Taking naltrexone and Wegovy at the same time

Step 1: Understand what each medicine actually does

Wegovy works by mimicking GLP-1, a gut hormone that signals fullness to the brain and slows the rate at which the stomach empties. Given as a weekly injection, it reduces appetite steadily over months. The STEP 1 trial, published in the New England Journal of Medicine, showed an average weight reduction of around 15% over 68 weeks at the 2.4 mg maintenance dose. You can read a fuller account of how semaglutide works on the semaglutide overview.

Naltrexone is a different animal entirely. It binds to and blocks opioid receptors. At standard doses it is used to support recovery from alcohol or opioid dependence. At lower doses, combined with bupropion in a tablet called Mysimba, it is licensed in the UK as a weight-management medicine. On its own (without bupropion) naltrexone is not licensed for weight loss in the UK, though it is sometimes prescribed off-label. That distinction matters when you are researching this combination, and our dedicated page on naltrexone and Wegovy together goes into greater detail on what the evidence currently shows.

Because the two medicines act on separate systems, prescribing both is not inherently contradictory. The question is whether the combination is appropriate for your specific situation.

Step 2: Recognise the practical interactions to discuss with your prescriber

There is one interaction that always needs flagging: Wegovy slows gastric emptying, and this can alter how quickly oral medicines are absorbed. Naltrexone is taken by mouth. A slower journey through the stomach may shift the timing and peak concentration of naltrexone, even if the total amount absorbed remains similar. The NHS medicines page for semaglutide notes that interactions with other oral medicines are possible for this reason, and the advice is to tell your prescriber about every oral medicine you take before starting Wegovy.

The second practical point concerns pain management. Naltrexone blocks opioid receptors completely; while it is active, opioid-based analgesics will not provide effective pain relief. If you are on naltrexone and need surgery or urgent pain treatment, your anaesthetist and treating team must know. NHS England's guidance on weight-management injections similarly advises telling your anaesthetist about any relevant medicines before any procedure, that principle applies here regardless of which of the two medicines you are taking.

A common misconception is that because both medicines can contribute to weight loss, combining them doubles the benefit. The reality is more nuanced. Benefit and risk both need to be weighed by a prescriber who can see your full medical history.

Step 3: Map the overlapping side effects so you can report them clearly

Nausea is the most frequently reported side effect of Wegovy, particularly in the first weeks of treatment or after a dose increase. Nausea and vomiting are also listed side effects of naltrexone. If you are taking both and feel sick, neither you nor a pharmacist can reliably attribute it to one medicine without context. Keeping a brief symptom log (when nausea arrives relative to your Wegovy injection day and relative to when you take naltrexone) gives your prescriber genuinely useful information.

Other side effects to be aware of across both medicines include headache, fatigue, and abdominal discomfort. Wegovy's side-effect profile is primarily gastrointestinal. Naltrexone can also cause sleep disturbance, anxiety, and in rare cases liver enzyme changes at higher doses, so liver function monitoring is sometimes part of naltrexone prescribing. None of this is a reason to avoid either medicine if your prescriber considers them appropriate; it is a reason to understand what you are taking and why. If you notice symptoms that concern you, the MHRA Yellow Card scheme allows patients to report suspected side effects directly.

For a closer look at how Wegovy fits into a broader weight-loss plan, the Wegovy treatment guide covers eligibility, the licensed schedule, and what to expect during treatment. Questions about cost context are addressed on the Wegovy cost page. And if you are curious about how alcohol interacts with semaglutide more broadly, the Wegovy and alcohol page covers what is currently known.

Step 4: Get both medicines properly reviewed before starting

Neither Wegovy nor naltrexone should be started without a full clinical assessment. If you are already taking naltrexone for dependence and are considering Wegovy for weight management, the right route is to tell whichever clinician is managing your naltrexone, and to be transparent with the prescriber assessing you for Wegovy. The two conversations need to happen together, not in parallel silos. It is also worth reading up on whether Wegovy is classed as a specialty drug, as this can affect how it is prescribed and accessed depending on your circumstances.

If you are considering Mysimba (the naltrexone-bupropion combination licensed for weight loss) alongside Wegovy, the interaction picture becomes more complex still, because bupropion adds its own set of interactions. Your prescriber needs the complete list.

At nume, every consultation is read by a GPhC-registered Independent Prescriber (a real clinician, not software) on the day you submit it. Our prescribers ask about your current medicines precisely because combinations like this one need individual assessment. If you are ready to talk through your situation, start your free consultation and we will take it from there.