How Long Do Mysimba Side Effects Last?

When researching the most suitable weight loss medication for you, the potential impact of side effects is one of the most important factors. Each treatment has different active ingredients and mechanisms of action, and may react differently to other medications you’re currently taking, meaning it’s essential to have a clear understanding of what you could expect.

Mysimba is no exception. Unlike better-known treatments like Mounjaro and Wegovy, Mysimba comes in tablet form, making it a strong option for someone who doesn’t like injections. It also contains two active ingredients that work in tandem to curb cravings and reduce food intake.

But what about the side effects of this medication? In this article, we’ll explore the various aftereffects of Mysimba, how to tackle them, and answer the question “How long do Mysimba side effects last?” Let’s get started. 

START YOUR MYSIMBA CONSULTATION TODAY

What are the Side Effects of Mysimba?

All medications, including Mysimba, can cause side effects. The most common side effects are gastrointestinal symptoms, such as feeling or being sick (nausea or vomiting), constipation, and headaches. Most of these side effects occur at the beginning of treatment as your body gets used to the active ingredients and can usually be managed at home.

Other common Mysimba side effects include:

• anxiety
• dizziness
• shakiness
• sleep issues
• taste changes
• difficulty concentrating
• tiredness
• fast or irregular heartbeat
• hot flushes
• irritability
• sweating
• stomach pain

Uncommon Mysimba side effects include:

• hives
• mood changes
• balance issues
• hypersensitivity
• memory loss
• motion sickness
• abnormal dreams

For a more detailed explanation of Mysimba side effects, check the patient information leaflet (PIL) enclosed with the medication.

How to Determine the Duration of Mysimba Side Effects

Mysimba side effects vary from person to person. Some people experience side effects after the first dose, while others may not notice any until their Mysimba dosage is increased. Not everyone who takes Mysimba will get side effects.

Several factors can affect the duration of Mysimba side effects, including how long the medication stays in your system, any other drugs you take, your age, and any underlying health conditions you may have. 

Factors that Influence the Duration of Mysimba Tablets Side Effects

Various factors can influence how long Mysimba side effects will last. These include:

• Medication Half-Life: Understanding Mysimba's half-life can help predict how long its side effects will last. The term ‘half-life’ refers to the time it takes for 50% of a medication to be eliminated from the body. Mysimba’s half-life differs by active ingredient: Bupropion lasts 21 hours, and Naltrexone lasts 5. As the active ingredients leave your body, the side effects of Mysimba should start to improve.  
• Pre-existing Medical Conditions: Some conditions, such as kidney or liver issues, can prolong Mysimba's time in your system, potentially increasing the duration and severity of side effects.
• Other Medications: Certain medications can interact with Mysimba and vice versa, which may increase the likelihood of side effects or potentially make them worse.
• Age: Age-related changes in the body’s ability to process and metabolise medication can make you more sensitive to side effects. For example, people over 65 may be more likely to experience central nervous system side effects, such as dizziness and shaking. Gastrointestinal side effects can also be a common reason for older people to stop taking Mysimba.
• Incorrect Dosing: Missing Mysimba doses or taking too much can increase your risk of side effects. If you take more Mysimba than prescribed, speak to a doctor immediately or go to A&E.

Long-Term Side Effects of Mysimba

The long-term side effects and safety of Mysimba are not fully known. Although most of the common side effects, like nausea, constipation, and headaches, are short-term and tend to improve as your body gets used to the medication, there may be some long-term consequences, like cardiovascular issues.

Research suggests that there are no long-term cardiovascular side effects if you take Mysimba for a year. Still, there is no conclusive evidence about cardiovascular safety beyond this point. If you have not lost at least 5% of your body weight after 1 year, a clinician will tell you to stop taking Mysimba. A clinical study investigating the long-term effects of Mysimba on the heart is expected to announce its results in 2028.

Mysimba

Rated 1.0 out of 5 based on 1 reviews

Rated 1.0 out of 5 based on 1 reviews

• Reduces cravings & emotional eating 
• Convenient, twice-daily oral treatment 
• Proven weight loss results

• Discreet delivery next working day
• Online prescription - No doctor visit

Prices from £109.99 Review More Prices

Start Order More Info

Get Started

Start Order More info

Potentially Serious Mysimba Side Effects

There are some potentially serious side effects of Mysimba, which, if you get them, need immediate medical attention. If you notice any of these side effects, it could be a sign of something more serious and requires immediate medical attention:

• Suicidal thoughts: There have been reports of depression, suicidal thoughts, and suicide attempts during Mysimba treatment.
• Loss of consciousness or seizures: Can affect up to 1 in 1,000 people. They are more likely to occur if you take too many tablets, take other medications at the same time, or are at a higher risk of having seizures.
• Erythema multiforme: Red, itchy spots on the limbs, which can affect the mouth and other parts of the body.
• Rhabdomyolysis: An abnormal breakdown of muscle tissue that causes severe muscle cramps, muscle pain, and weakness.
• Serotonin syndrome: A condition that causes changes in your mental status, including hallucinations, agitation, and coma, as well as high temperature, blood pressure, and gastrointestinal issues.
• Lupus: An autoimmune disorder that affects the skin and organs.

