What are weight loss injections? A guide to obesity treatment drugs

Understanding weight loss medications

In this guide

A guide to obesity treatment drugs

Obesity treatment drugs are medications that can help people with obesity lose weight.

There are many different types of obesity treatment drugs with different effects and routes of administration (ways of taking them). Some are not approved for use in the UK. Others are available on prescription from the NHS or a private healthcare provider. One is available over the counter from pharmacies.

SemaPen is a private healthcare provider that offers two treatment programmes. These programmes use injectable weight loss medications called 'Wegovy' and 'Mounjaro'.

Who are obesity treatment drugs for?

Obesity treatment drugs are for people

with obesity,
who have tried diet and exercise but still struggle to lose weight.

It's important to understand that these drugs don't work as 'quick fixes' and they're not a replacement for traditional weight loss methods. They're meant to support a sensible diet and regular exercise by helping patients lose weight more quickly and effectively.

Am I eligible for prescription medication?

Remember that not all drugs work for all people. That's why it's important to get medical advice before you start a course of treatment – especially when that treatment involves prescription drugs.

To get a prescription, you must have a consultation with a healthcare professional. They'll ask you questions to figure out whether the drug is a good fit for you.

In the case of obesity treatment drugs, they'll ask you about things like your weight, your ethnic background and whether you have certain conditions. That's because all these things can affect how the drug works and whether it's safe for you to take.

At a bare minimum, however, you must meet one of these criteria:

You have obesity (your BMI is greater than 30).
You have a BMI greater than 27 and have another serious medical condition that's linked to obesity.

You must also have tried diet and exercise without success.

What are weight loss injections?

Weight loss injections are a type of medication used to treat obesity. Examples include Wegovy, Mounjaro and Saxenda.

These three medications each work slightly differently. However, they have a few things in common:

They're administered (taken) with an injection pen.
They help people lose weight by mimicking natural 'hunger hormones' called incretins.

You might have also heard of Ozempic. This is an injectable drug with the same active ingredient as Wegovy. However, Ozempic is used to treat type-2 diabetes, while Wegovy is prescribed for obesity.

How do I take injectable obesity treatment drugs?

Most injectable obesity treatments are self-administered. This means you can inject yourself with the medication at home.

It's normal to feel nervous when you first do this. However, it's quite easy to do and most people experience very little pain. The needle is tiny and is enclosed in a pen-shaped cartridge to make it easy to use.

You'll get full instructions when you begin your treatment. But generally speaking, it's as simple as placing the pen against your skin and applying a little pressure. It's best to inject it into your tummy or thigh.

How often should I take the injections?

This varies depending on the medication you're prescribed.

SemaPen's treatment programmes use Wegovy and Mounjaro. You only need to take these once per week for the treatment to work. The dose increases every four weeks until you reach the maintenance (maximum) dose.

Other medications have different dosing schedules. Saxenda, for instance, must be taken daily.

What results can I expect?

Results are different for everyone. They vary depending on the medication you take, as well as your lifestyle and the way your body works.

Patients who take Wegovy will typically lose 15% of their body weight. This means if you weigh 17 stone when you start taking the medication, you'd weigh about 14 stone and seven pounds with sustained treatment.

For Mounjaro, the typical weight loss is 21%. So, if you were 17 stone before treatment, you'd weigh around 13 stone and six pounds after treatment.

Bear in mind that these are averages, though. Your actual weight loss may be higher or lower.

What are the possible side effects?

All drugs can cause side effects. A side effect is any kind of unwanted result from taking a drug.

Side effects are quite common with Mounjaro and Wegovy. However, they tend to be quite mild and often go away or get better as you continue treatment.

The most common side effects are nausea and stomach upsets, including diarrhoea, vomiting and pain in the belly. In clinical trials, these side effects were less common with Mounjaro than Wegovy.

Serious side effects can happen but are rare. You can read more about them in our detailed guide to the side effects of weight loss medications.