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Authored on 17 April 2026 by Dr Ruch Karunadasa,
Medically reviewed 27 April 2026 by Mr Adeel Arshad.
Next review due: 27 April 2027
Mysimba (naltrexone & bupropion) — prescription weight-loss tablets.
Mysimba is a prescription-only weight-loss medication. You take 1–2 tablets once or twice a day up to a maximum of 4 tablets per day. Bupropion helps reduce your appetite; naltrexone is thought to curb food cravings. Mysimba is used alongside an active lifestyle and a calorie-controlled balanced diet, and exercise helps you maintain a healthy weight when you stop treatment.
Part of our weight loss treatment planThis page provides factual information about Mysimba (naltrexone and bupropion) for educational purposes. This is not an advertisement. A prescription will only be issued following a successful clinical assessment by our healthcare team.
* Your eligibility for our treatment plan will be assessed by a clinical professional following a consultation.
Mysimba has two active ingredients that, although not fully understood, are thought to be complementary in the way they work. Bupropion helps to reduce your appetite so that you do not feel as hungry and are satisfied with less food. Naltrexone is thought to curb your food cravings which reduces your desire to eat. The combination of these two actions works together to help you lose weight.
Although Mysimba is shown to be effective as a weight-loss treatment and was approved for use in Europe in 2015, it does not have a license for this use by the NHS in the UK so is only available on a private prescription.
Mysimba packs start from £109
Mysimba costs around £1.25 per tablet including delivery and prescription and comes in packs of 112 tablets. See Mysimba cost and pack size
Mysimba can only be used as a weight-loss treatment if you have previously tried and failed to lose weight through diet and exercise alone.
Your medicine should be taken as advised by us. When you take Mysimba you will gradually increase your dose over a four-week period until you reach what is called the maintenance dose. This is the dose at which you will continue to take Mysimba. You increase your dose as follows:
You should swallow your tablets whole with plenty of water, with or immediately after food. They are a prolonged-release formulation, so you must never crush, chew or cut the tablets as this will affect the rate at which the active ingredients are released into your body.
The maximum recommended dosage of Mysimba is two tablets twice a day. If you do not lose at least 5% of your body weight after 16 weeks of treatment, your doctor will evaluate if you should continue taking Mysimba.
Always take this medication exactly as your doctor tells you to. You can find full details in the patient information leaflet. Additional information and guidance on Mysimba can also be found at www.mysimba.co.uk.
Mysimba is a prolonged release tablet which is blue in colour. The tablets are round and have NB-890 embossed on one side.
Mysimba cannot be used if:
Mysimba should be used in caution if:
You must tell us about all the medications that you are taking including those that are prescribed, bought over the counter and also herbal remedies and supplements as they may interact with Mysimba and you will need to be monitored for side effects
As with all medication, Mysimba can be associated with unwanted side effects. Although generally mild some of these can be more severe which may result in the treatment being discontinued.
Very common side effects (may affect more than 1 in 10 people):
Common side effects (may affect up to 1 in 10 people):
Uncommon side effects (may affect up to 1 in 100 people):
There are further rare and very rare side effects that occasionally people can experience when taking Mysimba, for complete details about all side effects always read the Patient Information Leaflet.
Answers to common questions about Mysimba and our weight loss programme.
Mysimba pricing depends on the pack you choose and is shown on this page (starting price appears above the price table).
Mysimba costs around £1.25 per tablet including delivery and prescription and comes in packs of 112 tablets.
Mysimba can only be used as a weight-loss treatment if you have previously tried and failed to lose weight through diet and exercise alone.
Your medicine should be taken as advised by us. When you take Mysimba you will gradually increase your dose over a four-week period until you reach what is called the maintenance dose.
You should swallow your tablets whole with plenty of water, with or immediately after food. They are a prolonged-release formulation, so you must never crush, chew or cut the tablets as this will affect the rate at which the active ingredients are released into your body.
The maximum recommended dosage of Mysimba is two tablets twice a day. If you do not lose at least 5% of your body weight after 16 weeks of treatment, your doctor will evaluate if you should continue taking Mysimba.
Mysimba cannot be used if you are pregnant, breastfeeding, under 18 or over 75, have relevant allergies, severe liver disease, end-stage kidney disease, uncontrolled hypertension, seizures, certain mental health conditions, use of MAOIs or opiates, or other medicines that interact. We also need caution in several situations such as age 65–75, liver or kidney problems, depression, diabetes, heart disease, alcohol or sedative use, and medicines that lower seizure threshold.
You must tell us about all the medications that you are taking including those that are prescribed, bought over the counter and also herbal remedies and supplements as they may interact with Mysimba and you will need to be monitored for side effects.
How long a pack lasts depends on your titration stage and whether you are on a starter or continuation pack (112 tablets). Your prescriber will explain how dosing maps to pack duration.
As with all medication, Mysimba can be associated with unwanted side effects. Although generally mild some of these can be more severe which may result in the treatment being discontinued.
Very common side effects (may affect more than 1 in 10 people): insomnia; anxiety and agitation; headache; feeling restless; abdominal pain and constipation; nausea and vomiting; joint and muscular pain.
The full lists of common, uncommon, rare and very rare side effects are set out earlier on this page and in the Patient Information Leaflet. Always read the PIL for the complete list.
Whilst on any of our prescription weight loss treatments we recommend following a calorie controlled diet to support your goals. As this can be a confusing area with lots of mixed messaging, we partnered with leading nutritionist Glen Matten to bring to you our very own PrivateDoc diet guide.
While many online retailers claim to supply genuine medicines, they may be unregulated, provided without a genuine doctor consultation and potentially very dangerous. You can rest assured, PrivateDoc is a fully registered digital health service. We have UK registered doctors that review and assess every consultation. All the medicines we supply are 100% genuine and fully regulated by the Medicines and Healthcare products Regulatory Agency (MHRA).
Saxenda is an injectable GLP-1 treatment; Mysimba is an oral tablet combining naltrexone and bupropion with a different mechanism. Suitability depends on your medical history and goals.
Interested in finding out how your Mysimba weight loss treatment travels and arrives to you? Check out this video to view our treatment unboxing to know what to expect once your treatment is approved and shipped.
Yes. Exercise and healthy eating should be part of your weight loss programme alongside any prescribed medication. Build activity gradually according to your current fitness level.
PrivateDoc is happy to introduce you to some of our leading UK licensed clinicians who will be supporting you through your weight loss journey
