Gabapentin does have side effects, and some of them are significant. Most people tolerate the drug reasonably well, but roughly 29% of users experience neuropsychiatric effects like dizziness, drowsiness, or confusion. A smaller number face more serious risks, particularly when combining gabapentin with opioids or other sedating medications. Whether the side effects are “bad” depends on your dose, your age, your other medications, and how long you take it.
The Most Common Side Effects
The side effects most people notice are related to the brain and nervous system. Gabapentin works by reducing nerve signaling in the brain, specifically by blocking the recycling of calcium channels at nerve endings, which decreases the release of chemical messengers. That’s how it controls pain and seizures, but it also explains why it makes many people feel foggy or off-balance.
The most frequently reported effects are dizziness, drowsiness, and fatigue. These show up even in healthy volunteers during clinical trials, which means they’re a direct result of the drug’s action in the brain rather than a sign of an underlying problem. About 4% of people find these effects bothersome enough to stop taking the medication entirely. For most, the dizziness and sleepiness are worst during the first few weeks and improve as the body adjusts, especially if the dose is increased gradually.
Weight Gain Over Time
Weight gain is one of the side effects that surprises people because it’s not immediate. In a study of 44 patients on gabapentin for at least a year, more than half gained weight. Ten patients gained over 10% of their starting body weight, and another 15 gained between 5% and 10%. The weight increase typically started between the second and third month of treatment and leveled off after six to nine months, even when the dose stayed the same. This happened regardless of what other medications patients were taking and also occurred in people on gabapentin alone.
Cognitive Effects and Memory
Confusion and mental cloudiness are well-documented gabapentin side effects, and there’s growing concern about what happens with long-term use. A retrospective study of cognitively normal adults aged 65 and older found that starting gabapentin was linked to measurable declines in thinking and memory over the following two years. A large analysis of Taiwan’s national health database found an association between gabapentin use and increased dementia risk, particularly with longer treatment duration and higher cumulative doses.
These findings don’t prove gabapentin causes dementia, but they add to a pattern. Younger users don’t appear to face the same degree of risk, though confusion and difficulty concentrating can affect anyone taking the drug. If you notice that your thinking feels noticeably slower or your memory has worsened since starting gabapentin, that’s worth raising with whoever prescribed it.
Breathing Problems in High-Risk Groups
The FDA issued a safety warning that gabapentin can cause serious breathing difficulties in certain people. The groups at highest risk include anyone also taking opioid painkillers or benzodiazepines, people with chronic lung conditions like COPD, and older adults. The danger comes from gabapentin’s ability to depress the central nervous system, which, when layered on top of other sedating substances, can slow breathing to dangerous levels.
The numbers on opioid co-use are striking. A population-based study found that taking gabapentin alongside opioids was associated with a 49% increased risk of opioid-related death compared to opioids alone. At moderate and high gabapentin doses, the risk climbed to roughly 60%. At very high doses (2,500 mg or more daily), the risk nearly doubled. Low-dose gabapentin did not show a statistically significant increase, suggesting the danger is dose-dependent. If you take opioids for any reason, this interaction is one of the most important things to know about gabapentin.
Mood Changes and Suicidal Thoughts
All drugs that affect brain signaling carry FDA warnings about suicidal thoughts and behavior, and gabapentin is no exception. A large Swedish study of over 190,000 people prescribed gabapentinoids found that treatment was associated with a 26% increase in suicidal behavior. The risk was highest in younger people: those aged 15 to 24 had a 67% increased risk during treatment periods compared to their own off-treatment periods.
An important detail from that study, though: when the researchers separated gabapentin from pregabalin (a related drug often grouped together), gabapentin alone did not show a statistically significant link to suicidal behavior. Pregabalin drove most of the signal. Still, the FDA warning applies to both drugs, and mood changes, increased anxiety, or new depressive symptoms during gabapentin treatment shouldn’t be dismissed.
Risks for Older Adults
Gabapentin is cleared entirely by the kidneys, and kidney function naturally declines with age. This creates a straightforward problem: if your kidneys can’t clear the drug efficiently, it builds up in your system and side effects intensify. Research on gabapentin toxicity in people with reduced kidney function found that elderly patients with multiple health conditions were disproportionately affected. Many had been prescribed doses that were too high for their actual kidney function.
The practical consequences for older adults are falls (from dizziness and impaired coordination), excessive sedation, and confusion that can be mistaken for worsening dementia. The Swedish study also linked gabapentinoid use to increased rates of head and body injuries, consistent with the coordination problems the drugs cause.
Withdrawal Can Be Rough
Stopping gabapentin abruptly, especially after taking it for weeks or months, can trigger withdrawal symptoms that resemble benzodiazepine withdrawal. Reported symptoms include agitation, anxiety, sweating, nausea, insomnia, abdominal pain, tremors, and rapid heartbeat. In one documented case, an older woman who was tapered off gabapentin over 10 days developed severe abdominal pain, chills, cold sweats, agitation, and dangerously high blood pressure.
The recommended approach for discontinuation, particularly in older adults or those with psychiatric conditions, is a gradual taper, reducing the dose by 10% to 25% every two weeks. This is slower than many people expect, but it significantly reduces the chance of withdrawal symptoms. If you’ve been on gabapentin for more than a few weeks, stopping cold turkey is not a good idea.
Putting the Risks in Perspective
Gabapentin is not uniquely dangerous compared to other medications that act on the nervous system, but it’s also not the mild, risk-free drug it was once considered. For years it was seen as a safer alternative to opioids and benzodiazepines, and prescriptions surged. That reputation has been tempered by accumulating evidence about respiratory risks, cognitive effects, and withdrawal potential.
The side effects that matter most to you depend on your situation. If you’re young and otherwise healthy, drowsiness and weight gain may be your main concerns. If you’re over 65, cognitive effects and fall risk deserve serious attention. If you take opioids or have lung disease, the breathing risks are the priority. And if you’re planning to stop the medication, doing so gradually makes a meaningful difference in how you’ll feel during the transition.