial." Nature Medicine, vol. 30, no. 7, May 2024, pp. 2049–57. https://doi.org/10.1038/s41591-024-02996-7.
⁵"Semaglutide for Managing Overweight and Obesity.” National Institute of Health and Care Excellence. 8 Mar. 2023, www.nice.org.uk/guidance/ta875/chapter/1-Recommendations.
⁶"Tirzepatide for Managing Overweight and Obesity." National Institute of Health and Care Excellence. 23 Dec. 2024, www.nice.org.uk/guidance/ta1026/chapter/1-Recommendations.
⁷“Wegovy: Summary of Product Characteristics.” European Medicines Agency. www.ema.europa.eu/en/documents/product-information/wegovy-epar-product-information_en.pdf. Accessed 20 Jan. 2025.
⁸“Wegovy Dosing Schedule.” Wegovy. www.wegovy.com/taking-wegovy/dosing-schedule.html. Accessed 20 Jan. 2025.
⁹“Wegovy Side Effects.” Wegovy. www.wegovy.com/taking-wegovy/side-effects.html. Accessed 20 Jan. 2025.
¹⁰Wilding, John P. H., et al. "Once-Weekly Semaglutide in Adults With Overweight or Obesity." New England Journal of Medicine, vol. 384, no. 11, Feb. 2021, pp. 989–1002. https://doi.org/10.1056/nejmoa2032183.
¹¹Wilding, John P. H., et al. "Weight Regain and Cardiometabolic Effects After Withdrawal of Semaglutide: The STEP 1 Trial Extension." Diabetes Obesity and Metabolism, vol. 24, no. 8, Apr. 2022, pp. 1553–64. https://doi.org/10.1111/dom.14725.
¹²Zheng, Zhikai, et al. "Glucagon-like Peptide-1 Receptor: Mechanisms and Advances in Therapy." Signal Transduction and Targeted Therapy, vol. 9, no. 1, Sept. 2024, https://doi.org/10.1038/s41392-024-01931-z.
