Weight Loss Injections

What are the different weight loss injections?

There are several different weight loss injections, and some are already licensed in the UK, and some are still waiting for approval. Saxenda is a licensed treatment and Wegovy has recently been licensed.

Other injections can be prescribed as an ‘off-label’ treatment. Off-label prescribing allows a GP to prescribe medication if they think a patient could benefit, even if this is not the primary use.

Weight loss injections that have not been licensed but are undergoing clinical trials include Ozempic, Mounjaro, Victoza, and Rybelsus. The table below shows each weight loss medication in more detail.

	Wegovy	Saxenda	Ozempic	Mounjaro	Victoza	Rybelsus
Active ingredient(s)	Semaglutide	Liraglutide	Semaglutide	Tirzepatide	Liraglutide	Semaglutide
Dosage	Gradually increases until the maintenance dose of 2.4mg	Gradually increases until the maintenance dose of 3mg	Gradually increases until the maintenance dose of 1mg	Gradually increases to a maximum dose of 15mg (for diabetes only)	Gradually increases to a maximum dose of 1.8mg (for diabetes only)	3mg, 7mg, or 14mg
What it’s approved for	Weight loss	Weight loss	Treating and managing type 2 diabetes	Treating and managing type 2 diabetes	Treating and managing type 2 diabetes	Treating and managing type 2 diabetes
How to take it	Pre-filled injectable pen, self-administered	Pre-filled injectable pen, self-administered	Pre-filled injectable pen, self-administered	Pre-filled injectable pen, self-administered	Pre-filled injectable pen, self-administered	Oral tablet
When to take it/Frequency	Once a week	Once daily, at the same time	Once a week	Once a week	Once a day	Once a day
Effectiveness*	Up to 89.8% after 6 months	67.5% after 12 weeks	66.9% after 24 months	85.1% on 5mg at 72 weeks	40.4% at 56 weeks	30-44% on 14 mg at 26 weeks
Is it prescription only?	Yes	Yes	Yes	Yes	Yes	Yes

* percentage of people that lost 5% or more of their initial body weight

Back to top

How do weight loss injections work?

All weight loss injections work in a similar way, depending on which active ingredient is used (liraglutide, semaglutide, or tirzepatide).

Liraglutide is a GLP-1 (glucagon-like peptide 1) agonist. It attaches to GLP-1 receptors, mimicking the hormone. By doing this, it controls hunger levels so you eat less without feeling hungry throughout the day. It also delays the emptying of your stomach, which helps you feel fuller for longer.

Semaglutide also works by mimicking GLP-1. This affects the parts of your brain responsible for hunger, sending a signal to your brain that you are full. It also controls blood sugar levels, which helps with cravings.

Tirzepatide is a GLP-1 agonist, meaning it works the same way as liraglutide and semaglutide by controlling hunger levels and cravings. It also imitates GIP (glucose-dependent insulinotropic peptide), a hormone released in the small intestine. This can improve how your body breaks down fat and sugars.

Back to top

How effective are weight loss injections?

Weight loss injections are effective when used alongside an exercise and diet regime. For instance, this study found that once-weekly semaglutide injections, such as Wegovy and Ozempic, can sustain and reduce body weight alongside lifestyle changes.

	% of people who lost 5% of their body weight
Diet and exercise alone	16.8 %
Mysimba	37.9 %
Orlistat	32.7 %
Ozempic	66.9 %
Saxenda	67.5 %
Wegovy	89.8%

All information in this table has been sourced here

How quickly will you see results?

You should start seeing results within a few weeks of taking weight loss injections and get the best effect with long-term use (12 weeks or more).

Your doctor will check your weight 12 weeks after you reach the maintenance dose. You should expect to see a weight loss of 5% or more of your initial body weight. Your doctor will stop the treatment and may suggest an alternative if you haven’t reached a 5% loss.

Which weight loss injection is the most effective?

Weight loss injections work differently depending on the person, but clinical studies have shown that Wegovy is the most effective. This does not mean that it will be the most effective for you, or your needs.

Saxenda

67.5% of people using Saxenda for 12 weeks or more lost at least 5% of their body weight. Several clinical trials have shown that Saxenda (liraglutide) is a safe and effective treatment for weight loss.

Wegovy

Wegovy has been found to achieve 5% or more initial body weight loss for up to 89.8% of patients after 6 months of use. As Wegovy is a relatively new medication, more research is needed into its effectiveness.

