Can I Give My Dog Aspirin? The Dosage Chart, the Risks, and What Vets Use Instead

It's 11 PM, your dog is limping, the clinic is closed, and there's a bottle of aspirin in the bathroom cabinet. The question that follows is one of the most-searched in pet medicine: how much can I give? The number is easy enough to find — a dozen websites will hand you a milligrams-per-pound rule in one line.

That number is also, genuinely, the least useful thing on this page. For the record, the Merck Veterinary Manual puts the canine range at 10–40 mg/kg by mouth, every 8 to 12 hours.¹ But the veterinary evidence on what aspirin does to a dog's stomach at those doses is the part almost nobody puts in front of owners, and it changes the decision entirely.

How much aspirin can I give my dog?

The Merck Veterinary Manual gives recommended dosages in dogs of 10–40 mg/kg, orally, every 8 to 12 hours.¹ That is the published figure, and it should only ever be applied under veterinary direction. Look closely at it, though, because the width of that range is the story: the top of it is four times the bottom.

Here's what that spread looks like in tablets. Low-dose or "baby" aspirin is 81 mg per tablet, and regular-strength adult aspirin is 325 mg, per the FDA labels on file at DailyMed.⁷

For a 40-pound dog, the published range runs from about two low-dose tablets to more than two adult tablets. Any competent drug label narrows a range like that using weight bands, indications, and safety studies. Aspirin has no such label for dogs — which is exactly why the next section matters.

Formulation and timing matter too. VCA advises giving aspirin by mouth "preferably an enteric-coated tablet," and to "give with food," with a note to contact your veterinarian if your pet becomes ill or vomits.⁴ Both instructions exist for the same reason: to put something between the drug and the stomach lining. Keep reading, though, because the evidence below suggests that buffer does less than owners assume.

Splitting tablets to hit a weight-based number is its own hazard. Enteric coatings are designed to survive the stomach and dissolve further down; cutting one destroys that protection. If a dose can't be reached with whole tablets, that's a conversation with your vet, not a kitchen-scissors problem.

Why isn't aspirin FDA-approved for dogs?

Because nobody ever ran the studies. Merck is direct about the consequence: "Because aspirin is not approved for veterinary use, definitive efficacy studies have not been performed to establish effective dosages."¹ The dose ranges that circulate are inherited clinical convention, not validated figures.

VCA describes aspirin's use in cats and dogs as off-label, or extra-label — meaning "the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada."⁴ Off-label use is legitimate and routine in veterinary medicine when a vet directs it. It's a different thing entirely when an owner does it from a search result.

The FDA also warns that a human NSAID may simply behave differently in a dog: it "may last longer," "be processed differently in the body," "be absorbed faster by the stomach and intestines," and "reach higher blood levels."² None of that is visible from the outside. It's the same reasoning behind the human-medicine cautions in our guide on how much Benadryl you can give a dog.

What does aspirin actually do to a dog's stomach?

It erodes it — reliably, and at ordinary doses. In 1999 researchers at Virginia-Maryland Regional College of Veterinary Medicine ran 24 healthy dogs through 28 days of treatment, looking directly at the stomach lining with a camera (gastroduodenal endoscopy) on days 0, 5, 14, and 28. "Erosions and submucosal hemorrhages were seen in all dogs receiving aspirin. Only minor gastric lesions were observed in the carprofen, etodolac, and control groups."³ Erosions are shallow wounds in the lining; submucosal hemorrhages are patches of bleeding underneath it.

The aspirin group got an average of 16.5 mg/kg of buffered aspirin twice daily — comfortably inside the published range, in a formulation designed to be easier on the stomach. Four regions of the stomach and one of the proximal duodenum were each scored from 1 to 11 and summed, so a dog's total could run from 5 to 55.³ The placebo group sat at 5.0 at every single check.

Now the line that should change how you think about this drug: "No adverse clinical signs were noted in any dog given any treatment."³ Every aspirin dog had a damaged stomach lining. Not one of them acted unwell. Without a camera, no owner and no vet would have known.

Merck corroborates the threshold independently: "Even at therapeutic dosages of 25 mg/kg, plain aspirin may induce mucosal erosion and ulceration in dogs."¹ Read that against the dose table above and the problem is obvious — 25 mg/kg sits squarely inside the recommended 10–40 mg/kg range. The therapeutic dose and the ulcer-causing dose overlap.

Two details make the finding harder to dismiss rather than easier. The comparison drugs were given at their own normal doses — carprofen at about 2.2 mg/kg twice daily, etodolac at about 12.8 mg/kg once daily — so this wasn't a rigged fight between a full dose and a token one.³ And every dog in the study was healthy at the start. Real patients on pain relief are frequently older, often on other medications, and sometimes already carrying kidney or liver disease — the population VCA flags as higher-risk.⁵

⚠️ What does aspirin poisoning look like in a dog?

