By Caleb MorganUpdated November 2026
Naltrexone medication for weight loss is a prescription drug originally approved to treat opioid and alcohol dependence. When it is used for weight loss, it is usually paired with bupropion in a combined product, and it works by affecting appetite signals in the brain. It is prescription-only, so a doctor needs to evaluate whether it is appropriate for you.
Why Naltrexone Is Used for Weight Loss
Naltrexone blocks opioid receptors, which are involved in reward and craving. When paired with bupropion, the combination is thought to reduce the urge to eat in response to food cues and stress. The result is often a smaller appetite, not a change in metabolism. For more background, see Naltrexone for Weight Loss: A Beginner's Guide to How It Works.
Shopping for one? See our guide: 7 Best Weight Loss Exercises (2026): Beginner-Friendly Picks.
Results vary. Clinical trials of the combined product showed greater average weight loss than placebo over about a year, but many people lose less than the average, and some stop taking it because of side effects.
Factors That Affect Whether It Works for You
Several factors influence how well this approach works and whether it is safe for you:
- Your medical history. Naltrexone is not suitable for people taking opioid medications, those with uncontrolled high blood pressure, or those with certain seizure disorders.
- Your current medications. Tell your doctor about every prescription, over-the-counter drug, and supplement you take.
- Your eating habits and activity. Medication works best alongside a calorie-controlled diet and regular movement, not in place of them.
- Side effects. Common ones include nausea, constipation, headache, dry mouth, and trouble sleeping. Serious side effects are uncommon but need prompt medical attention.
For a broader comparison of options, read Best Weight Loss Medication: A Beginner's Guide to Options and Safety (2026).
What to Do If You Are Considering It
Start with a conversation with your doctor, not an online order. Bring a list of your current medications and your weight history. Ask whether you meet the usual criteria for weight-loss medication, which generally involve a higher body mass index or a lower BMI paired with a weight-related health condition.
- Ask your doctor whether naltrexone-bupropion is appropriate for your health profile.
- Set a realistic goal, such as 5 percent of body weight over six months, and track your weight weekly.
- Keep a simple food log for the first four weeks to notice patterns.
- Add a daily walk of 20 to 30 minutes, which you can build from Walking for Weight Loss: A Step-by-Step Guide for Beginners.
- Report side effects early. Many ease after the first few weeks, and your doctor can adjust the dose.
- Do not stop suddenly without checking with your doctor, and do not take extra doses to speed results.
Avoid products sold as “natural” alternatives to prescription weight-loss drugs. Most lack evidence and can carry their own risks. For a sense of what to look out for, see Wellness Products for Weight Loss: A Beginner's Guide to Choosing What Works.
FAQ
Is naltrexone medication for weight loss available without a prescription?
No. In the United States, the combined naltrexone-bupropion product requires a prescription, and a doctor should review your health history first.
How much weight can people lose on it?
In clinical trials, average loss was meaningful but varied widely between participants. Your results will depend on your starting point, diet, activity, and how well you tolerate the medication.
Who should not take naltrexone for weight loss?
People taking opioid medications, those with opioid dependence, uncontrolled high blood pressure, or certain seizure disorders should not use it. Pregnant or breastfeeding people should also speak with a doctor before starting any weight-loss medication. Consult a healthcare professional before starting any new medication.
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About Caleb Morgan
Caleb Morgan is part of our editorial team and reviews and edits our beginner fitness & weight-loss exercise guides, checking product details against manufacturer specifications and owner feedback.
