How does Wegovy work? A complete guide for UK patients

DoktorABC editorial team

Accurate, up-to-date health information written by our editorial team and reviewed by UK-registered prescribers.

What is Wegovy and what does it do?

Wegovy is the brand name for semaglutide 2.4 mg, a once-weekly injectable prescription medicine manufactured by Novo Nordisk. It is licensed by the MHRA for chronic weight management in adults with a BMI of 30 kg/m² or above, or 27 kg/m² or above with at least one weight-related health condition. A higher dose of 7.2 mg was approved by the MHRA on 6 January 2026 for patients who have reached and tolerated the standard maintenance dose.

Wegovy belongs to a class of medicines called GLP-1 receptor agonists. It works by mimicking a naturally occurring hormone in the gut to reduce appetite, slow digestion, and change the way the brain responds to food. The result, for most people, is a significant and sustained reduction in how much they eat, leading to meaningful weight loss over months of treatment.

How does Wegovy work?

Wegovy works by activating GLP-1 receptors throughout the body, producing effects on the pancreas, gut, and brain that together reduce hunger and food intake.

The GLP-1 mechanism

GLP-1 (glucagon-like peptide-1) is a hormone released naturally by cells in the small intestine after eating. It plays a central role in regulating blood sugar and appetite. Semaglutide, the active ingredient in Wegovy, is a synthetic analogue of GLP-1 that shares 94% sequence homology with the naturally occurring hormone (meaning its molecular structure is 94% identical to the hormone your body produces naturally). It binds to GLP-1 receptors throughout the body and activates them in the same way, but more potently and for much longer, due to chemical modifications that extend its half-life (the time it takes for the body to reduce the concentration of a drug in the bloodstream by half) to approximately seven days.

How it affects appetite

Once activated, GLP-1 receptors in the hypothalamus (the region of the brain that regulates hunger and satiety) reduce the drive to eat and quiet what many patients describe as constant background "food noise." The urge to snack, the preoccupation with the next meal, and the difficulty stopping eating when full all reduce significantly for most people on Wegovy.

How it affects digestion

Wegovy also slows gastric emptying, the rate at which food moves from the stomach into the small intestine. This means food stays in the stomach for longer after meals, producing a faster and more sustained feeling of fullness. Meals feel more satisfying at smaller portions, and the window between feeling hungry again extends.

How it affects blood sugar

By stimulating insulin secretion in response to rising blood glucose and suppressing glucagon (a hormone that raises blood sugar), Wegovy helps regulate blood sugar levels after meals. This effect is glucose-dependent, meaning it only activates when blood sugar is elevated, which significantly reduces the risk of hypoglycaemia (low blood sugar) in people without diabetes.

How does Wegovy work for weight loss specifically?

Wegovy reduces body weight primarily by reducing the amount of food people eat. The appetite suppression it produces is consistent and sustained, making it significantly easier to maintain a calorie deficit over time without the constant effort that dietary restriction alone requires.

The GIP component that Mounjaro adds is absent in Wegovy. Wegovy's weight loss mechanism works through GLP-1 alone, which still produces substantial results. The energy deficit created by reduced appetite leads the body to draw on stored fat for fuel, producing progressive fat loss over months of treatment.

In the STEP 1 trial (New England Journal of Medicine, 2021), participants on Wegovy 2.4 mg lost an average of 14.9% of their starting body weight over 68 weeks. The STEP UP trial, supporting the January 2026 MHRA approval of the 7.2 mg dose, showed average weight loss of 20.7% over 72 weeks.

How quickly does Wegovy work?

Wegovy begins acting from the first dose, but different effects appear at different speeds.

Within 24 to 48 hours

Many people notice subtle changes in appetite within the first day or two of their first injection. Meals may feel slightly easier to manage, or cravings feel less urgent. This reflects early GLP-1 signalling in the brain.

Weeks 1 to 4 (0.25 mg)

The 0.25 mg starting dose is sub-therapeutic and is designed to build tolerance rather than produce rapid results. Some patients experience little change on the scales at this stage. Appetite changes are often the first thing people notice, rather than visible weight loss.

Weeks 5 to 12 (0.5–1 mg)

Appetite suppression typically strengthens as the dose increases. Most people begin losing weight consistently during this phase. Energy levels often improve as weight starts to come down.

Months 3 to 6 (1.7–2.4 mg)

This is when results become most visible. Based on STEP 1 trial data, average weight loss reaches approximately 9% of starting body weight by month three and continues to build through to month six and beyond.

Months 6 to 18

Weight loss typically continues at a slower rate as the body approaches a new set point. In the STEP 1 trial, average weight loss reached approximately 14.9% by 68 weeks on the 2.4 mg dose. Long-term data confirms that results continue to accrue with consistent treatment.

