How much onion or garlic is toxic to pets?

I belong to an online community of veterinarians that is populated with some of the top experts in various areas of veterinary medicine.  They frequently share their expertise and advice.  I found this topic extremely relevant to our daily practice.

Human health supplements are more popular now than ever.  This has trickled into the pet market, too, especially with foods.  We do have to be careful about assuming that human health supplements are safe and/or effective for pets.  In some cases, they can be outright toxic.  We need to be certain that what we’re giving is ok to give.

The mini-essay below is from a toxicologist who is boarded by both the human and veterinary specialties.  She discusses how and why garlic and onions are on the “No” list in almost every case.


Garlic is more potent than onion; it takes about 5 g of garlic per kg of body weight to cause hemolysis in dogs. Cats are much more sensitive as they have more fragile RBCs. That sounds like a lot of garlic, and it is if you’re talking fresh garlic; but powdered garlic or onion are much more potent and more likely to cause toxicosis than fresh. Onion and garlic powder can be present in a lot of foods, but usually in very small amounts. Exceptions would be things like onion-flavored soup or gravy mixes and some baby foods, which can have considerably higher levels of onion/garlic. Cooked onions/garlic are hazardous because they are more concentrated than fresh and usually are highly flavored with what they were cooked with (e.g. liver and onions), so the animal is motivated to eat more of them. I believe the estimation for cats was less than a teaspoon of cooked liver and onions has caused clinical illness in cats. When inducing Heinz bodies for research studies, generally cats are given onion powder at the level of 1-3% of dry matter intake.

Onions/garlic are metabolized in the GI tract to highly reactive oxidative metabolites. ALL ingested garlic/onion will case some degree of hemolysis in dogs and cats–it’s only when sufficient RBCs have been damaged to alter the overall oxygen carrying capacity of the blood and/or to cause hemoglobinuria that the toxicosis becomes clinically evident.

So, does the small amount of garlic that is generally present in pet foods or yesterday’s beef stew cause RBC injury? Yes, but the level of injury is so low that clinically significant illness would not be expected. Some baby foods contain significant amounts of garlic/onion powder and can cause clinically relevant RBC injury if fed chronically to cats. I definitely do not recommend giving garlic tablets to cats or dogs because IF they have garlic in them, they will induce chronic anemia. That being said, most of the garlic tablets on the market that are labeled as “odor free” have had most/all of the organosulfoxides removed in the ‘deodorizing’ process, so would be less toxic. From a toxicity standpoint, I would say that the currently available flea control products when applied per label to the appropriate species are far safer than using garlic (which doesn’t work anyway) to control fleas or ticks.


Sharon Gwaltney-Brant DVM, PhD
Diplomate, American Board of Veterinary Toxicology
Diplomate, American Board of Toxicology


Filed under Uncategorized

11 responses to “How much onion or garlic is toxic to pets?

  1. Chris

    If there can be RBC injury from even the small amounts of garlic that’s put in pet food, why is it in there at all? That sounds like spitting into the wind to me.

  2. Pingback: Can dogs and cats eat those Mamee noodle snack? - Page 2 -

  3. I have used brewer’s yeast with garlic added to my cat’s food for years and they are great, and it DOES keep the fleas off. No more boric acid in the rugs and on the furniture. No more toxic expensive nicotine poisons. Win-win.

    • I try not to argue with success, and if this routine controls fleas for you, that’s a win. I will respectfully disagree that it’s a win for your cat’s red blood cells, though. Some of them are damaged by the garlic. Perhaps not enough to impact your cat in a visible way, but damage is done, and his/her body has to cope with that.

      I’m very comfortable with the efficacy and safety of the products we recommend for dogs and cats. I’ve personally seen yeast and garlic fail repeatedly to control fleas on pets at our practice, so it’s not a treatment I reach for first.

  4. Is the amount of onion powder in pedigree dog food cumulative?
    and what sort of problems would be noticed.

    • The amount that might be found in pet food isn’t likely to cause a dog to have signs that we can actually see. Some red blood cells are damaged no matter what. It’s just that dogs and cats have a lot of red blood cells in reserve to replace them. The “toxin” doesn’t stay in the body forever, so we don’t see a cumulative effect.

      Signs of anemia include breathing problems, weakness, fainting, lethargy.

      Hopefully that answered your questions. If not, let me know and I’ll try again. Thanks for commenting on the blog!

  5. Amanda Nolan

    So I just found this out and I gave my dogs some pices of chicken seasoned with a little ms dash original salt free seasoning a few days in a row and I often give some spaghetti with sauce just a little of my plate. both have garlic in them. they’re Chihuahuas are they going to be okay

    • There probably isn’t enough garlic in those foods to cause problems for your dogs. Yes, there is always some damage to red cells, but I doubt you’ll see any illness.

      Steer clear of these foods in the future. :)

      Check the ASPCA web page for more info on toxic foods.

  6. kay

    My cat got on the bench and ate some meat loaf that had onion in it. I am not sure how much she had do you think she will be OK? Also she is nursing three kitten’s would the onion be passed on to the kitten’s through her milk? Thanks for your time. Kind regards Kay

    • It totally depends on how much onion, how much she ate, and what her weight is. It’s probably going to be fine, but watch for any difficulty breathing, lethargy, vomiting, or other ‘sick’ sorts of behavior. If anything changes or she seems ill in any way, contact your local vet and have her examined right away. Dogs and cats have some blood cells in reserve, so if it wasn’t a heavy exposure, you may not even see a problem. Just watch for those signs and have her treated if they occur.

      You can also contact Animal Poison Control via the ASPCA. There’s a charge (about $85), but they will work with you and your vet to resolve the case.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s