Aspirin for Dogs: A Chart by Weight, and Why Most Charts Run High

The Chart, by Weight

Built on 10 mg/kg every 12 hours, the low end of the veterinary range, and rounded down to the nearest quarter of a baby aspirin so no dog gets more than the target.

Give with a meal. Every 12 hours, not more often. Plain or buffered aspirin only, never enteric-coated. Check with your vet before the first dose and stop at three days unless they tell you otherwise. Aspirin is not FDA-approved for dogs, and no dose has definitive efficacy studies behind it — this chart is the conservative end of what veterinary references list, not a guarantee of safety.

Why the Charts Online Disagree — and Run High

Search “aspirin chart for dogs” and you get a stack of clinic handouts and pharmacy sheets that do not agree with each other. One says a baby aspirin per 10 lb, another per 15 lb, another a whole adult tablet per 40 lb. They look like small differences. Converted into the unit vets actually dose in, milligrams per kilogram, they are not.

The two most-shared rules both land at about 18 mg/kg. That matters because of one study. In a 1999 trial in the Journal of Veterinary Internal Medicine, 24 healthy dogs were given placebo, carprofen, etodolac, or buffered aspirin at an average of 16.5 mg/kg twice daily for 28 days, and had their stomachs scoped repeatedly. Every dog on aspirin developed erosions and bleeding into the stomach lining. Carprofen, etodolac and placebo showed only minor changes. And the line that should stop anyone reaching for the bottle on autopilot: no dog in any group showed an outward sign.

Other studies point the same way. In a 2006 randomized trial, aspirin at 25 mg/kg three times daily produced significantly more stomach damage and more days of vomiting than either placebo or the dog NSAID deracoxib, from day 6 onward. The Merck Veterinary Manual’s toxicology chapter reports erosions in half of dogs within two days at that dose. At the other end, a 2008 study that gave 10 mg/kg twice daily for three days found no visible damage and no ulceration on biopsy. That is the basis for the chart above: the lowest dose in the range, for the shortest time.

One honest wrinkle. Merck also cites an older study in which buffered and enteric-coated aspirin caused “few effects” at the high dose. The 1999 trial used buffered aspirin and still found erosions in every dog, so buffering is not a safety guarantee — and Merck’s own pharmacology chapter says enteric-coated human products “are not recommended in dogs.”

“Low-Dose Aspirin” Means Two Different Things

Much of the confusion is one phrase. On a pharmacy shelf, low-dose aspirin is the 81 mg tablet — low for a 180-lb adult. In veterinary research, low-dose aspirin means roughly 0.5 to 1 mg/kg once a day, a blood-thinning dose vets use to help prevent clots in dogs with certain conditions, not a pain dose at all. Researchers studying it note that even those established low doses inhibit canine platelets inconsistently.

So when a forum says “my vet put my dog on low-dose aspirin”, that dog may be on a tenth of what a pain chart suggests, for a completely different reason. Copying the number without the reason is how dogs end up over- or under-dosed.

Which Aspirin, and How to Give It

1. Plain or buffered, nothing else. The label should list aspirin as the only active ingredient. No caffeine, no acetaminophen (Excedrin-type products), no “PM” sleep aids.
2. Not enteric-coated. The coating that protects your stomach makes absorption unpredictable in a dog’s.
3. Baby aspirin is easier to dose. An 81 mg tablet splits into quarters of about 20 mg, which is how small dogs get an accurate amount.
4. Always with a meal, and every 12 hours rather than more often.
5. Write down every dose, with the time, so nobody else in the house gives a second one.
6. Stop at three days unless your vet has examined the dog and told you to continue.
7. Canine aspirin chews are still aspirin. The flavoured products sold for dogs are not FDA-approved — the FDA states that no over-the-counter NSAID is approved for dogs or cats — and the same dose limits apply.

Dogs That Should Not Get Aspirin

• Any dog already on an NSAID — carprofen (Rimadyl, Novox, Vetprofen), meloxicam (Metacam), deracoxib (Deramaxx), firocoxib (Previcox), grapiprant (Galliprant). Our guide to carprofen side effects explains why stacking them is the combination vets fear most.
• Any dog on a steroid such as prednisone.
• Dogs with kidney or liver disease, a history of stomach ulcers, or a bleeding disorder.
• Dogs due for surgery or dental work. Aspirin binds platelets permanently, and Merck notes its effect on clotting lasts far longer than its effect on pain. Tell the clinic about any aspirin in the past week.
• Puppies, and pregnant or nursing dogs.
• Dogs under 5 lb, where a quarter tablet is already too much to divide accurately.
• Cats, ever, without a vet. Cats clear aspirin over about 37 to 40 hours against roughly 7.5 in dogs.

