Can Rats Eat Onions? Are They Toxic? Advice From a Vet

Most dishes that we cook for ourselves include onions and garlic as flavoring. You may have wondered if onions can also be used to spice up your pet rat’s diet, too.

But can you feed your rats onions? Are they really toxic – also in their cooked form?

Raw onions are toxic to many pets, including rats. The exact amounts needed to cause serious symptoms aren’t known, but it’s best to cut out onions from your mischief’s diet altogether. While cooked onions aren’t quite as dangerous, we recommend that you avoid them, too.

If you want to find out more about onion toxicity in rats, we’ve compiled all the information for you below.

Can You Feed Onion to Your Pet Rat?

Can Raw Onions Kill Rats?

Onions are often found on the list of foods used to kill wild rats. Rats aren’t the only pets susceptible to onion toxicity – onions are dangerous for cats, dogs, horses, and cattle, too1.

Red and Brown Onions

The toxic compound found in onions is N-propyl disulphide, an alkaloid that is present in both wild and domestic varieties of the plant1.

This alkaloid damages the membrane of red blood cells and makes the hemoglobin in them precipitate1. This, in turn, causes severe anemia (low red blood cell count).

The signs of onion toxicosis include weakness, lethargy, exercise intolerance, labored breathing and fast heart rate, icterus (a yellow tinge to the skin and mucous membranes), and blood in the urine2. These clinical signs tend to occur days after the ingestion of the toxin, when the blood cell loss is already very severe.

How Much Onion Is Toxic To Rats?

For many toxins, the exact amount that will cause death in 50% of the animals that consumed it is known due to research experiments – this value is called the LD50 of a poison. However, no such experiments have been performed for onion toxins in rats.

Therefore, the exact amount needed to cause symptoms is not known. It’s likely that rats would need to consume quite large amounts of raw onions to develop severe anemia. In fact, there are several studies in which the researchers fed rats onion extract to actually offset the effect of other poisons3-5.

This probably means that small amounts of onions aren’t of any concern.

Still, it’s best not to run any risks. Therefore, onions should not be fed to pet rats, in any amount or form.

Do Rats Like Raw Onions?

As raw onions are often cited as foods that can be used to keep wild rats away, it’s only logical that rats don’t particularly like the smell or taste of them. However, certain individuals may still choose to try some onion if it is offered to them.

Rats Eating a Head of Lettuce and Other vegetables

For this reason, you should make sure that onions are not accessible to your rats. While raw onions are more toxic than cooked ones, onion toxicosis in dogs and cats has been described after ingestion of cooked onions, as well2.

All in all, it’s best to refrain from offering your mischief onions in any form.

Can Rats Have Onion Powder?

Onion powder has also been described to cause symptoms in other pets, especially cats2. No exact data is known for rats, but it’s best to assume that onion powder may cause toxicosis, too.

Therefore, you shouldn’t offer your mischief any foods that contain onion powder – careful, as this applies to many processed foods!

What Foods Are Not Safe For Rats?

Onions aren’t the only plant that can cause symptoms in rats. Chocolate and coffee also contain toxic compounds. Some vegetables are known to cause issues in their raw form – these include beans, artichokes, potatoes, and sweet potatoes. All of these are fine when offered cooked, though.

Pet Rat and Carrots

Fruit pips and stones usually contain toxic compounds and should always be removed before feeding your rats fruit.

Other foods will not cause instant problems but may cause health issues when fed frequently. These include sweet, salty, and fatty foods. In general, processed foods – while very tasty for your rats – are best avoided altogether.

To Sum Up

Like most other pets, rats can suffer from severe anemia after ingesting onions. As it’s not quite clear how much onion is safe for rats, it’s best not to offer it to them at all. This includes cooked onions and powdered onions, as well as foods that contain these.

If your rat has ingested onions, please contact your veterinarian for guidance on how to proceed and which symptoms to watch out for.


1. Colorado State University. Guide to Poisonous Plants: Onions, wild onions, domestic onions. 2022.

2. MSD Vet Manual. Allium spp toxicosis in animals. 2021.

3. Ige SF, Akhigbe RE. Common onion (Allium cepa) extract reverses cadmium-induced organ toxicity and dyslipidaemia via redox alteration in rats. Pathophysiology 2013;20:269-274.

4. Nassan MA, Soliman MM, Aldhahrani A, et al. Ameliorative impacts of Allium cepa Linnaeus aqueous extract against testicular damage induced by dexamethasone. Andrologia 2021;53:e13955.

5. Roldán-Marín E, Krath BN, Poulsen M, et al. Effects of an onion by-product on bioactivity and safety markers in healthy rats. Br J Nutr 2009;102:1574-1582.