By Anna Fenech, Pharmacist Independent Prescriber
If you have been researching Wegovy for weight loss, you may be wondering what the medication actually does in your body and how it can help you lose weight. Wegovy contains semaglutide, a medicine that mimics a naturally occurring hormone called GLP-1. It works mainly by reducing appetite, increasing feelings of fullness and helping regulate blood glucose levels.
As a Pharmacist Independent Prescriber, I regularly assess whether prescription weight loss treatment is appropriate for an individual. In this guide, I will explain how Wegovy works, what you can realistically expect during treatment, who may be suitable for it, and the side effects and safety considerations you should understand before starting.
What is Wegovy?
Wegovy is a prescription medicine containing semaglutide. It belongs to a group of medicines known as GLP-1 receptor agonists.
GLP-1 stands for glucagon-like peptide-1. It is a hormone naturally released by the gut after eating. One of its roles is to communicate with areas of the brain involved in appetite and food intake.
Wegovy acts in a similar way to this natural hormone. It is used alongside a reduced-calorie diet and increased physical activity for weight management in people who meet the relevant clinical criteria.
How does Wegovy work for weight loss?
Wegovy does not work by simply “burning fat”. Its main effect is to change the signals that regulate hunger, fullness and food intake.
1. Wegovy reduces appetite
Semaglutide activates GLP-1 receptors in parts of the brain involved in appetite regulation. This can make you feel less hungry and fuller for longer, while also reducing food cravings.
For many patients, this is one of the most noticeable changes. Rather than having to rely on willpower to ignore persistent hunger, you may find that smaller portions feel satisfying and that you think about food less frequently.
This can make it easier to maintain a calorie deficit, which is necessary for weight loss.
2. It helps you feel fuller after eating
Semaglutide also slows gastric emptying, meaning food can pass through the stomach more slowly. This contributes to the feeling of fullness after a meal.
This is one reason why portion sizes may naturally become smaller while taking Wegovy. It is also why eating very large or high-fat meals can sometimes make gastrointestinal side effects such as nausea or indigestion more noticeable.
3. Wegovy affects blood sugar regulation
GLP-1 has an important role in glucose regulation. Semaglutide helps the body release insulin when blood glucose levels are elevated and reduces the release of glucagon, a hormone that raises blood glucose.
The result is better regulation of blood sugar, particularly after eating. The effect is glucose-dependent, so the risk of low blood sugar is generally low when Wegovy is used on its own in people without diabetes. The risk can be higher when semaglutide is used alongside medicines such as insulin or sulfonylureas.
How quickly does Wegovy work?
Wegovy treatment is normally started at a low dose and increased gradually. This is important because it gives your body time to adjust and can help reduce gastrointestinal side effects.
For the standard Wegovy injection regimen, the dose is increased at four-week intervals from 0.25 mg to 0.5 mg, 1 mg, 1.7 mg and then a maintenance dose of 2.4 mg, provided the treatment remains suitable and tolerated.
You should therefore not expect the full effect immediately.
Some people notice reduced hunger within the first few weeks, while for others the effect becomes more apparent as the dose increases. Weight loss tends to occur progressively rather than all at once.
How much weight can you lose with Wegovy?
Individual results vary considerably, so I would always caution against using somebody else’s weight loss as a personal target.
However, clinical trial evidence gives us a useful indication of what can be achieved. In the large STEP 1 study, adults with overweight or obesity receiving semaglutide 2.4 mg alongside lifestyle intervention lost an average of 14.9% of their starting body weight after 68 weeks, compared with 2.4% with placebo and lifestyle intervention.
In the same study, 86.4% of participants receiving semaglutide lost at least 5% of their initial body weight, 69.1% lost at least 10%, and 50.5% lost at least 15% by week 68.
These are averages from a clinical trial, not a guarantee of what an individual patient will achieve. Your response can be affected by factors including your starting weight, medical history, other medicines, dose tolerance, eating habits and activity levels.
What should you expect during Wegovy treatment?
A gradual approach is important.
During the first few weeks, the focus is usually on tolerating the medicine and establishing the correct dose, rather than trying to lose as much weight as possible as quickly as possible.
