My dog swallowed half a 500 mg Tylenol. Do I need to do anything?

That is 250 mg, which is 100 mg/kg — Merck's threshold for clinical signs — in a 5.5 lb dog, and 83 mg/kg in a 6.6 lb dog. Call your vet or the APCC at (888) 426-4435 with the weight, strength, and time. A normal-looking dog now can still show liver damage days later.

Is there any dose of Tylenol that is safe for dogs at home?

Not one you should set yourself. The margin of safety is narrow, and the drug hits the liver and red blood cells at once. Dogs have their own approved pain and anti-inflammatory medications, dosed by weight by a veterinarian. If your dog hurts, call the clinic instead of the medicine cabinet.

He ate a cold medicine capsule. Is acetaminophen the only concern?

No. Multi-symptom cold products pair acetaminophen with antihistamines, decongestants such as pseudoephedrine, dextromethorphan, and sometimes caffeine, and each carries its own risk. Count the missing doses, bring the package to the clinic, and let them work through every active ingredient.

Acetaminophen (Tylenol)

Toxic

Acetaminophen damages the liver and turns hemoglobin into methemoglobin in dogs. Merck reports signs above 100 mg/kg and methemoglobinemia above 200 mg/kg — one 500 mg Tylenol is already 100 mg/kg for an 11 lb dog.

This food guide has not been reviewed by a veterinarian. It summarises general information from sources and should not be used to decide whether a food is suitable for an individual dog or to assess an emergency.

Acetaminophen (Tylenol) · Illustration — Illustration

Check before feeding

Do not offer as a treat

There is no recommended treat portion for this hazardous item. If swallowed, contact a vet with the amount, time and product details. Do not induce vomiting yourself.

Signs and health concerns

This list includes both observable signs and conditions identified through examination or testing. It cannot establish the cause or whether an exposure is safe.

Vomiting
Loss of appetite
Reduced activity and responsiveness
Lethargy
Fast heartbeat
Jaundice
Pale gums or mucous membranes
Blue-tinged tongue or gums
Difficulty breathing
Weakness
Liver failure

More about this food

The classic case is not a dog raiding a bottle. It is an owner giving half a Tylenol because the dog seemed sore or feverish. It is a kind act with a bad outcome, and it is the reason this page exists. The Merck Veterinary Manual states that clinical signs of acute acetaminophen toxicosis in dogs are not observed unless the dose exceeds 100 mg/kg, and that methemoglobinemia has been reported at doses above 200 mg/kg. Translate that into the bottle in your cabinet. One Regular Strength 325 mg tablet is 100 mg/kg for a 7 lb dog. One Extra Strength 500 mg tablet is 100 mg/kg for an 11 lb dog and 167 mg/kg for a 6.6 lb Chihuahua. Infant and children's liquids are concentrated, and a few milliliters can carry more than the label suggests to someone eyeballing it. Two things go wrong at once. Once the dose exceeds what the liver can safely process, a toxic metabolite starts killing liver cells, and at higher doses hemoglobin is converted to methemoglobin, which cannot carry oxygen. VCA notes that dogs can develop liver damage over several days after small doses, while larger doses cause signs within hours. Watch for stomach upset, decreased or absent appetite, depression, an elevated heart rate, and yellowing of the gums, skin, or eyes; at higher doses, weakness, pale or bluish gums, and labored breathing. Muddy brown or gray-blue gums are a methemoglobinemia emergency. Do this now: read the label, write down the product, the strength in mg, how many tablets are missing, the time, and your dog's weight. Then call your veterinarian, an emergency clinic, or the ASPCA Animal Poison Control Center at (888) 426-4435; a consultation fee applies and they will give your vet a case number. Combination products matter — NyQuil, DayQuil, Excedrin, and prescription opioids like Percocet and Vicodin all contain acetaminophen alongside other drugs, so bring the box. Do not induce vomiting at home. Activated charcoal, the antidote N-acetylcysteine (Merck: 140 mg/kg of a 5% solution IV or PO, then 70 mg/kg PO every 6 hours for five to seven more doses), fluids, and oxygen are veterinary decisions. Go even if your dog looks fine; liver injury builds over days.

Frequently asked questions

My dog swallowed half a 500 mg Tylenol. Do I need to do anything?: That is 250 mg, which is 100 mg/kg — Merck's threshold for clinical signs — in a 5.5 lb dog, and 83 mg/kg in a 6.6 lb dog. Call your vet or the APCC at (888) 426-4435 with the weight, strength, and time. A normal-looking dog now can still show liver damage days later.
Is there any dose of Tylenol that is safe for dogs at home?: Not one you should set yourself. The margin of safety is narrow, and the drug hits the liver and red blood cells at once. Dogs have their own approved pain and anti-inflammatory medications, dosed by weight by a veterinarian. If your dog hurts, call the clinic instead of the medicine cabinet.
He ate a cold medicine capsule. Is acetaminophen the only concern?: No. Multi-symptom cold products pair acetaminophen with antihistamines, decongestants such as pseudoephedrine, dextromethorphan, and sometimes caffeine, and each carries its own risk. Count the missing doses, bring the package to the clinic, and let them work through every active ingredient.

This information is general guidance and does not replace veterinary care. If your dog has swallowed something, contact a veterinarian immediately.