Quick answer
Does Mysimba work?
The clinical trial evidence shows that Mysimba produces modest but meaningful weight loss compared to placebo when used alongside dietary and lifestyle changes. It is not a dramatic result for everyone — roughly half of people in trials lost 5% or more of their body weight, while about half did not. Results vary considerably between individuals. It is a private prescription only medicine — not available over the counter and not funded by the NHS.
What the clinical trials show
The evidence behind Mysimba
Mysimba’s approval was based on four large randomised controlled trials: NB-301, NB-302, NB-303, and NB-304.
Average weight loss over placebo
Participants taking Mysimba lost a mean of 5.4% of their body weight, compared to 1.3% in the placebo group — an additional ~4 percentage points beyond placebo. For a person weighing 100 kg, that is roughly 4 kg more weight lost than placebo over the trial period.
Proportion reaching the 5% threshold
50.8% of people taking Mysimba lost at least 5% of their body weight, compared to 19.3% in the placebo group. The 5% threshold is the level clinicians typically regard as clinically meaningful for obesity-related health outcomes.
These figures reflect what was achieved in trial settings with lifestyle support alongside medication. If you do not lose at least 5% of your body weight by week 16, clinical guidance is to stop treatment.
What patients commonly report
Real-world experience: what people say
We do not publish star ratings or aggregate scores. What follows is a qualitative summary of commonly reported patterns.
Reduced appetite and cravings
Many people report that hunger feels less urgent, and that cravings for high-calorie foods become easier to manage. This tends to be the effect people notice first, often within the first couple of weeks.
Nausea in the early weeks
Nausea is the most commonly reported side effect, especially during the first two to three weeks. Most people find it improves as the body adjusts, though for some it persists and leads to stopping the medication.
Results vary considerably
Some people lose noticeably more than the trial average; others lose very little. Age, starting weight, how closely dietary changes are followed, and individual biology all affect the outcome.
Works better alongside dietary change
People who make meaningful changes to their diet while taking Mysimba tend to see better outcomes than those who rely on the medication alone. Mysimba is designed as an adjunct to lifestyle changes, not a replacement.
Some stop early due to side effects
A proportion of people discontinue before 16 weeks, primarily because of nausea, headache, or difficulty tolerating the titration schedule. The slow dose build-up is intended to reduce this but does not eliminate it.
Weight regain after stopping
Like most weight-loss medications, stopping Mysimba without maintaining dietary and lifestyle changes can lead to weight regain over time.
Who it tends to suit
Who is most likely to benefit?
People who may do well
Those who have struggled with hunger and cravings as the main barrier to losing weight. People with BMI 30 or above, or BMI 27 or above with a weight-related condition, who have no contraindications and are willing to make dietary changes alongside the medication.
People for whom it may not be suitable
Those with a history of seizures, eating disorders, current opioid use, uncontrolled high blood pressure, or bipolar disorder cannot take Mysimba. It is also not the right choice if you are unwilling or unable to make dietary changes alongside medication.
Remember
Private prescription only — not available on the NHS
Mysimba is available in the UK on a private prescription only. A clinical assessment is required before any prescription can be issued. Do not purchase from any source that does not require a valid prescription.
Getting started
Where to get a Mysimba prescription in the UK
A number of CQC-registered and GPhC-registered online prescribing services offer private Mysimba consultations, including Chemist4U, ZAVA, Click Pharmacy, NowPatient, and PrivateDoc, among others. Costs typically range from £99 to £200 per month including consultation. Always verify registration before using any service.
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FAQ
Common questions about Mysimba results
How much weight will I lose on Mysimba?
There is no reliable way to predict your individual result. In the clinical trials, the average weight loss was 5.4% of starting body weight with Mysimba, compared to 1.3% with placebo. Roughly half of participants lost 5% or more. Diet and lifestyle changes alongside the medication influence the outcome significantly.
How quickly does Mysimba start working?
Appetite effects may become noticeable within the first few weeks, but meaningful weight loss usually takes longer. The standard clinical assessment point is 16 weeks — if you have not lost at least 5% of your body weight by then, the guidance is to stop treatment.
Will I put weight back on when I stop taking Mysimba?
Weight regain after stopping is common with all weight-loss medications if dietary and lifestyle changes are not maintained. Mysimba does not permanently alter how your body regulates weight.
Related pages
Mysimba UK guide
How it works, who it is for, cost, and how to get a private prescription. Read the full guide.
Side effects and safety
Nausea rates, rare risks, contraindications, and what to tell your prescriber. Read the safety page.
Important
Information only
Tablet Compare is information only. Mysimba is a prescription-only medicine requiring clinical assessment. Speak to a registered clinician before starting any treatment. Avoid unregulated sellers.