As treatment progresses, you may notice:
- Reduced hunger between meals
- Feeling satisfied with smaller portions
- Fewer food cravings
- More control over snacking
- Gradual changes in body weight
- Improvements in some weight-related health measures
Your weight may not decrease at exactly the same rate every week. Periods where your weight stays relatively stable can occur, and this does not necessarily mean that treatment has stopped working.
As a prescriber, I look at the overall pattern of response rather than focusing on individual weigh-ins.
Who is Wegovy suitable for?
Wegovy is not appropriate for everyone who wants to lose weight. In the UK, it is licensed for weight management alongside diet and physical activity in adults with:
- A BMI of 30 kg/m² or above, or
- A BMI of 27 kg/m² to below 30 kg/m² where there are weight-related health problems.
A proper clinical assessment is important because BMI is only one part of the prescribing decision. Your medical history, current medicines, previous treatments and any relevant health conditions also need to be considered.
If you are considering prescription treatment, you can find out more about our Wegovy weight loss treatment and the clinical assessment process.
Who may not be suitable for Wegovy?
A clinical consultation is particularly important if you have certain medical conditions or take medicines that could affect the safety of treatment.
For example, semaglutide requires particular consideration in people with a history of pancreatitis, significant gastrointestinal problems such as severe gastroparesis, or conditions where dehydration could present a greater risk.
Wegovy should not be used during pregnancy or breastfeeding. If you are planning a pregnancy, semaglutide should be stopped at least two months beforehand because it remains in the body for a prolonged period.
It is also important to tell your prescriber about all medicines you take, particularly diabetes treatments. Wegovy should not be combined with another GLP-1 receptor agonist.
What are the side effects of Wegovy?
The most common side effects are gastrointestinal. These include:
- Nausea
- Diarrhoea
- Vomiting
- Constipation
- Abdominal discomfort or pain
- Indigestion
These effects are often most noticeable while the dose is being increased and are generally mild to moderate and temporary. In the STEP clinical trials, nausea, diarrhoea and vomiting were among the most frequently reported adverse effects.
This is one reason I would not recommend increasing the dose more quickly than prescribed. If gastrointestinal symptoms are significant, your clinician may consider delaying the next dose increase or temporarily using the previous dose.
When should you seek medical advice?
Most side effects can be managed with appropriate advice, but some symptoms require prompt medical attention.
Persistent, severe abdominal pain, particularly if it radiates to the back, can be a symptom of acute pancreatitis and should be assessed urgently. Severe vomiting or diarrhoea can also cause dehydration, which is particularly important if you have kidney problems.
If you experience a sudden loss of vision, including partial loss of vision, you should seek urgent medical assessment. This is a rare but important potential adverse effect identified in the current product information.
You should always discuss unexpected or persistent symptoms with your prescriber rather than simply stopping or changing the dose yourself.
Is Wegovy a long-term weight loss treatment?
For many people, weight management needs to be approached as a long-term health issue rather than a short-term diet.
Wegovy can help reduce appetite and support sustained weight loss while you are taking it, but it does not remove the underlying tendency to regain weight. Lifestyle habits remain an important part of treatment.
It is also worth understanding that weight regain can occur after stopping semaglutide. For this reason, decisions about continuing, adjusting or stopping treatment should be made with your prescriber and should take into account your response, side effects and longer-term health goals.
Wegovy: the key points
Wegovy works by mimicking GLP-1, a hormone involved in appetite and glucose regulation. By activating GLP-1 receptors, semaglutide can reduce hunger, increase feelings of fullness, slow gastric emptying and support better blood glucose regulation.
For suitable patients, clinical trials have demonstrated substantial average weight loss over a period of around a year or longer, but individual results vary.
The most common side effects are gastrointestinal, particularly nausea, diarrhoea, vomiting and constipation. Starting at a low dose and increasing gradually is an important part of using the medicine safely.
Most importantly, Wegovy is a prescription medicine, not a general-purpose slimming product. Whether it is appropriate for you should be established through an individual clinical assessment.
Anna Fenech, Pharmacist Independent Prescriber
At Direct Weight Loss, our approach is to assess each patient’s circumstances carefully before prescribing, with appropriate follow-up and support throughout treatment.