Does Wegovy work for everyone?

Wegovy produces clinically significant weight loss in the large majority of people who take it at therapeutic doses. Over 80% of participants in the STEP 1 trial lost at least 5% of their starting body weight (the threshold considered clinically meaningful for metabolic health), and nearly 70% lost 10% or more.

That said, individual responses vary. The following factors influence how well Wegovy works for a given person.

Factors that affect results

• Dose: Results strengthen at higher doses. Patients who remain on lower titration doses due to side effects will typically see more modest outcomes.
• Dietary habits: Wegovy changes the biology of appetite; it does not replace the habits. Prioritising protein and reducing ultra-processed foods consistently improves outcomes.
• Activity levels: Regular physical activity improves results and helps preserve muscle mass during weight loss.
• Starting weight: People with higher starting weights tend to see larger absolute losses. Those with insulin resistance or type 2 diabetes may respond slightly differently.
• Consistency: Missing doses disrupts stable blood levels and appetite suppression. Injecting on the same day each week produces the most consistent results.
• Plateaus: Weight loss plateaus are normal, typically occurring around months five to eight, and do not mean Wegovy has stopped working.

Is Wegovy as good as Mounjaro?

At standard doses, Mounjaro produces greater average weight loss than Wegovy. The gap has narrowed significantly with the introduction of the 7.2 mg Wegovy dose.

In the SURMOUNT-5 head-to-head trial (New England Journal of Medicine, May 2025), Mounjaro 15 mg produced average weight loss of 20.2% versus 13.7% on Wegovy 2.4 mg over 72 weeks. At maximum doses, the two treatments are now broadly comparable in terms of efficacy.

For patients primarily focused on cost, Wegovy offers a meaningful advantage following Mounjaro's September 2025 price increase. For patients with type 2 diabetes, Mounjaro's dual mechanism offers additional benefits for blood sugar control. The right choice depends on your individual health profile, budget, and clinical assessment.

Why am I not losing weight on Wegovy?

If your weight loss has stalled or you are not seeing the results you expected, the most common reasons are as follows.

You are still in the titration phase

The 0.25 mg and 0.5 mg starter doses are designed to build tolerance, not produce rapid weight loss. Significant results typically begin at the 1 mg dose and above. Give treatment at least two to three months at a therapeutic dose before drawing conclusions.

Your diet has not changed significantly

Wegovy reduces appetite but does not eliminate it. If portion sizes, food choices, and eating patterns remain largely unchanged, the calorie deficit needed for weight loss may not be sufficient. Prioritising protein, reducing ultra-processed foods, and eating mindfully alongside treatment consistently improves outcomes.

You are missing doses or injecting inconsistently

Stable blood levels of semaglutide are what drive consistent appetite suppression. Missing doses or varying your injection day disrupts this. Set a weekly alarm and keep your injection day fixed.

You may need a dose increase

If you have been on the same dose for more than eight weeks without progress, speak to your prescriber about whether escalating to the next dose step is appropriate.

When should you escalate or review if Wegovy is not working?

Contact your prescriber if any of the following apply.

• You have completed four weeks at a dose with no change in weight or measurements and no side effects preventing escalation
• You have been on the maintenance dose for more than 12 weeks with no ongoing progress
• Side effects are preventing you from reaching a therapeutic dose
• Your weight loss has plateaued for more than four weeks with no change in measurements
• You are considering stopping treatment

NICE guidance recommends a formal clinical review at six months, with treatment typically continued only if at least 5% of starting body weight has been lost by that point. A further review at 12 months assesses whether ongoing treatment is appropriate.

How to use the Wegovy pen: Step-by-step guide

Wegovy is supplied as a pre-filled, single-use FlexTouch pen. Each pen contains four doses and lasts four weeks.

Before you inject

• Remove the pen from the fridge and allow it to reach room temperature for 15 to 30 minutes. Cold injections are more uncomfortable.
• Check the pen: confirm it is the correct dose, check the expiry date, and ensure the liquid is clear and colourless. Do not use it if it appears cloudy or contains particles.
• Wash your hands thoroughly with soap and water.
• Choose your injection site and clean it with an alcohol wipe. Allow it to dry fully before injecting.

Injecting

• Remove the pen cap.
• Press the pen firmly against the skin at a 90-degree angle on the chosen injection site.
• Press and hold the injection button until you hear a click, then continue holding for a further ten seconds to ensure the full dose is delivered.
• Remove the pen from the skin.

After injecting

• Dispose of the pen safely in a sharps bin. Do not recap or reuse the pen.
• Record the date of your injection.

