The tricky part is the delay. A dog that ate onion today may look normal for several days before signs of anemia appear. Use the onions and garlic calculator for a weight-based estimate, and call your veterinarian or an animal poison control center.
Enter weight and amount to get an urgency level and next steps.
What to do right now
- Move your dog away from the source and pick up anything left over.
- Find the packaging, label, or plant so you know exactly what was eaten and how much.
- Note your dog's weight and the time it happened.
- Call your veterinarian or an animal poison control center. Do this even if your pet seems normal.
- Do not make your pet vomit unless a professional tells you to.
- Follow the advice you are given, and bring the packaging to the clinic.
Why onions and garlic are dangerous
Allium plants contain sulfur compounds that cause oxidative damage to red blood cells. Damaged cells form small clumps called Heinz bodies and are removed from the bloodstream faster than the body can replace them. The result is a type of anemia called hemolytic anemia.
Garlic is several times more potent than onion, gram for gram, and garlic or onion powder is more concentrated still. Toxicosis has been reported in dogs that ate more than 0.5% of their body weight in onion, and larger amounts in the range of 15 to 30 g per kg are commonly cited. Small amounts eaten repeatedly over days can also add up.
Symptoms to watch for
- Vomiting, drooling, or diarrhea soon after eating
- Lethargy and weakness
- Pale gums
- Fast breathing or a fast heart rate
- Red or dark brown urine
- Reluctance to exercise
Timeline: when signs appear
Stomach upset can happen within a day. Changes in the red blood cells begin early, but signs of anemia, such as weakness, pale gums, and dark urine, often do not appear for 3 to 5 days. That is why a vet may recommend bloodwork over several days even if your dog looks fine at first.
Go straight to an emergency vet if
- Your dog shows lethargy, pale or yellow (icteric) gums, weakness, rapid breathing, or dark urine, these can indicate hemolytic anemia already in progress
- The amount eaten was concentrated (powder, dehydrated flakes, soup mix, or bouillon) even in a small total weight
- Several days have passed since ingestion and your dog now seems unusually tired or is exercising less than normal
- A poison control consultation or your vet has told you to bring the dog in
What the vet will do
If the ingestion was recent, the vet may induce vomiting and give activated charcoal. Bloodwork, including a red blood cell count and a check for Heinz bodies, helps track whether anemia is developing.
Most dogs with mild exposure only need monitoring. Dogs with significant anemia may need hospital care, oxygen, IV fluids, and in severe cases a blood transfusion.
How to prevent it
- Never feed table scraps cooked with onion or garlic, including gravy, soups, pizza, and stir fry.
- Check baby food and broth labels for onion or garlic powder before giving them to a sick dog.
- Store onions and garlic in closed cabinets or containers.
- Secure kitchen trash and compost.
For a room-by-room list you can print, see the pet poison-proofing checklist.
Enter weight and amount to get an urgency level and next steps.
Frequently asked questions
How much onion is toxic to a dog?
Toxicosis has been reported above about 0.5% of body weight in onion, roughly 5 g per kg. Garlic and powders are more potent. Our calculator adjusts for the form eaten.
Is cooked onion safer than raw?
No. Cooking does not remove the compounds that damage red blood cells.
Why does my vet want bloodwork days later?
Anemia from onion or garlic often takes 3 to 5 days to show. Repeat bloodwork catches it before it becomes severe.
Is a small amount of garlic healthy for dogs?
Garlic is not recommended for dogs. Even small amounts given regularly can damage red blood cells over time.