Several prescription weight-loss medicines are now available in the UK. These include OrlistatOzempicSaxenda and Mysimba. Although these medicines are used for weight loss, they contain different active ingredients and work in different ways. In this article, we take a closer look at Saxenda and Mysimba and how they differ from each other.

Comparing Saxenda and Mysimba

Saxenda Mysimba
Active Ingredient Liraglutide Naltrexone and bupropin
How it works Regulates appetite and makes you feel full and less hungry Works on areas of the brain controlling food and energy use
How it’s used Injected once daily Tablets taken daily (max dose two tablets twice daily)
Price £47/per pen £117.99 for 112 tablets
Who it’s for People with a BMI over 30, or a BMI over 27 with weight related diseases People with a BMI over 30, or a BMI over 27 with weight related diseases
Common side effets Nausea, diarrhoea, constipation, vomiting Nausea, vomiting, constipation, headache
Week 1 One tablet in the morning
Week 2 One tablet in the morning, one tablet in the evening
Week 3 Two tablets in the morning, one tablet in the evening
Week 4 Two tablets in the morning, two tablet in the evening


What is Saxenda?

Saxenda is a prescription-only medicine that can be prescribed in the UK as a weight-loss treatment. It’s available for people with a BMI of 30 or higher, or for people with a BMI above 27 who have a weight-related medical condition. This includes diseases such as type 2 diabetes, high blood pressure and sleep apnea.

Saxenda contains the active ingredient liraglutide. Saxenda is injected once daily and helps to make you feel more full and less hungry. It should be used alongside a calorie-controlled diet and exercise to help with weight loss. You can find further information about understanding calories and exercise guidelines from the NHS website.

The active ingredient, liraglutide, can also be used as a long term medicine in people with type 2 diabetes. This means that Saxenda can cause low blood sugar as a potential side effect.

How Saxenda works

The active ingredient, liraglutide, is very similar to a hormone produced by our body called glucagon-like peptide-1 (GLP-1). This hormone is released from the intestines after we eat. Liraglutide acts on areas of the brain that control appetite.

By acting on these areas of the brain, Saxenda helps to make you feel full and less hungry. This can lead to you eating less and losing weight. Used alongside a calorie-restricted meal plan and increased physical exercise, this can be an effective weight-loss treatment.

How to use Saxenda

Saxenda is injected under the skin (subcutaneously) once daily. The best areas to inject are the front of your waist, your upper arm, or the front of your thighs. You can see more details and diagrams at the end of the patient information leaflet.

When you first start taking Saxenda, the starting dose is 0.6mg once daily. The dose is gradually increased week by week until you reach the recommended dose of 3.0mg once daily. You can inject Saxenda at any time of the day.

How to store Saxenda

You should store your Saxenda pen(s) in the fridge as soon as you get them. Once you start using a pen, you can keep it for 1 month stored below 30°C. When storing the pen, keep the cap on to protect it from light. Saxenda pens should not be frozen.

Saxenda price

At Simple Online Pharmacy, you can buy a single 3ml Saxenda pen for £51. The price per pen decreases if you buy more pens. For example, 3 pens are £150 and 10 pens are £470 (only £47 per pen). You can also buy replacement needle heads and sharps bins when you buy Saxenda pens from us.

Prescription weight loss treatments available today

If you’d like to buy more replacement needles, you can see our Saxenda needles page.

Saxenda reviews

clinical trial conducted over 56 weeks comparing Saxenda to a placebo injection showed that patients had better weight loss results using Saxenda. It found that 92% of patients using Saxenda lost weight compared to 65% of patients using placebo.

The study found that in patients taking Saxenda:

  • 14% of people lost 15% or more of their body weight
  • 33% of people lost 10% or more of their body weight
  • 63% of people lost 5% or more of their body weight

You can read Saxenda reviews on Please note that these reviews may be written by US patients and may not be Saxenda UK reviews.


Mysimba is another prescription-only medicine that’s licensed in the UK for weight loss. It can be prescribed to people with a BMI of 30 or higher, or for people with a BMI above 27 who have a weight-related medical condition. Examples include high blood pressure, type 2 diabetes and high cholesterol. It should be used alongside a reduced-calorie diet and increased physical activity.

Mysimba contains two active ingredients: bupropion and naltrexone. Mysimba tablets are taken orally every day. The tablets are prolonged-release, which means the medicine is slowly released in the body.

The brand name for this medicine in the US is Contrave. Contrave, in the UK, is branded as Mysimba.

How Mysimba works

Although the combination of naltrexone and bupropion in Mysimba has been shown to be effective, it’s not known exactly how Mysimba works. It’s thought to work on the parts of the brain that control food cravings and intake and energy expenditure.

Not everyone can take Mysimba. People with certain conditions should not take this medicine. This includes people who suffer from seizures, have abnormally high blood pressure, or have severe liver disease.

How to use it

Mysimba is taken every day. The starting dose is usually one tablet once a day. This is gradually increased up to the maximum recommended dose of two tablets twice a day. The tablets should ideally be taken with food.

Treatment with Mysimba should be stopped after 16 weeks if you have not lost at least 5% of your initial body weight. Consult your doctor for more advice after taking this medicine for 16 weeks.

Mysimba price

Each pack of Mysimba contains 112 tablets. The first pack will last just over 5 weeks as you gradually increase the daily dose. Once you reach the maximum recommended dose, a pack of 112 tablets will last 4 weeks.

At Simple Online Pharmacy, we offer Mysimba at £117.99 per pack.

Mysimba reviews

In 3 clinical studies, patients taking naltrexone and bupropion achieved statistically and clinically significant weight loss when compared with placebo. This weight loss continued throughout the 56 week studies.

In each study, the number of patients who lost 5% or more of their body weight with naltrexone and bupropion was over 60%. Over 30% of patients taking naltrexone and bupropion in each study lost 10% or more of their body weight.

You can see user reviews for Contrave on Contrave is the US brand name for Mysimba.