Can Dogs Eat Onions?
No, dogs can’t eat onions. Onions are toxic to dogs as they can damage their red blood cells. That’s why you must be careful when sharing your food with your dog, as even a small amount of onion can be dangerous. The amount of onion your dog eats matters, so if you’re cooking with onions, please be careful what you share with your dog.
I think my husband and I eat a bag of onions per week, maybe even more. There’s not a single meat-based dish where we don’t add onions! So, I am well aware of how sharing my cooked meals with my dog can be dangerous and tricky, as onions are really not safe for dogs and are classified as toxic. In this article, we’re going to look into a real case of onion poisoning in dogs, see what scientists and vets have to say, and help you stay calm if you think your dog ate some onions.
Understanding why onions are dangerous for dogs
Onions, along with garlic, leeks, and shallots (all part of the Allium family), contain certain compounds that are perfectly fine for us but harmful to dogs. These compounds—sulfoxides and sulfides—can damage your dog’s red blood cells. This can cause a condition called Heinz body anemia. This happens when the red blood cells are weakened and destroyed, which reduces their ability to carry oxygen around the body.
Here’s where it gets tricky: all forms of onions are a problem. It doesn’t matter if they’re raw, cooked, powdered, or even hidden in your leftovers like pizza or stir-fry. Even onion from your burger or onion rings that your dog may steal are all problematic!
Will a small amount of onion hurt my dog?
Just a small amount of onion—about 0.5% of your dog’s body weight—can cause health issues, especially if it’s eaten all at once or over a few days. While cats are even more sensitive to onions, dogs are still highly vulnerable, so it’s important to be very careful when you share your food that has onions! This includes a lot of stuff that we make for holidays (I wrote a Thanksgiving guide for dogs) and a lot of your meal prep meals, like casseroles, pasta, stews, or stir-fries!
| Size of Dog | Amount of Onions (grams) | Amount of Onions (approx. size) |
|---|---|---|
| Toy (5 kg) | 75 | 1/4 of a small onion |
| Small (10 kg) | 150 | 1/2 of a small onion |
| Medium (20 kg) | 300 | 1 medium onion |
| Large (30 kg) | 450 | 1 1/2 medium onions |
| Giant (50 kg) | 750 | 2 1/2 medium onions |
These numbers highlight how even a small amount of onion can quickly become dangerous for your dog, so it’s important to be extra careful about what they eat!
Why are onions toxic to dogs?
What makes onions toxic is a chemical called n-propyl disulfide, which messes with your dog’s red blood cells by reducing their ability to regenerate an antioxidant called glutathione. Without this antioxidant, the cells become weak and start to break apart. This process also creates something called Heinz bodies, which are clumps of damaged hemoglobin. Eventually, this leads to anemia, and symptoms might include pale gums, dark urine, weakness, and even difficulty breathing.
Symptoms of onion toxicity in dogs
If your dog eats onions, the first signs might just be an upset stomach—vomiting, diarrhea, or loss of appetite. However, a few days later, you could notice more serious symptoms as the red blood cells are destroyed. While treatment can help, like IV fluids, blood transfusions, or even antioxidants, there’s no specific antidote for onion toxicity. That’s why prevention is the best strategy: keep onions and foods containing onions far away from your dog.
If you think your dog ate some onions, call your vet ASAP!
How does onion toxicity in dogs actually look like?
I found an interesting study about an experimental case where scientists were feeding healthy dogs onions. It’s a little bit hard to read (and stressful to me), but here’s what it is about.
This study dives into what really goes on in a dog’s body after they eat onions and spoiler alert—it’s not good. The researchers fed six Pekingese dogs a controlled amount of cooked onions (30 grams per kilogram of body weight) for just two days and then monitored their health over the next 24 days. What they found was pretty alarming and confirms why onions are dangerous for dogs.
When the dogs ate onions, their red blood cells took a serious hit. The number of healthy red blood cells started dropping immediately, and by day 5, it was clear the onions were causing hemolytic anemia. This is when red blood cells break down faster than the body can replace them, leaving your dog weak and without enough oxygen circulating in their body.
The first signs of trouble? Heinz bodies. These are clumps of damaged hemoglobin that showed up in the dogs’ red blood cells right on day 1, with a peak by day 3. As the body struggled to deal with the damage, immature red blood cells (reticulocytes) tried to step in, reaching their highest levels on day 8.
The study also found that onions cause major oxidative stress, which means the toxins overwhelmed the dogs’ natural antioxidants. Key enzymes and protective molecules, like glutathione, were depleted. This led to red blood cell membranes becoming stiff and fragile, making the cells even more prone to breaking apart.
By day 3, the dogs started showing signs of anemia, like higher bilirubin in their blood and urobilinogen in their urine—both signs of red blood cell destruction. All of this confirmed that onions are seriously toxic for dogs, even when fed for a short time.
The takeaway? Even a tiny amount of onion can damage a dog’s body severely. This study shows precisely how onion poisoning works and why keeping your dog away from onions in any form is so important—raw, cooked, or powdered. It’s just not worth the risk!
The most important things to remember about whether dogs can eat onions
Is onion powder more dangerous for dogs than onions?
Onion powder is more dangerous for dogs than fresh onion because it’s a concentrated form of onion that contains much higher levels of toxic compounds (n-propyl disulfide). Even a small amount of onion powder can cause serious health problems in dogs, including damaging red blood cells.
Onion powder is sneaky because you usually can’t see it. Unlike fresh onions, which dogs honestly usually avoid because of the strong smell or taste, onion powder is often hidden in foods that taste great to dogs, like sauces, gravies, or seasoning mixes. That’s why it’s so important to check labels and keep your dog away from anything with onion powder. Even a tiny amount can be dangerous, so it’s better to stay safe and double-check the labels!
Love, life, and fur forever!
FAQs
Can dogs eat meat cooked with onions?
No, meat cooked with onions isn’t safe for dogs. Even if it’s just a little bit of onion, the harmful stuff can soak into the meat while it cooks. It might not seem like much to us, but it doesn’t take a lot of onion to harm a dog, especially if they’re small. For example, about half an onion could make a medium-sized dog sick. If your dog sneaks a small bite of meat cooked with onions, don’t panic—it’s probably not enough to cause a problem—but it’s a good idea to keep them away from it in the future.
Can dogs eat caramelized onions?
No, caramelized onions are just as dangerous as raw or cooked onions, and they might be even more tempting to your dog because they’re sweet. Cooking them this way doesn’t remove the toxic compounds—it just makes them taste better. Even a small amount can cause trouble, especially for smaller dogs. For example, a small dog could be at risk from just a quarter of an onion (about 75 grams). Keep caramelized onions off your dog’s plate entirely!
Can dogs eat French onion soup?
Definitely not. French onion soup is full of onions. Even a tiny sip could be enough to cause problems, especially for smaller breeds. On top of that, soups like this often have other dangerous ingredients like garlic, butter, or too much salt.