Topiramate for weight loss: how it works and results

Topiramate is a seizure and migraine medicine, and weight loss is one of its most common side effects. That has led to interest in using it for weight loss, and a 2023 review lists weight loss among its common off-label uses.

Read on to find out what the FDA labels and clinical trials actually show, how topiramate compares with Qsymia and GLP-1 medicines, and the risks you should know.

Before you start either medicine, read the full Topamax Prescribing Information and Qsymia Prescribing Information, including the warnings.

Is topiramate approved for weight loss?

No, topiramate on its own is not FDA-approved for weight loss. Topamax is approved to treat certain seizures in people 2 and older and to prevent migraines in people 12 and older. Using it for weight loss is "off-label," which means a doctor prescribes it for a use the FDA hasn't approved.

Weight loss shows up as a side effect in Topamax's own trials. In pooled migraine studies, mostly in adults, 9% of people taking 100 mg a day reported weight loss, compared with 1% on a placebo (a pill with no medicine).

Large trials of topiramate for obesity ran in the early 2000s.The sponsor, Johnson & Johnson, stopped several of these trials early so it could develop a controlled-release version instead. That version was never approved for weight loss..

Topiramate alone was never approved for weight loss. In 2012, the FDA approved Qsymia, which combines topiramate with another medicine, phentermine.

How does topiramate help with weight loss?

No one knows exactly how topiramate helps with weight loss. According to the Qsymia label , it may lower appetite and help people feel full sooner,likely through several effects on brain chemicals and nerve signaling.

Phentermine, the other medicine in Qsymia, is a stimulant similar to amphetamine that likely reduces appetite and how much people eat. Qsymia is a controlled substance, which means its prescribing and use are more tightly regulated.

How much weight do people lose on topiramate?

In clinical trials, people taking topiramate alone lost about 5% to 10% of their body weight, depending on the dose and the length of treatment. People taking a placebo lost about 2% to 3%. Everyone in these trials also followed a structured diet, exercise, or lifestyle program.

A 2011 review combined 10 trials with 3,320 people. On average, people taking topiramate lost about 12 pounds (5.34 kg) more than people taking a placebo. Trials that lasted longer than 28 weeks showed more weight loss.

You may see claims that topiramate led to weight loss of up to 16.5%. That number comes from a 2004 trial with an unusual design. Everyone first followed an 8-week low-calorie diet, and only people who lost at least 8% of their weight went on to take topiramate or a placebo.

After another 44 weeks, people on topiramate had lost 15.4% to 16.5% of their starting weight, counting the diet. People on the placebo had lost 8.9%. So topiramate added about 6.5 to 7.6 percentage points on top of the diet.These figures include only the 293 people who completed 44 weeks.

How does topiramate compare with Qsymia and GLP-1 medicines?

In trials, topiramate alone led to similar or less weight loss than Qsymia, and less than today's GLP-1 medicines. The numbers below come from different trials, so they aren't a direct, head-to-head comparison.

In Qsymia's 2 main trials, 67% to 70% of people on the top dose lost at least 5% of their weight after about a year. But many participants stopped early: 40% of everyone in one trial and 31% in the other dropped out before the end. To learn about GLP-1 options, see our guides to Wegovy® and Zepbound®.

What is the normal dose of topiramate for weight loss?

There is no standard, FDA-approved dose of Topamax for weight loss, because it isn't approved for that use. If a provider prescribes it off-label, they choose and adjust the dose for you.

In weight-loss trials, people took 64 to 384 mg of topiramate (Topamax) daily, and higher doses caused more side effects. For comparison, the Topamax label's dose for migraine prevention is 100 mg a day, taken as 50 mg twice a day.Treatment starts at 25 mg each evening for the first week and the daily dose is increased by 25 mg each week until it reaches 100 mg by week 4..

Qsymia, the approved medicine, has a set dosing plan on its label:

• Start: 3.75 mg phentermine and 23 mg topiramate once a day for 14 days, then 7.5 mg/46 mg.
• Check at 12 weeks: If you've lost less than 3% of your weight, the label says to raise the dose to 15 mg/92 mg, stepping up over 14 days.
• Stop if it isn't working: If you've lost less than 5% after 12 weeks on the top dose, the label says to stop. The medication must be tapered, not stopped all at once.