Side Effects, and When to Stop and Call

Stomach damage from aspirin is often silent at first, which is why the 1999 dogs looked fine. The signs that it has gone further:

• Vomiting, especially anything that looks like coffee grounds or has blood in it
• Black, tarry stool — digested blood from higher up the gut
• Going off food or sudden lethargy
• Pale gums, or bleeding that will not stop from a small cut
• Drinking and urinating much more than usual
• Panting, weakness, wobbliness or seizures — signs of overdose and an emergency

Stop the aspirin and call your vet the same day if you see any of these. The acute poisoning dose Merck gives is around 450 mg/kg — roughly 50 baby aspirins or 12 adult tablets for a 20-lb dog — but repeated doses cause harm far below that, and Merck reports toxicosis at 100 to 300 mg/kg a day over one to four weeks. If your dog ate a bottle, your vet may make them vomit and give activated charcoal; do not do that at home unless told to.

What Vets Use Instead

Aspirin is not FDA-approved for dogs. These are, all by prescription: carprofen, deracoxib, firocoxib, grapiprant, meloxicam and robenacoxib. They were developed and tested in dogs, they have labeled doses, and in the 1999 trial carprofen at a standard dose caused no more stomach change than placebo. That is the honest reason most vets moved away from aspirin.

For pain that is nerve-related or not fully controlled by an NSAID, vets add gabapentin; for arthritis there is now the monthly injection Librela. And the human painkillers that are never safe — ibuprofen, naproxen and acetaminophen — are covered tablet by tablet in what you can and cannot give a dog for pain.

Where Hemp Fits — and Where It Doesn't

Hemp is not a substitute for aspirin on the day your dog is sore, and it is not an emergency painkiller. There is also no published study of CBD and aspirin given together in dogs, so if your vet has your dog on aspirin, tell them before adding anything.

Where hemp does have evidence is the reason many owners reach for aspirin in the first place: ongoing joint discomfort in older dogs. Five published osteoarthritis studies have looked at hemp extract in dogs, four with positive results, one of them ours. In our own 90-day university trial of 37 dogs, 30 of the 32 that finished showed a benefit; it was open-label with no placebo group, and we say so. For a stiff senior dog, the plan that holds up is a vet-chosen dog NSAID or Librela where needed, weight control, steady exercise and, if you want it, a daily hemp oil alongside — not aspirin from the cupboard indefinitely. See the signs and stages of arthritis in dogs and our guide to hemp and your dog's medications.

Questions Worth Asking Your Vet

• Is aspirin the right drug here, or would a dog-approved NSAID be safer for this problem?
• What exact dose for my dog's weight, how often, and for how many days?
• Does anything my dog already takes — including supplements — rule aspirin out?
• If my dog needs a prescription anti-inflammatory after this, how long should the gap be?
• Which signs mean I should stop it and call you rather than wait for the next appointment?

Frequently Asked Questions

How much aspirin can I give my dog chart?
A conservative chart works from 10 mg per kilogram (about 4.5 mg per pound) every 12 hours, the bottom of the 10 to 40 mg/kg range in the Merck Veterinary Manual, rounded down to the nearest quarter tablet. That is roughly a quarter of an 81 mg baby aspirin for a 5-lb dog, half for 10 lb, one for 20 lb, two for 40 lb and just over four for 80 lb. Confirm the amount with your vet first, give it with food, and do not continue beyond three days without a recheck.

What pain relievers can dogs take?
The ones made for dogs. The FDA lists carprofen, deracoxib, firocoxib, grapiprant, meloxicam and robenacoxib as approved NSAIDs for dogs, all by prescription, and states that no over-the-counter NSAID is FDA-approved for dogs or cats. Vets also use gabapentin and, for arthritis, the monthly injection Librela. Aspirin is sometimes used short-term on a vet's advice. Ibuprofen, naproxen and acetaminophen (Tylenol) should never be given.

What kind of aspirin is OK for dogs?
Plain or buffered aspirin with no other ingredients. Avoid enteric-coated aspirin, which the Merck Veterinary Manual says is not recommended in dogs because absorption is unpredictable, and avoid any combination product such as aspirin with caffeine or acetaminophen. Buffering does not make aspirin safe: in a 1999 trial, buffered aspirin at about 16.5 mg/kg twice daily caused stomach erosions in every dog given it.

Is 81 mg aspirin OK for dogs?
An 81 mg baby aspirin is about 10 mg/kg for a 20-lb dog, which is the low end of the veterinary range, so for a dog of roughly 20 lb or more it can be a reasonable single dose if your vet agrees. For a 10-lb dog it is double that, and for a 5-lb dog four times. Baby aspirin is the easiest form to split accurately, which is why vets who use aspirin tend to work in quarters of an 81 mg tablet.