Ozempic

Ozempic has yet to be approved as a weight loss treatment in the UK. Clinical trials are underway, with one finding that 66.9% of patients with type 2 diabetes lost 5% or more of their initial body weight after 2 years of use. Further studies are needed to test the effectiveness of Ozempic solely for weight loss.

Back to top

Weight loss injections vs pills

All weight loss injections and most weight loss pills are prescription only, with a few exceptions. The weight loss pills currently available include:

orlistat (prescription only): An unbranded tablet containing the active ingredient orlistat. Each tablet helps your body to excrete around a third of the fat eaten at each meal instead of digesting it.
Xenical (prescription only): A branded version of orlistat, working in the same and allowing you to lose weight when taken with meals containing fat.
Mysimba (prescription only): A tablet containing bupropion and naltrexone hydrochloride, which work on the areas of your brain controlling hunger and energy levels.
Alli (over the counter medication): Also contains the active ingredient orlistat but in a lower dose than prescription orlistat and Xenical.

Which is more effective?

Both injections and pills can help with weight loss, but injections like Wegovy and Saxenda may be more effective as the medication does not need to be digested.

Tablets containing orlistat are only effective if you reduce your fat intake with each meal and can only be taken with meals containing fat.

Mysimba has a similar effect on the brain as weight loss injections, as it helps control appetite and hunger. In one study, Mysimba helped people lose weight, but there was a higher risk of side effects. For this reason, injectable weight loss treatments may be preferred, as the dosage is gradually increased to minimise side effects.

	% of people who lost 5% of their body weight
Diet and exercise alone	16.8 %
Mysimba	37.9 %
Orlistat	32.7 %
Ozempic	66.9 %
Saxenda	67.5 %
Wegovy	89.8%

All information included in this table has been sourced here.

Are side effects different?

Yes, side effects can vary between weight loss injections and pills. Common weight loss injection side effects include nausea (feeling or being sick) and vomiting, headaches, diarrhoea, or constipation. Mysimba has similar side effects.

Weight loss pills containing orlistat have different side effects because they affect fat digestion rather than the brain. Common orlistat, Xenical, and Alli side effects include fatty or oily stools, diarrhoea, and flatulence (farting).

	Weight Loss Injections	Weight Loss Pills
Nausea and vomiting (feeling or being sick)	x
Headaches	x
Diarrhoea or constipation	x	x
Fatty or oily stools		x
Flatulence (farting)		x

Back to top

Are weight loss injections safe?

Yes, weight loss injections are a safe treatment option. Your doctor will check your medical history and medications to make sure your chosen treatment option is suitable.

In this study, patients who used semaglutide for 2 years noticed substantial weight loss with only mild to moderate stomach upset.

The benefits of using weight loss injections to achieve a healthy weight often outweigh the mild to moderate side effects some patients experience. You can manage side effects at home, which usually improve as you continue your treatment.

Can I use weight loss injections if I’m pregnant or breastfeeding?

Weight loss injections are not recommended if you are pregnant or breastfeeding. It is not known if the medication in weight loss injections can be passed onto your baby. More research needs to be done into this.

Back to top

What are the side effects of weight loss injections?

Very common side effects of weight loss injections include:

nausea or vomiting
diarrhoea or constipation

Common side effects of weight loss injections include:

low blood sugar
dry mouth
pain, itching, irritation, or swelling at the injection site
gallstones
headaches
tiredness or weakness
a change in taste
heartburn or indigestion
bloating
wind
dizziness

Uncommon side effects of weight loss injections include:

skin rash
feeling unwell
dehydration
inflamed gallbladder
increased heart rate

If you notice these side effects, see if you can manage them at home. You should speak to your doctor if your side effects are severe or are not getting better after several weeks of treatment.

There are some rare but serious side effects to look out for when taking weight loss injections. If they happen, call 999 straight away or get someone to take you to A&E.

Rare side effects of weight loss injections include:

pancreatitis, which is an inflammation of the pancreas causing symptoms like nausea, vomiting, and severe stomach pains that do not go away
severe allergic reaction (anaphylaxis), which causes symptoms like difficulty breathing, swelling of the face, skin rash, and dizziness

Your dosage will be increased over several weeks to reduce the risk of side effects. If you get side effects, these will likely be mild and not bother you as much. You can manage side effects at home, as you usually would if you felt nauseous or constipated.

