Home | Blog | Weight loss | Everything on weight loss injections

What are weight loss injections?

Weight loss injections are a type of prescription medication for weight loss that can be more effective than weight loss pills or low-calorie diets. They’re licensed for people with a BMI of 30 or more (or slightly less if you also have certain health conditions), although the NHS will usually only fund injection weight loss treatment if your BMI is 35 or more.

Medically reviewed by

Daniel Atkinson, GP Clinical Lead

Go to

Reviewed on Jul 11, 2024. by Dr Daniel Atkinson GP Clinical Lead Registered with GMC (No. 4624794) Next review due on Jul 11, 2027.

Last updated on Jul 09, 2024.

Was this article useful?

Is weight loss treatment right for you?

Enter your height and weight below to check your BMI, and find out if weight loss treatment could help you.

Height

ft/in

Feet

Inches

Weight

lbs

Stone

Pounds

The weight loss injections available are Liraglutide (under various brand names), Wegovy (semaglutide), and Mounjaro (tirzepatide). Talk to us if you’re thinking of trying weight loss injections and one of our clinicians will explain how each of them works and answer any questions that you might have.

How do weight loss injections work?

Although the active ingredients in weight loss injections (WLIs) have different names, they’re mostly from the same family of drugs and work in a similar way.

Semaglutide (Wegovy) and Liraglutide (Saxenda, Nevolat, Biolide, and Plaobes) both work similarly, in that they replicate the hormone GLP-1, which is normally released after you eat a large meal. This hormone:

Tells your brain you’re full, which decreases your appetite.
Slows digestion, meaning you feel fuller for longer.
Tells your pancreas to produce more insulin, lowering your blood sugar levels.

By mimicking this hormone, GLP-1 medications help you eat fewer and smaller portions, which helps you lose weight.

Mounjaro (tirzepatide) is slightly different, in that it’s both a GLP-1 receptor and a GIP receptor agonist. It works in a similar way to Wegovy, by suppressing your appetite and signals your brain to make you feel full and satiated (thus preventing overeating). However Mounjaro appears to reduce more of the visceral fat around abdominal organs than some of the other weight loss injections, while preserving more of your muscle mass.

Do they actually help you lose weight?

Yes, these injection drugs can cause significant and sustained weight loss when used correctly. Usually combined with a reduced calorie diet and an increase in physical activity.

There’s clinical evidence that liraglutide, the active ingredient in Saxenda and others, helps you lose significant weight sustainably, with the added, unique benefit of improving your glycaemic levels.

Wegovy clinical trials found statistically significant weight loss results for participants when compared with a placebo group. The weight loss results were observed in participants irrespective of their age, gender, race, ethnicity and initial BMI.

Likewise, in a clinical study, people using Zepbound lost up to 20% of body weight over 72 weeks.

But it’s important to continue to practise the healthier habits mentioned above – eating healthily and exercising regularly – after finishing treatment to make sure that you don’t regain the weight you’ve lost during treatment.

Are Wegovy and Ozempic better than Saxenda?

Both semaglutide (found in Ozempic and Wegovy) and liraglutide (Saxenda and its generics) mimic the hormone GLP-1. These active ingredients are very similar to the naturally occurring GLP-1 hormone.

Saxenda has been approved as a weight loss medication, and Ozempic is a type-2 diabetes medication. But clinicians saw significant weight loss in diabetes patients using this medication. Initially, some clinicians prescribed Ozempic as an off-label weight loss injection. But since then, semaglutide has been licensed for use in weight loss under a new brand name: Wegovy.

A study that compared the effectiveness of semaglutide, with liraglutide and placebo, found that injecting semaglutide can result in significant weight loss with minimal side effects, and about 37-65% of people who take it will see a decrease of 10% of their excess weight in up to 52 weeks after the treatment starts. In the same time frame, only 25.2% of people taking the highest dose of liraglutide (3mg) achieved the same 10% loss of excess body weight.

It’s important to take into account that the study on the efficacy of semaglutide was done on people without type 2 diabetes, whilst everyone on the study on the efficacy of liraglutide was diagnosed with type 2 diabetes before the study.

What’s the difference between Saxenda and Wegovy?

Saxenda (liraglutide) and Wegovy (semaglutide) are similar weight loss medications. Both treatments belong to the same category of medication (GLP-1 receptor agonists).

However, liraglutide medications need to be used every day, whereas semaglutide (Wegovy) only needs to be used once a week, making it a more convenient option. Wegovy has also been shown to be more effective than liraglutide medications in clinical trials.

How is Mounjaro different from other weight loss treatments?

Mounjaro contains the active ingredient tirzepatide, which differs from the active ingredients in Wegovy (semaglutide) and Saxenda (liraglutide). While tirzepatide, semaglutide, and liraglutide all act as GLP-1 receptor agonists, tirzepatide also acts as a GIP receptor agonist. Although GIP receptors work similarly to GLP-1 receptors, this dual action makes tirzepatide more effective for weight loss. This is proven in studies that show individuals using tirzepatide had greater weight loss than those using semaglutide.

Are weight loss injections safe?

Yes, when used correctly weight loss injections are safe. However, all weight loss treatments can cause side effects.

Ozempic is prescribed for diabetes. It is safe to use for weight loss but is an off-label treatment when prescribed for this purpose.

Wegovy is a prescription treatment specifically for weight loss and has undergone rigorous clinical trials. But it’s common for people who use it to experience nausea, particularly when starting the medication or increasing the dose. Similar to Wegovy, the most common side effect reported for Mounjaro is nausea. There are ways you can limit the effects of nausea when using the injections, by drinking plenty of water and avoiding more stodgy, fattier foods.

The side effects of stopping weight loss injections tend to be minimal. Since they’re not addictive medications, it’s not likely they’ll cause withdrawal.

Some people may find that they put weight on again after finishing treatment, because they’re no longer feeling the appetite-suppressing properties of the drug. For this reason, it’s important to adopt and adhere to healthy eating and regular exercise while you’re taking treatment, and continue these habits after completing treatment. This will help you to maintain the weight loss you’ve achieved and lower your risk of regaining weight.

This page was medically reviewed by Dr Daniel Atkinson, GP Clinical Lead on Jul 11, 2024. Next review due on Jul 11, 2027.

Last updated on Jul 09, 2024.

How we source info.

When we present you with stats, data, opinion or a consensus, we’ll tell you where this came from. And we’ll only present data as clinically reliable if it’s come from a reputable source, such as a state or government-funded health body, a peer-reviewed medical journal, or a recognised analytics or data body. Read more in our editorial policy.

Tell us what you want to hear.

Have a subject you’d like us to cover in a future article? Let us know.

Give us the inbox treatment.

We're making healthcare more about you. Sign up to our newsletter for personalised health articles that make a difference.

Disclaimer: The information provided on this page is not a substitute for professional medical advice, diagnosis, or treatment. If you have any questions or concerns about your health, please talk to a doctor.