It starts slowly and lasts a long time. VCA reports that signs "can start within four to six hours and may last 24 hours or longer."⁵ That delay is the trap: a dog who seems fine two hours after getting into the bottle is not in the clear.

The most common effect is stomach upset, "which may include blood, decreased appetite, and elevated body temperature," and "high doses of aspirin may damage major organs like the liver, kidneys, and central nervous system."⁵ At the severe end, Merck describes salicylate poisoning as producing acid-base abnormalities, hemorrhage, seizures, coma, and death.¹

Some dogs start from a worse position. VCA notes that pre-existing clotting disorders, kidney disease, or liver disease raise the risk, and that "dogs already taking steroids or NSAIDs other than aspirin have a higher risk of poisoning."⁵ If your dog is already on a prescription anti-inflammatory, adding aspirin is not a small decision — it's the specific combination the FDA warns against.

If you think your dog has had too much, don't wait to see what happens. Call your veterinarian, an emergency animal hospital, or the ASPCA Animal Poison Control Center at 888-426-4435, and have the tablet strength, the number of tablets missing, and the time ready.⁶

Can I give my cat aspirin?

Not without explicit veterinary direction — and cats are a fundamentally different problem from dogs. The reason is an enzyme, not a body weight. Merck explains that "cats, which lack glucuronyl transferase, metabolize salicylates slowly," and puts numbers on it: "the elimination half-life of salicylic acid in cats approaches 40 hours, whereas it is ~7.5 hours in dogs."¹

Where vets do use aspirin in cats, the interval gives the game away. Merck notes it may be used for its antiplatelet effects in thromboembolic disease "at a dosage of 10 mg/kg, PO, every 48 hours, to allow for prolonged metabolism."¹ Every 48 hours — against every 8 to 12 hours in a dog. VCA puts it plainly: "It is important to dose your cat carefully, as cats are very sensitive to aspirin," because "aspirin clears more slowly from a cat's system."⁴

This is the misconception worth dismantling. A cat is not a small dog that needs a smaller tablet. It's an animal missing the machinery to clear the drug at all.

What can I give my dog for pain instead?

An NSAID that was actually approved for dogs, chosen by your vet. The FDA lists six: carprofen, deracoxib, firocoxib, grapiprant, meloxicam, and robenacoxib.² For cats, only two are approved — meloxicam and robenacoxib.² Each one went through the efficacy and safety studies aspirin never had — which is also why their labels are specific in ways aspirin's cannot be, right down to what to do when a dose is doubled by mistake, as our guide to giving a dog two doses of Metacam shows.

One rule cuts across all of them. The FDA is unambiguous: "Giving an animal two NSAIDs at the same time, or an NSAID with a steroid such as prednisone, increases the risk of side effects in the digestive tract and should be avoided."² VCA gives the same instruction from the other direction — avoid other NSAIDs or corticosteroids while your pet is on aspirin.⁴

So tell your vet if you've already given aspirin, even one tablet. It changes which drug they can start and how soon. And if the underlying problem is ongoing joint pain rather than a one-off injury, the real answer is a long-term plan — see our guide on spotting and tracking arthritis in dogs and cats.

How do you give any NSAID safely at home?

By watching for six specific signs and logging every dose. The FDA lists what owners should watch for on any NSAID: vomiting, diarrhea, bloody or black stool, decreased appetite, decreased activity level, and yellowing of the whites of the eyes or the gums.² Any of them means stop and call the clinic.

But the Reimer study is the reason watching alone isn't enough. Those dogs had eroded stomachs and behaved perfectly normally.³ Your eyes are not the safety net on an NSAID. The dosing record is — because it's the only thing that reliably tells you and your vet what actually went in, and when.

Which brings us to the failure mode VCA names outright, in the missed-dose instructions on its own aspirin handout: "Do not give the pet two doses at once."⁴ On a drug that erodes the stomach at normal doses, a duplicate dose is not a rounding error. And in a house where two people share the care, it's rarely carelessness — it's just that the second person had no way to see the first dose had happened. That's the whole mechanism behind how to avoid double dosing your pet's medication.

Three habits close the gap on any NSAID:

1. Keep one shared record. One place every caregiver can see, rather than a phone alarm on one person's device and a memory on another's.
2. Log the dose as you give it. Not later that evening — at the moment the tablet goes down, so nobody else has to guess.
3. Log the side-effect signs on the same timeline. Appetite, stool, energy, and anything from the FDA's list, dated as you notice it.

That third habit turns a vague "he seemed a bit off last week" into a dated record your vet can actually act on.

Veterinary medical disclaimer: SteadyTails is a logging and coordination tool, not a substitute for veterinary care. Nothing here is a dosing instruction. Aspirin is not FDA-approved for dogs or cats, and should only ever be given on the direction of your own veterinarian, who knows your pet's history. If you think your pet has had too much aspirin, contact your veterinarian, an emergency animal hospital, or the ASPCA Animal Poison Control Center (888-426-4435) immediately.