Wegovy ingredients and what they do

Ready to take the next step? See if you're eligible for expert-led weight loss support.

Curious about the ingredients in Wegovy? Discover what's in the injection and the roles that different ingredients play.

Thinking about using Wegovy for weight loss? It's only natural to wonder what is inside the injection you will be taking every week.

You'll receive a patient information leaflet with a full list of the ingredients, but it won't provide much detail about what the ingredients actually do.

That's why we've created this guide. Read on to learn how Wegovy's active ingredient supports weight loss and what the inactive ingredients are used for.

Wegovy ingredients list

Wegovy comes as a pre-filled injection pen designed for you to inject yourself easily at home.

Each pen comes loaded with four weeks' worth of medication. This solution is made up of the following ingredients:

Semaglutide
Disodium phosphate dihydrate
Sodium chloride
Hydrochloric acid/sodium hydroxide
Water

Here's what each ingredient is used for, starting with the active ingredient – semaglutide.

Semaglutide: the active ingredient in Wegovy

The star of the show is semaglutide, a medicine that belongs to a group of drugs known as 'GLP-1 receptor agonists'.

GLP-1 is a hormone our bodies naturally produce after eating. It helps regulate appetite and slows the rate at which the stomach empties. It also supports healthy blood sugar control.

Semaglutide mimics this hormone. It acts on the same receptors to help you feel full sooner and stay satisfied for longer. In a large clinical trial, people who combined semaglutide with healthy lifestyle changes lost around 15% of their body weight on average.

Semaglutide is also the active ingredient in Ozempic, a drug licensed for type 2 diabetes. However, Wegovy contains a higher dose specifically studied and approved for weight management in people who are living with overweight or obesity.

The other Wegovy ingredients and what they do

Alongside semaglutide, Wegovy contains a short list of inactive ingredients. These ingredients do not cause weight loss but play important roles in keeping medicines stable, sterile and comfortable to inject.

According to the European Medicines Agency, you'll find the following inactive ingredients in Wegovy.

Disodium phosphate dihydrate

This buffering agent is used to keep injectable medicines at a steady, skin-friendly pH. That's so they stay stable from factory to fridge to injection.

By preventing the liquid from becoming too acidic or alkaline, it protects the medicine and helps make the injection more comfortable. Its role is purely to maintain the balance and quality of the medication.

Sodium chloride

This familiar compound – ordinary salt – is used to keep injectable solutions close to the body's natural salt balance. That means the injection feels gentle rather than sharp or stinging.

Salt also helps the liquid stay stable while stored and makes sure the active ingredient remains evenly mixed.

Hydrochloric acid and sodium hydroxide

These two ingredients work together as pH adjusters. If a solution is too acidic, a trace of sodium hydroxide balances it. If it's too alkaline, a little hydrochloric acid brings it back.

During preparation, the two ingredients neutralise one another, leaving only water and harmless salts.

Water

Many injectable solutions contain sterile, purified water. It carries active and inactive ingredients evenly so the dose flows smoothly under the skin.

Anything else?

No – that's the complete list. Wegovy contains no preservatives, colourings or animal-derived ingredients.

Are any of the ingredients in Wegovy unsafe?

For most people, no.

The active ingredient, semaglutide, has been tested in large international trials and is closely monitored by healthcare professionals for its safety and effectiveness.

The other ingredients feature widely in other injectable medicines and are used in very small, approved amounts. Nothing here is unusual or unique to Wegovy.

That said, Wegovy isn't suitable for everyone. There are some scenarios where taking Wegovy could harm you or others. That includes:

If you're allergic to any of the ingredients in the medication
If you use other weight loss medicines or another GLP-1 treatment
If you are taking any medicines that affect semaglutide
If you have type 1 diabetes, severe kidney or liver problems, severe heart failure or serious stomach or bowel issues such as gastroparesis
If you're pregnant, breastfeeding or planning to get pregnant within 2 months (we don't know if Wegovy harms unborn babies or passes into breast milk)

When you take your SemaPen consultation, we'll ask about your allergies, lifestyle and medical history to make sure it's safe for you to start treatment.

Ingredients in Ozempic vs Wegovy ingredients

Because both medicines contain semaglutide, you might wonder if Wegovy and Ozempic are identical.

The two medications share the same active ingredient and have a similar list of inactive ingredients. The key differences are dosage and intended use. Ozempic is approved for blood-sugar control in people with type 2 diabetes, while Wegovy is licensed for weight management at a higher dose.

How SemaPen supports your weight loss

Starting treatment with a weight loss injection is about more than understanding ingredients. You deserve a safe, expert-led plan that protects your health and helps you achieve the results you want. That's why we offer lots of extra support with our weight loss Programmes.

You can expect:

A clinician-led assessment: our specialists review your health and check for allergies or contraindications. This is to make sure Wegovy is safe for you before giving you the go-ahead.
An expert weight loss plan: SemaPen's Programmes are designed by UK obesity experts to help keep you on track from start to finish.
Ongoing monitoring and support: we check in regularly to track your weight, side effects and overall wellbeing. And you can always contact our experts for advice.
Evidence-based care: our Programmes are built on data from leading studies, including the STEP semaglutide trials, to keep your treatment aligned with the latest science.

With our support, you can focus on building healthy and sustainable habits while we handle your clinical care.

Thinking about Wegovy?

The most important thing for us is that you feel safe and confident while enrolled on our Wegovy or Mounjaro weight loss programmes.

If you have any questions, please don't hesitate to get in touch with our friendly experts. We're always ready to help.

Ready to take the next steps on your weight loss journey? It's easy to get started. All you have to do is take our digital consultation. We'll recommend the right treatment option for you straight away.

Sources

1. Wilding, J.P.H. et al. (2021) "Once-weekly semaglutide in adults with overweight or obesity" The New England Journal of Medicine, 384(11) https://doi.org/10.1056/NEJMoa2032183

2. European Medicines Agency (2025) European Public Assessment Report (EPAR) for Wegovy. Retrieved from https://www.ema.europa.eu/en/documents/product-information/wegovy-epar-product-information_en.pdf

This article was reviewed and approved by Alice Fletcher, Lead Bariatric Dietitian, on 29 September 2025.

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