Ibuprofen, Paracetamol and Other Human Painkillers
Human painkillers are among the most common dog poisonings, often given by owners trying to help. What each one does, and what to do instead.
Written by thecanineledger
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If your dog has swallowed any human painkiller, including one you gave on purpose, phone your vet, an emergency clinic or an animal poison helpline now. Have the packet with you.
The Merck Veterinary Manual opens its chapter on human painkillers with a sentence that will make some readers wince: “Dogs and cats typically are exposed to human analgesics either inadvertently through accidental ingestion or deliberately by well-meaning but unknowledgeable owners” (Merck, Toxicoses From Human Analgesics in Animals).
Deliberately. Some of these poisonings come from owners who saw their dog limping and reached for the same tablet they would take themselves. The chapter’s summary is blunt about how often: “Ingestion of a human NSAID by small animals is one of the most common poisonings reported to animal poison control centers.”
It is an understandable mistake. While the instinct to ease a dog’s pain is exactly the right one, a human painkiller is the wrong tool for it. Dogs process these drugs differently, the margin between a helpful amount and a harmful one is narrower than in people, and the damage often isn’t visible until days later. Don’t give your dog any painkiller your vet hasn’t prescribed for them.
1. How common this is
Over-the-counter medicines and supplements were the single largest category of calls to ASPCA Poison Control in 2025, at 16.9%, and the ASPCA says “Vitamins, dietary supplements and pain medications still make up most of these exposures” (ASPCA, Top 10 Toxins of 2025). Those are US figures from one service.
Merck adds that “Acute ingestions of human analgesics are reported to animal poison control centers daily,” and that dogs are the species most often involved.
2. Ibuprofen
Ibuprofen is the one most often given with good intentions, and the one Merck is plainest about: “Use of ibuprofen is no longer recommended in dogs, because it may result in gastric ulcers and perforations.”
The damage is mainly to the stomach, the gut and the kidneys. Merck lists “GI irritation or ulceration, GI hemorrhage, and renal damage” as the most commonly reported effects, and adds that “Ibuprofen has a narrow margin of safety in dogs.”
A narrow margin means the gap between an amount that does nothing and an amount that does harm is small. It is not a drug to experiment with.
3. Naproxen
Naproxen lasts much longer in a dog than in a person. Merck notes that “The long half-life of naproxen in dogs (74 hours) appears to be due to its extensive enterohepatic recirculation.” In plain terms, the dog’s body recycles the drug through the liver and gut rather than clearing it, so a single tablet keeps working for days.
Merck’s chapter describes cases of naproxen poisoning in dogs from repeated small amounts as well as single larger ones, with vomiting, black or bloody stools, pale gums and weakness among the signs.
4. Paracetamol (acetaminophen)
Paracetamol is called acetaminophen in North America. It is often thought of as the gentle one, because in people it is easier on the stomach. In dogs, the concern is the liver.
Merck notes that “Icterus, hepatotoxicosis, and necrosis are more common with acetaminophen toxicosis in dogs than in cats,” and that dogs can also develop a sudden dry eye after swallowing it. It also warns that “Toxicosis can occur at lower doses with repeated exposure.” That matters for an owner giving a little every day for a stiff old dog.
Cats are far more sensitive still. If you have a cat, keep paracetamol well away from it too.
Our note: We don’t print Merck’s figures for the amounts at which signs appear. The concern is the liver, and repeated small amounts add up.
5. Aspirin
Aspirin is the oldest of these, and the one owners most often say a vet “used to” recommend. Merck notes that “Dogs tolerate aspirin better than cats do; however, prolonged use in dogs can lead to gastric ulcers.” Signs of poisoning include vomiting, sometimes with blood, weakness, fast breathing and, in severe cases, seizures.
If your vet has prescribed aspirin for your dog for a specific reason, follow their instructions. Don’t start it yourself.
Our note: Some vets may still prescribe aspirin for specific reasons. Give it only if your vet has prescribed it.
6. The hidden ones: cold and flu remedies
Painkillers often turn up in products that aren’t sold as painkillers. Merck warns that “Acetaminophen and some NSAIDs are present in many cough and cold products, making accurate product identification essential to successful treatment.”
So if your dog gets into a cold and flu remedy, a combination tablet or a hot-drink sachet, bring the packaging. The vet needs to know exactly what was in it.
Merck flags one other trap. Some human liquid forms of gabapentin, a drug that is also prescribed for dogs, contain xylitol, which is poisonous to dogs. If your dog has been prescribed gabapentin, use the form your vet supplies or names. → Xylitol: Where It Hides, and Why Minutes Matter
Our note: A dog’s prescription can lead an owner to a human version of the same medicine. Check with your vet before giving your dog any human product.
7. What to do
If your dog has swallowed a human painkiller:
- Phone now, even if your dog seems fine. With these drugs, the damage often comes before the signs.
- Have the packet: the drug, the strength, and how many tablets are missing.
- Don’t make your dog vomit unless the vet tells you to. → My Dog Ate Something: Why You Shouldn’t Make Them Vomit Without a Vet
There is reassurance in the same chapter: “With early detection and proper management, the outcome of analgesic ingestion is generally very good.” Early is the word that matters.
If you gave it on purpose, tell the vet that too, and how much and for how long. Merck notes that owners “often treat their pets with a human NSAID and do not recognize their error until clinical signs occur.” Nobody on the other end of the phone will be surprised, and the information changes the treatment.
Our note: Phone for any human painkiller, including a single tablet.
8. If your dog is in pain
The reason most owners reach for a painkiller is that their dog is hurting. That is worth acting on, properly.
There are anti-inflammatory painkillers made and licensed for dogs, and your vet can prescribe one after examining your dog. They are not risk-free either, which is why they come with a prescription and, for long-term use, monitoring. → NSAIDs in Older Dogs: Benefits, Risks, and the Monitoring Question · → Arthritis Treatment: What Works, From Weight to Medication
Learning to see pain is also worth the time, because dogs hide it well. → Reading Pain in an Old or Sick Dog
Our note: “Anti-inflammatory painkillers made and licensed for dogs” is our general description.
9. What we could not verify
| Commonly said | What we found |
|---|---|
| “A small dose of ibuprofen is fine for a dog” | Contradicted. Merck: ibuprofen “is no longer recommended in dogs” and “has a narrow margin of safety.” |
| “Paracetamol is the safe one” | Not for dogs. Merck: liver damage is more common in dogs than cats with this drug, and repeated small amounts can cause poisoning. |
| “Baby aspirin is safe for dogs” | Not something to start yourself. Merck notes prolonged aspirin use can cause stomach ulcers in dogs. Only on a vet’s prescription. |
| Dosage charts for human painkillers in dogs | Not printed here. We print no doses. |
| “Signs appear straight away, so if my dog is fine, it’s fine” | Wrong. With several of these drugs, Merck describes damage that shows over days. |
Sources
- Merck Veterinary Manual: Toxicoses From Human Analgesics in Animals (Hovda; full review Jul 2024, updated May 2025)
- ASPCA: The Top 10 Toxins of 2025 (charity; US call data; published 15 Mar 2026)
Always confirm with your vet before acting on anything on this page.