Timing differs too. Topamax can be taken with or without food. Qsymia should be taken in the morning, because an evening dose can cause trouble sleeping.

Why am I not losing weight on Topamax?

You may not be losing weight on Topamax because it doesn't cause weight loss in everyone. In migraine trials, mostly in adults, only 9% of people taking 100 mg a day reported weight loss as a side effect.Those trials weren’t designed to measure weight loss though.

Even in weight-loss trials, results varied a lot. In the largest one, about half of the participants on 96 mg a day had lost at least 5% of their weight after 60 weeks, and the rest lost less. The Qsymia label also recognizes that some people won't respond.It says to stop Qsymia, tapering off gradually, if you haven’t lost at least 5% of your starting weight after 12 weeks on 15 mg/92 mg, the highest dose.Diet and activity can also affect your weight. Talk to your provider before changing your dose, since they can check for other causes or discuss FDA-approved options. Our guide on why you might not be losing weight covers common causes.

What are the side effects and risks of topiramate?

The most common side effects of topiramate are tingling in the hands and feet, changes in taste, and trouble with memory, focus, or word-finding. In weight-loss trials, people on topiramate were about twice as likely as those on a placebo to stop treatment because of side effects. In one trial, 21% stopped for this reason, compared with 11% on a placebo.

The Topamax label also lists serious risks:

• Sudden eye problems: Topiramate can cause sudden nearsightedness and acute angle-closure glaucoma, in which the eye’s drainage angle suddenly closes and eye pressure rises. Without fast treatment, this can lead to permanent vision loss. Signs include blurred vision or eye pain, usually within the first month.Topiramate can also cause loss of side (peripheral) vision.
• Too much acid in the blood: Called metabolic acidosis, this can happen at any time during treatment. The label recommends a blood test for bicarbonate (a measure of acid balance) before starting and regularly during treatment.
• Kidney stones: The label recommends drinking plenty of fluids to help prevent them.
• Suicidal thoughts and mood changes: Seizure medicines like topiramate nearly double the risk of suicidal thoughts or actions. In pooled studies of these medicines, the rate was 0.43% compared with 0.24% on a placebo.
• Slowed thinking: The label urges caution when driving or using machinery.
• Less sweating and overheating: This happens most often in children.
• Birth defects: Taking topiramate early in pregnancy raises the risk of cleft lip or cleft palate.
• Serious skin and allergic reactions: Rare but severe rashes, swelling of the face or throat, and whole-body allergic reactions can occur.

Topiramate can also make hormonal birth control that contains estrogen, such as combined birth control pills, patches, or vaginal rings, less effective, especially at doses above 200 mg a day.

Because of the birth defect risk, Qsymia is available only through a safety program called a REMS (Risk Evaluation and Mitigation Strategy) and only certified pharmacies can dispense it. For people who can get pregnant, the label recommends a pregnancy test before starting and every month after that.

Who should not take topiramate or Qsymia?

The Qsymia label says not to take it if you're pregnant, have glaucoma, or have an overactive thyroid. It also rules out people who take an MAO inhibitor (a type of antidepressant) or stopped one in the past 14 days. Do not use topiramate or Qsymia if you are allergic to phentermine, topiramate, or any of its ingredients.

The label also advises extreme caution with alcohol and other medicines that make you sleepy. It also says to avoid a ketogenic diet or other medicines that raise acid in the blood, since that can raise the risk of kidney stones. Tell your provider if you're pregnant, planning a pregnancy, or have a history of depression.

When to call a healthcare provider

Get medical help right away if you have blurred vision, other sudden vision changes, or pain around your eyes while taking topiramate. Eye problems can lead to permanent vision loss if they aren't treated quickly.

Call your provider right away if you become pregnant, notice mood changes, or have intense back or side pain. Don't stop topiramate suddenly on your own, because the label says it should be stopped gradually.

If you have thoughts of suicide or of harming yourself, call or text 988 to reach the Suicide and Crisis Lifeline, available 24/7. Call 911 or go to the nearest emergency room if you're in danger right now.

Also call 911 for signs of a severe allergic reaction, like swelling of your face, lips, or throat, or trouble breathing.

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