How to Manage the Side Effects of Mysimba

Many of the most common side effects of Mysimba, like nausea, constipation, and headaches, are mild, temporary, and can be managed at home through a variety of self-care measures. Side effects often improve as your body adjusts to the medication over a few weeks.

Some of the common side effects and the ways you can manage them include:

• Feeling and being sick: Take the Mysimba tablets with food and eat smaller, more frequent meals. Stick to bland foods, like crackers, and avoid spicy, greasy, or fatty foods.
• Headaches: Drink plenty of water to stay hydrated, get some rest, and take over-the-counter painkillers, such as paracetamol and ibuprofen. 
• Dizziness: Where possible, sit or lie down until the feeling passes and avoid driving or operating machinery if Mysimba makes you feel dizzy.
• Sleep issues: Take your evening Mysimba dose before dinner rather than at bedtime. Practice good sleep hygiene by keeping to a consistent sleep schedule, turning off screens 1 to 2 hours before bed, and keeping the room calm, cool, and quiet.
• Constipation: Increase your fibre intake by choosing foods like fruit, vegetables, and wholegrains. Drink plenty of water throughout the day and speak to your clinician about taking laxatives.

Although most side effects of Mysimba are manageable, if you find them challenging or are concerned about them, you should contact your clinician for more advice. 

Side Effects of Mysimba: Frequently Asked Questions

Mysimba, like all weight loss medications, can cause side effects. The most common are usually gastrointestinal and usually improve as your body gets used to the medication. However, you may have questions about the safety of Mysimba and its active ingredients, so we’ll shed some light on these key concerns here to help you make a more informed choice about your weight loss treatment.

Is Mysimba Dangerous?

Mysimba is considered safe for most people when it is taken correctly and under medical guidance, but it does carry some risks and can cause side effects, some of which can be serious. Mysimba is a prescription-only medication, and a clinician will assess your suitability before prescribing it. 

What are Potential Bupropion Side Effects?

Bupropion is an antidepressant and can cause a range of potential side effects, including common and rare types. Very common side effects include sleep issues, while common ones include feeling depressed, anxious, or agitated, difficulty concentrating, headaches, shakiness, feeling or being sick, and stomach pain.

What are Potential Naltrexone Side Effects?

Naltrexone is a prescription opioid antagonist that is used to treat addiction. Common side effects include feeling or being sick, stomach pain, anxiety, nervousness, trouble sleeping, headache, and joint or muscle pain. It is well tolerated, with side effects often mild and usually improving as your body adjusts.

How Much Mysimba Should I Take?

Mysimba follows a dosage schedule that gradually increases over 4 weeks, reaching a maximum of 2 tablets twice a day. It is important that you follow the dosage schedule and take Mysimba exactly as your clinician has instructed, to ensure you take it safely.

The dose is increased over this time to help manage potential side effects and allow your body to adjust to naltrexone and bupropion slowly. Taking the tablets with food also helps minimise stomach irritation and digestive side effects, reducing the risk of nausea and headaches. 

Mysimba

Rated 1.0 out of 5 based on 1 reviews

Rated 1.0 out of 5 based on 1 reviews

• Reduces cravings & emotional eating 
• Convenient, twice-daily oral treatment 
• Proven weight loss results

• Discreet delivery next working day
• Online prescription - No doctor visit

Prices from £109.99 Review More Prices

Start Order More Info

Get Started

Start Order More info

Take the First Steps to a New You

If you’re looking to lose weight but have found it difficult to do so when relying solely on a healthy diet and regular exercise, a medicated weight loss programme with Prescription Doctor may be the solution. We offer a range of treatments, including Mysimba, Mounjaro, Wegovy, and Nevolat.

Our consultation service is simple and straightforward to navigate. With us, there’s no need for lengthy waiting times or potentially awkward face-to-face meetings. Instead, just complete a brief online questionnaire, and our experienced clinicians will review your information to determine whether your chosen treatment is suitable for your circumstances. If not, an alternative may be recommended.

Convenience is a core part of service, which is why we deliver your items to your door in discreet packaging. Orders approved before 3pm on a weekday are also dispatched for next-day delivery, so you can access your treatment quickly.

We’re here to support you at every stage of your weight loss journey. Our clinicians are available to answer any medical queries and will regularly check in with you to monitor progress and ensure everything is working as intended. You can also find a library of useful information about the various treatments we offer on our website.

Ready to begin? Start your weight loss consultation with Prescription Doctor today and let us support you throughout your journey. 

Authored By

Leanne Edermaniger

Medical Content Writer

Leanne is a science and health content writer focusing on human health and biology while utilising her solid academic background.

Published on: 23/10/2023 Re-Published on: 22/01/2026

Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist

Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Reviewed on: 22/01/2026