Does Gabapentin Cause Weight Gain? Here’s What You Need to Know

Gabapentin (Neurontin) is a medication that’s FDA approved to treat certain types of seizures. It also treats nerve pain from shingles (postherpetic neuralgia, or PHN). It’s used off-label to treat other conditions, such as alcohol use disorder and anxiety. Two long-acting versions of gabapentin — Horizant and Gralise — are also FDA approved to treat PHN. Horizant is approved for restless leg syndrome, as well.

Many people starting gabapentin wonder if it can cause weight gain. While weight gain isn’t a common gabapentin side effect, it’s still possible. Other factors can lead to weight gain while taking gabapentin, though they may have nothing to do with gabapentin itself. 

Does gabapentin cause weight gain?

Some research indicates that 2% to 3% of people taking gabapentin gain weight. Often, this is temporary and due to peripheral edema (fluid buildup in the ankles and feet). Up to 8% of people taking gabapentin can have peripheral edema, and it can occur with or without weight gain.

You can also gain weight while taking gabapentin even if you don’t have peripheral edema.

Why does gabapentin cause weight gain?

If you experience peripheral edema from gabapentin, this means your body is holding onto extra fluid. This water retention can make the number on the scale go up. Peripheral edema from gabapentin is more likely with higher doses (1,800 mg per day or more). But it can happen at any dose.

However, we don’t have a lot of research on how gabapentin causes weight gain without peripheral edema. Some research in animals suggests that gabapentin increases appetite, which can lead to weight gain.

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It’s important to realize that any weight gain may not be from gabapentin itself. Several other factors can also cause weight gain, such as changes to diet or an exercise routine.

How much weight will you gain from gabapentin?

The amount of weight gained can vary from person to person. In the limited studies we have on gabapentin and weight gain, the number of pounds gained ranged from about 2.5 lbs to 5 lbs.

If you do gain weight, available research says it’s likely to occur within the first 3 months of starting gabapentin.

Which factors affect how much weight you’ll gain from gabapentin?

Gabapentin can cause fatigue and tiredness, which can make you less likely to be physically active. This can lead to weight gain over time.

Genetics may also play a role. Research suggests that you can have a genetic predisposition to obesity and weight gain. That may make you more likely to gain weight in several different circumstances, including from gabapentin treatment.

What other medications can cause weight gain?

Besides gabapentin, several other medications can cause weight gain. The table below lists a few examples.

Reasons that medications cause weight gain

As you can imagine, it can be difficult to pin down exactly why you or a loved one may be gaining weight with gabapentin or other medications. Medication-related weight gain can happen for several reasons:

• Increased appetite: Medications like gabapentin, steroids, and some antidepressants can stimulate your appetite. As a result, you might eat more than usual and gain extra pounds.

• Fluid retention: Some medications like pioglitazone and gabapentin can cause your body to hold onto more fluid, which can cause weight gain. Pioglitazone can also cause the body to create more fat.

• Increased fat storage: Some medications can cause weight gain by affecting how much fat your body stores. One example is insulin.

• Slowed metabolism: Some drugs, like beta blockers, can slow down your metabolism. This means your body is not able to burn calories as quickly, which can lead to weight gain.

• Difficulty exercising: Some medications can make it more difficult to exercise by making you tired or fatigued, such as diphenhydramine, gabapentin, and more. As a result, you may burn fewer calories than usual and gain weight.

EXPERT PICKS: WHAT TO READ NEXT

• Medications that cause weight gain: Several medications can cause weight gain. But some are more likely to do so than others.

• Gabapentin side effects: Weight gain is a possible gabapentin side effect, though it’s not the most common. Drowsiness, dizziness, and swelling are more likely.

• Gabapentin FAQs, answered: Knowing how long gabapentin takes to work, and what to expect while taking it, can help you get a better understanding of your treatment.

How to avoid weight gain from gabapentin

First, make sure you’re taking the correct dose of gabapentin. Don’t take more than what’s prescribed. Taking high gabapentin doses can increase your chance of weight gain and other risks like severe drowsiness.

If you do experience weight gain with gabapentin, don’t stop taking your medication without speaking to your prescriber first. They can help provide specific guidance based on your situation and medical history. For some people, stopping gabapentin can have more risks than benefits.

If you recently started taking gabapentin and notice weight gain, ask yourself these three questions:

• Have I changed my diet recently?

• Am I doing less physical activities?

• Have I been feeling more stressed lately?

If you answered “no” to all three of these questions, you may want to consider whether any medications might be the reason for your weight gain. Your prescriber can help you determine this. Keep in mind that if you take any medications besides gabapentin, there’s a chance that they could be to blame.

If you think that certain lifestyle changes have led to weight gain, there are several steps you can take. You can try adjusting your diet and exercise routine to offset the weight gain. Keeping track of your food and exercise habits can also be a helpful way to track lifestyle changes. In doing so, you and your prescriber can better understand whether gabapentin, or something else, has caused weight gain. 

If gabapentin is thought to be the cause, your prescriber may recommend an alternative medication.

Does gabapentin have other side effects?

Weight gain isn’t the most common gabapentin side effect, though peripheral edema is fairly common. Other common side effects of gabapentin include:

• Drowsiness

• Dizziness

• Fatigue

• Trouble with coordination

Gabapentin can have serious side effects, too, but they’re rare. Examples include:

• Withdrawal symptoms if you stop taking it abruptly or your dose is decreased quickly

• Mood or behavior changes in kids

• Suicidal thoughts or behaviors

• Slowed breathing when used with other medications that can affect breathing, such as opioids, benzodiazepines, and alcohol

• Severe allergic reactions, such as Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome

This isn’t an all-inclusive list of side effects. So talk to your prescriber about what to watch out for when starting gabapentin.

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Written by:

Alex Brewer, PharmD, MBA

Alex Brewer, PharmD, MBA, is a licensed pharmacist specializing in chronic disease and health and wellness. Upon completing his residency, he worked in the managed care field, conducting medication therapy management and adherence counseling sessions with Medicaid, Medicare, and private insurance patients, before transitioning to a career in medical writing.

Edited by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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