How long can a dog take aspirin?
Short courses only. In a study of 10 mg/kg twice daily for three days, no ulceration was seen, but at around 16.5 mg/kg twice daily every dog had stomach erosions by day five, without any outward sign. Most vets who use aspirin limit it to a few days. For pain that lasts longer than that, a dog-approved NSAID is both safer and better studied.

Can I give my dog aspirin with carprofen or Rimadyl?
No. Never combine aspirin with another NSAID such as carprofen, meloxicam, deracoxib or firocoxib, or with a steroid such as prednisone. Stacking them sharply raises the risk of stomach ulcers and bleeding. If your dog has had aspirin and your vet wants to switch to a prescription NSAID, tell them when the last dose was so they can decide on a gap between the two.

Can I give my dog aspirin for a limp?
Not as a first step. A limp is a symptom, and the cause decides the answer: a sprain, a torn ligament, a cut pad, a nail and an arthritic flare all look the same from across the room. A dog that is limping but otherwise bright can rest for 24 to 48 hours while you check the paw; a dog that will not bear weight, has a swollen joint, or is still limping after two days needs a vet before any painkiller.

Can cats have aspirin?
Not without a vet. Cats clear aspirin extremely slowly, with a half-life of about 37 to 40 hours against roughly 7.5 hours in dogs, so a dose that is reasonable for a dog builds up to a toxic level in a cat. Vets do occasionally use tiny, widely spaced doses in cats to prevent blood clots, but that is a prescription decision, never a home one.

What if my dog ate a bottle of aspirin?
Call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435 now, with the tablet strength, the number missing and your dog's weight. The Merck Veterinary Manual puts acute aspirin poisoning at around 450 mg/kg, which is about 50 baby aspirins or 12 adult tablets for a 20-lb dog, but stomach damage starts far below that. Do not make your dog vomit unless the vet or poison line tells you to.

All Hemp Oil for Dogs See Our Clinical Trial

What Can I Give My Dog for Pain? · Carprofen · Gabapentin · Benadryl for Dogs · Hemp & Dog Medications

How We Sourced This Article

• Reimer ME, Johnston SA, Leib MS, et al. The gastroduodenal effects of buffered aspirin, carprofen, and etodolac in healthy dogs. J Vet Intern Med. 1999;13(5):472–477. PubMed. Source for the 16.5 mg/kg buffered aspirin finding, the endoscopy scores and the absence of clinical signs.
• Sennello KA, Leib MS. Effects of deracoxib or buffered aspirin on the gastric mucosa of healthy dogs. J Vet Intern Med. 2006;20(6):1291–1296. PubMed. Source for aspirin at 25 mg/kg three times daily vs deracoxib and placebo.
• Wooten JG, Blikslager AT, Ryan KA, et al. Cyclooxygenase expression and prostanoid production in pyloric and duodenal mucosae in dogs after administration of NSAIDs. Am J Vet Res. 2008;69(4):457–464. PubMed. Source for 10 mg/kg twice daily for three days without visible injury.
• McLewee N, Archer T, Wills R, Mackin A, Thomason J. Effects of aspirin dose escalation on platelet function and urinary thromboxane and prostacyclin levels in normal dogs. J Vet Pharmacol Ther. 2018;41(1):60–67. PubMed. Source for veterinary “low-dose” aspirin as an antiplatelet dose.
• Edwards SH. Nonsteroidal Anti-inflammatory Drugs in Animals. Merck Veterinary Manual. Link. Source for the 10–40 mg/kg range, enteric-coated products, platelet effects and feline half-life.
• Hovda T. Toxicoses From Human Analgesics in Animals. Merck Veterinary Manual. Link. Source for erosion, ulcer and toxic doses and emergency treatment.
• U.S. Food and Drug Administration. Get the Facts about Pain Relievers for Pets. Link. Source for the approved NSAID list and the statement on over-the-counter NSAIDs.
• Kogan L, Hellyer P, Downing R. The Use of Cannabidiol-Rich Hemp Oil Extract to Treat Canine Osteoarthritis-Related Pain: A Pilot Study. J Am Holist Vet Med Assoc. 2020;58:35–45. Our disclosure: HempMy Pet supplied the hemp extract and reimbursed clinic costs; we had no involvement in any other study cited here.

If you find something here that conflicts with your veterinarian, email us at support@hempmypet.com and we will correct it.

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. This article is general information, not veterinary advice. Aspirin is not FDA-approved for dogs. Never start, stop or change your dog's medication without your veterinarian.