Which weight loss injection has the least side effects?

Side effects can vary from person to person. This is because some people may react differently, or even not at all, to the active ingredients in particular medications. For this reason, it's not possible to say that one weight loss injection has fewer side effects than another. Instead, the focus should be on finding a treatment that works for each individual person.

Back to top

Where can I buy weight loss injections?

If you meet the criteria for weight loss injections, you can order them online through Superdrug Online Doctor. You can also get some weight loss injections through the NHS. There are no over the counter weight loss injections.

Can you buy weight loss injections online?

Yes, through trusted and regulated online doctor services like Superdrug Online Doctor. This works just like your GP, except you don’t need to make an appointment or wait for a referral. Simply complete a short online form, which will be sent to one of our doctors.

A doctor will prescribe the medication if you are suitable for weight loss treatment. Your medication will be sent to your home in discreet packaging or you can collect it at your local Superdrug pharmacy.

Can you get weight loss injections over the counter?

No, weight loss injections contain active ingredients that should only be prescribed by a doctor.

Can you get weight loss injections on the NHS?

Yes, you can get weight loss injections on the NHS. You will usually need to be referred to a weight management specialist who might try other treatment options before suggesting weight loss injections.

Back to top

How can I get a prescription for a weight loss injection?

To be suitable for weight loss injections, you need to have:

a BMI (body mass index) of between 27 and 30 kg/m² (overweight) and a weight-related health condition, such as high blood pressure or diabetes

a BMI of greater than 30 kg/m² which is classed as obese

Guidelines also state that patients must follow a health and exercise plan set out by their doctor or a weight management specialist.

You cannot use a weight loss injection if you:

are allergic to the active ingredient, or any other ingredient in the injection
have severe heart failure
are over 75 years old* (there is not enough research into the use of weight loss injections at this age)
are already taking a similar medication for the management of type 2 diabetes
are pregnant or breastfeeding

*this does not apply to Wegovy

You should speak to your doctor if you take any medication, especially blood thinners like warfarin or other diabetic treatments.

People with kidney, pancreas, heart, liver, or thyroid problems should speak to their doctor before using a weight loss injection.

Back to top

Reviewed by: Dr Babak Ashrafi in line with the Superdrug Online Editorial Process.

GMC no. 6077866

Dr Ashrafi studied at King’s College London and specialises in cardiology, diabetes, and stroke medicine.

Last reviewed on: 14/08/23

Back to top

Sources

AJMC (2020). Efficacy of Oral Semaglutide: Overview of the PIONEER Clinical Trial Program and Implications for Managed Care: https://www.ajmc.com/view/efficacy-of-oral-semaglutide-the-pioneer-clinical-trial-program-and-implications-for-managed-care, retrieved 12/05/2023

EMC (2022). Saxenda 6 mg/mL solution for injection in pre-filled pen: https://www.medicines.org.uk/emc/product/2313/smpc, retrieved 12/05/2023

EMC (2022). Wegovy 1 mg, FlexTouch solution for injection in pre-filled pen: https://www.medicines.org.uk/emc/product/13801/smpc, retrieved 12/05/2023

JAMA Network (2015). Efficacy of Liraglutide for Weight Loss Among Patients With Type 2 Diabetes: https://jamanetwork.com/journals/jama/fullarticle/2428956, retrieved 12/05/2023

Mounjaro (2022). How to use Mounjaro: https://www.mounjaro.com/how-to-use-mounjaro, retrieved 12/05/2023

NatureMedicine (2022). Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial: https://www.nature.com/articles/s41591-022-02026-4, retrieved 12/05/2023

PubMed (2020). Naltrexone–bupropion (Mysimba) in management of obesity: A systematic review and meta‐analysis of unpublished clinical study reports: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7098870/, retrieved 12/05/2023

PubMed (2022). Real-world use of once-weekly semaglutide in patients with type 2 diabetes at an outpatient clinic in Spain: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9523693/, retrieved 12/05/2023

The New England Journal of Medicine (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity: https://www.nejm.org/doi/full/10.1056/NEJMoa2032183, retrieved 12/05/2023

The New England Journal of Medicine (2022). Tirzepatide Once Weekly for the Treatment of Obesity: https://www.nejm.org/doi/full/10.1056/NEJMoa2206038, retrieved 12/05/2023

Back to top

Weight Loss Injections

What are the different weight loss injections?

How do weight loss injections work?