Gabapentin causes drowsiness, dizziness, and coordination problems more than any other side effects. In clinical trials, roughly 1 in 5 people experienced significant sleepiness, and nearly as many reported dizziness. Most side effects are mild and improve within the first few weeks, but some, like weight gain and cognitive changes, can develop over longer use.
The Most Common Side Effects
Sleepiness and dizziness are the two side effects you’re most likely to notice. In FDA clinical trials for nerve pain, 21% of people taking gabapentin reported drowsiness (compared to 5% on placebo), and 28% reported dizziness (compared to 8% on placebo). In epilepsy trials, the numbers were slightly lower: 19% for drowsiness and 17% for dizziness. These effects tend to be strongest during the first week or two and often ease as your body adjusts.
Coordination problems are also common. About 13% of people in epilepsy trials had trouble with balance and steady movement. This is especially relevant if you’re physically active or work a job that requires precise motor control. Other frequently reported effects include fatigue, nausea, blurred or double vision, headache, and mild swelling in the hands or feet.
Weight Gain
Gabapentin can cause noticeable weight gain in some people. One study found an average gain of about 5.5 pounds after just six weeks of use. Not everyone experiences this, but it’s common enough that it’s worth watching. The weight gain appears to come from increased appetite rather than changes in metabolism. If you notice your appetite shifting significantly after starting gabapentin, that’s a recognized effect of the drug, not something unrelated.
Cognitive Effects and Memory
Many people on gabapentin describe a mental fogginess: difficulty concentrating, slower thinking, or trouble finding words. This is a well-documented short-term effect that overlaps with the drowsiness the drug causes. For most people, it’s mild and manageable.
Longer-term cognitive effects are a growing concern, though. A study published through BMJ found that people who received six or more gabapentin prescriptions were 29% more likely to be diagnosed with dementia and 85% more likely to be diagnosed with mild cognitive impairment within 10 years, compared to people with similar pain conditions who weren’t prescribed the drug. The risks climbed higher with more prescriptions: those with 12 or more were 40% more likely to develop dementia. Adults between 35 and 49 appeared particularly vulnerable, with more than double the dementia risk and more than triple the risk of mild cognitive impairment compared to non-users. This is observational research, meaning it can’t prove gabapentin directly causes these conditions, but the pattern is strong enough to take seriously, especially for younger adults on the drug long-term.
Breathing Problems
The FDA added a warning about serious breathing difficulties in people taking gabapentin. The risk is highest in specific groups: people who also take opioids or benzodiazepines, people with lung conditions like COPD, and older adults. In these populations, gabapentin can slow breathing to dangerous levels.
Symptoms to watch for include unusually shallow or slow breathing, extreme sleepiness you can’t shake, confusion, and bluish discoloration of the lips or fingertips. If you take gabapentin alongside any other sedating medication, this is the most serious risk to be aware of.
Interactions With Alcohol and Other Drugs
Drinking alcohol while on gabapentin amplifies the drowsiness, dizziness, and impaired thinking the drug already causes. The combination can make you far more sedated than either substance would alone. This isn’t a minor interaction. It meaningfully affects your ability to drive, operate equipment, or make clear decisions.
The same compounding effect happens with opioids, benzodiazepines, sleep aids, and certain antihistamines. Any drug that slows your central nervous system will stack with gabapentin’s sedating properties. For older adults taking multiple medications, this combination also raises the risk of falls and fractures.
Risks for Older Adults
People over 65 face amplified versions of nearly every gabapentin side effect. The drowsiness and coordination problems that are merely inconvenient for a 30-year-old become fall risks for an older person. When gabapentin is combined with two or more other central nervous system medications, the risk of falls and resulting fractures increases further. The breathing concerns are also more pronounced in this age group, even without other risk factors like lung disease.
What Happens When You Stop
Gabapentin should not be stopped abruptly. Withdrawal effects are more likely if you’ve been taking it for more than six weeks or are on a high dose. Stopping suddenly can trigger rebound symptoms including increased anxiety, insomnia, nausea, pain, and in some cases seizures, even in people who don’t have epilepsy.
The standard approach is to reduce your dose gradually over at least one week, with changes happening no more frequently than once per week. Some people need even slower reductions, spacing dose changes out every one to two weeks to avoid discomfort. The timeline depends on how long you’ve been on the drug and your current dose. If you’re considering stopping gabapentin, the taper needs to be planned rather than improvised.