Short answer — if your liquid gabapentin was left out on the counter overnight in a normal room temperature house, it's almost certainly fine to keep using. One night unrefrigerated won't ruin it. But there are some details worth knowing, because not all liquid gabapentin is the same, and how long it was out and how warm it got both matter.
Reviewed by Sophie, Veterinary Nurse at Dial A Vet
Why liquid gabapentin needs refrigeration
Most liquid gabapentin prescribed for pets is a compounded formulation — meaning a compounding pharmacy made it from powder or capsules into a liquid form, usually with flavouring to make it easier to dose. These compounded liquids typically don't contain the same preservatives as commercially manufactured medications, which is why they need refrigeration. The cold temperature slows bacterial growth and helps keep the active ingredient stable.
The commercially manufactured liquid gabapentin (brand name Neurontin oral solution) is a different story — it contains preservatives and is generally stable at room temperature. But most pets are on the compounded version because it comes in pet-friendly flavours and concentrations.
Check your label. If it says "keep refrigerated" or "store at 2–8°C," it's almost certainly a compounded product.
Left out overnight — is it still safe to use?
In most cases, yes. Here's the general guidance:
Left out for one night (8–12 hours) at normal room temperature (under 25°C / 77°F) — The medication is very unlikely to have degraded meaningfully. Put it back in the fridge and continue using it as normal. One overnight excursion doesn't suddenly make it ineffective or unsafe.
Left out for 24+ hours at room temperature — Still probably okay for a single occurrence, but the margin of confidence drops. If it's a compounded formulation without preservatives, you're now giving bacteria more time to grow and the active ingredient more time to break down. Use your judgment — if it looks, smells, and pours the same as when you got it, it's likely fine, but contact your vet or the compounding pharmacy if you want confirmation.
Left out in a hot environment (in a car, on a windowsill in summer, near a heater) — This is where you should be more cautious. Heat accelerates degradation significantly. If the liquid got warm to the touch, contact the pharmacy or your vet before continuing to use it. You may need a replacement.
How to tell if it's gone off
Liquid gabapentin that has genuinely degraded will usually show some signs:
- Colour change — If it's noticeably darker, cloudier, or a different colour than when you first received it
- Unusual smell — Compounded liquids usually have a mild flavour scent (tuna, chicken, etc.). A sour, sharp, or "off" smell is a red flag
- Particles or separation — Visible floating bits, clumps, or layers that don't mix back together when you shake it gently
- Changed consistency — Noticeably thicker, thinner, or grittier than before
If none of those are present and it was just one overnight on the counter, you're almost certainly fine.
What about the effectiveness?
This is usually the bigger concern for pet owners — not that it's unsafe, but that it might not work anymore. Gabapentin is a reasonably stable molecule, and a single overnight at room temperature is unlikely to cause clinically significant loss of potency. You won't notice a difference in how well it manages your pet's pain or anxiety.
Where effectiveness can genuinely become an issue is with repeated or prolonged temperature excursions — for example, if the bottle has been sitting out regularly, or if it's been going back and forth between the fridge and a warm kitchen multiple times. Compounded medications generally have a shorter shelf life than commercial products (often 30–90 days refrigerated), so consistent storage matters over the life of the bottle.
Tips for keeping liquid medications properly stored
- Keep the bottle on a dedicated shelf in the fridge, not in the door where temperature fluctuates more
- Set a phone reminder for dosing times — you're less likely to leave it out if you put it away immediately after giving the dose
- If your pet gets gabapentin twice daily, take the bottle out, dose, and put it straight back. Don't leave it on the bench "because you'll need it again tonight"
- Write the dispensing date and expiry date on the bottle in permanent marker so you know when to replace it
- If you travel with your pet, use a small insulated bag with an ice pack for liquid medications
Frequently Asked Questions
How long can liquid gabapentin be left out of the fridge before it goes bad?
There's no exact cutoff because it depends on the formulation, the preservatives used, and the ambient temperature. As a general rule, a single overnight at normal room temperature is unlikely to cause problems. Beyond 24 hours, or in warm conditions, contact your compounding pharmacy or vet for guidance specific to your product. Most compounding pharmacies can tell you the stability data for their particular formulation.
Can I use gabapentin capsules instead so I don't have to worry about refrigeration?
Possibly — gabapentin capsules are stable at room temperature and don't require refrigeration. However, capsules come in fixed doses (100mg, 300mg, 400mg) which may not suit small pets who need precise dosing. Some pet owners open capsules and mix the powder with food, but this should only be done on your vet's advice since the dose needs to be accurate. Talk to your vet about whether capsules are a practical alternative for your pet's size and dose.
Does liquid gabapentin for pets contain xylitol?
Veterinary compounded liquid gabapentin typically does not contain xylitol. However, some human pharmacy formulations do use xylitol as a sweetener, and xylitol is extremely toxic to dogs. If your gabapentin was compounded by a veterinary pharmacy specifically for your pet, it should be xylitol-free — but always check the label or confirm with the dispensing pharmacy, especially if you sourced it from a human pharmacy.
I've been leaving my gabapentin out regularly by accident — should I get a new bottle?
If it's been happening frequently — multiple times over the course of the bottle's life — it's worth getting a replacement. Repeated temperature cycling can accelerate degradation even if a single overnight wouldn't cause problems. It's not expensive to get a new bottle compounded, and it's better than discovering the medication has lost potency because your pet's pain or anxiety returns.
If you're unsure whether your pet's medication is still safe to use, or you've noticed your pet's symptoms returning and suspect the gabapentin may have lost effectiveness, you can book a video consultation with our vet team — no app or account needed. We can help you figure out the next step.
— Sophie, Veterinary Nurse, Dial A Vet
Clinically Approved Standard by Dial A Vet Veterinary Team
Disclaimer: The customer and expert messages presented herein may have been altered with artificial intelligence or modified to enhance readability and safeguard the privacy of individuals. This content is for informational purposes only and is not a substitute for professional veterinary advice, diagnosis, or treatment. If your pet is experiencing a medical emergency, contact your local veterinarian or emergency animal hospital immediately. Talk to a vet now.