How to take Wegovy: Injection day, rotation, and timing

Choosing your injection day

Inject Wegovy on the same day each week. You can change your injection day if needed, as long as it has been at least two days since your last dose. Consistency is important for maintaining stable blood levels.

Injection sites

The three approved injection sites are the abdomen (stomach area, avoiding the 5 cm zone around the navel), the outer thigh, and the upper arm. Rotate between sites each week to reduce the risk of skin irritation, lumps, or injection-site reactions.

Timing

Wegovy can be injected at any time of day, with or without food. Choose a time that fits your routine and stick to it.

Wegovy and alcohol: What you need to know

There is no direct chemical interaction between Wegovy and alcohol. However, combining the two can cause practical problems worth being aware of.

There is no requirement to stop drinking entirely on Wegovy. However, reducing intake, particularly during the titration phase when gastrointestinal side effects are most likely, will make treatment more comfortable and support better outcomes.

What to eat on Wegovy

Wegovy suppresses appetite but does not specify a particular diet. The following principles consistently produce better outcomes in patients on GLP-1 treatment.

Prioritise protein

Protein supports muscle preservation during weight loss and promotes satiety. Aim for adequate protein at each meal, using sources such as chicken, fish, eggs, legumes, Greek yoghurt, and lean meat.

Reduce ultra-processed foods

Ultra-processed foods (ready meals, crisps, biscuits, fast food) are calorie-dense, low in nutrients, and designed to override satiety signals. Reducing them significantly improves the calorie deficit that Wegovy's appetite suppression creates.

Eat smaller, regular meals

Because Wegovy slows gastric emptying, large meals can cause discomfort, nausea, and bloating. Smaller, more frequent meals are typically better tolerated, particularly in the early weeks of treatment.

Stay hydrated

Adequate hydration reduces headaches, supports kidney function, and helps manage constipation, one of the more common side effects of treatment. Aim for at least 1.5 to 2 litres of water daily.

Avoid lying down after eating

Wegovy's effect on gastric emptying can increase the likelihood of acid reflux after meals, particularly large ones. Staying upright for at least 30 minutes after eating helps.

Does Wegovy need to be refrigerated?

Yes. Wegovy pens must be stored in the refrigerator between 2°C and 8°C until first use. They must not be frozen.

How long can Wegovy be out of the fridge?

Once removed from the refrigerator, a Wegovy pen can be stored at room temperature (up to 30°C) for up to 28 days, provided it is kept in its original carton and away from direct light and heat. After 28 days at room temperature, the pen should be disposed of even if doses remain.

How long does Wegovy last in the fridge?

An unopened Wegovy pen stored correctly in the refrigerator can be kept until the expiry date printed on the packaging. Once the pen has been used for the first injection, it can be stored either in the fridge or at room temperature (up to 30°C) for up to 28 days.

Always check the expiry date before injecting and discard any pen that has been stored outside these conditions.

Is there a Wegovy tablet?

Not yet in the UK. As of April 2026, the Wegovy pill has not been approved for use in the United Kingdom.

An oral semaglutide tablet (25 mg, once daily) was approved by the US Food and Drug Administration in December 2025 and launched in the United States in January 2026. It is developed by Novo Nordisk and works through the same mechanism as the injection, using a technology that enables semaglutide to be absorbed through the gut wall when taken under specific conditions (on an empty stomach with a small amount of water, at least 30 minutes before food or drink).

The OASIS-4 clinical trial showed average weight loss of approximately 16.6% over 64 weeks with the 25 mg daily pill, broadly comparable to the standard 2.4 mg weekly injection.

Novo Nordisk submitted the oral formulation to the MHRA and EMA for regulatory review in the second half of 2025. A decision from the MHRA is expected in late 2026. NHS availability, if approved, would require a subsequent NICE health technology appraisal and is unlikely before 2027 at the earliest.

For now, the Wegovy injection remains the only MHRA-licensed semaglutide option for weight management in the UK. If you are interested in the oral option, speak to your prescriber about the current status when the time comes.

Final thoughts

Wegovy is a well-evidenced, MHRA-licensed treatment that works by harnessing the body's own appetite-regulating biology. For most people who take it consistently at a therapeutic dose, alongside meaningful dietary changes and activity, it produces significant and sustained weight loss. Understanding how it works, what to expect at each stage, and how to use it correctly makes the treatment process more manageable and the results more predictable.

If you have questions about whether Wegovy is appropriate for you, or concerns about how your treatment is progressing, the right first step is always a conversation with your GP or a UK-registered prescriber.

FAQ

The DoktorABC medical advisory board

Dr. Roland Ruiken

Medical advisor, Norway

Dr. Viktor Simunovic

Medical advisor, Croatia

To the medical advisory board