Do Onions Kill Rats?

Onions will only kill rats if you trick them into eating raw ones. Rats and mice hate the strong onion smell and they will run away from it. However, onions will not kill rats instantly because it takes time to affect their system.

If rats eat onions in a closed area without water, they will die. Raw onion can kill rats because it drains their cells and limits the amount of oxygen they need for survival. They will also become thirsty with serious stomach pains.

Rats are very smart and sensitive little creatures. Additionally, their sense of smell is very efficient. Therefore, you have to mix an onion with their favourite food if you want them to ingest it in large quantities. Based on the information above, onions are good at repelling rats but not efficient at killing them.

Do onions kill rats?
Do onions kill rats?

How to kill and repel rats with onion

There is no way you will cut a fresh onion into pieces and expect rats to eat them raw just like that. Onions will also irritate the rat’s eyes and the harsh pungent smell will tingle their sensitive nose thus driving them away.

To kill rats, chop a fresh onion into tiny pieces. Mix 2 teaspoons of those pieces with a tablespoon of fried minced meat and let them eat it. Raw onions can cause severe anemia in rats and if they eat the mixture in large quantities, they will die.

If you are planning to repel rats, then fine. You can use onions to deter them from entering your house by chopping some pieces of fresh onions and placing them at their usual paths or the entrance of their hideout.

A good example is when you notice that rats have made a hole through your wall, you can place some fresh onion pieces at that exact point or even throw them in the rat hole. If there is any rat hiding, it will definitely run out. This will also keep them from using that hole to get into the house.

Do rats eat onions?

Rats can eat onions but only after they are well cooked. Onions are not harmful to rats when cooked because the toxic elements found in raw onions become weak when exposed to high temperatures. Cooked onions are tasty to rats and they will enjoy the taste of it served in food.

However, you should know that if onions are not well cooked, they can cause serious stomach upsets for the rats. This can make them very weak and even kill them if they took the poorly cooked onions in large quantities.

It is also good to note that rats cannot vomit and this makes onions effective in killing them if they eat lots of it that is not well cooked. There is no way they will get it out of their system and the negative effects will have time to affect them negatively.

You can also cut some fresh onions and keep them in your wardrobes. The fresh pungent smell from onions will keep rats and mice away.

Onion bait (How to trick rats into eating onions)

Some people take this advantage to kill stubborn rats especially if the infestation has become too much. They will simply mix slightly cooked onions with beef stew and add some baby powder into the stew. This is highly poisonous to the rats and they will die soon after eating this.

It is important to keep any form of liquid that can quench their thirst away so that they do not find an alternative to rejuvenate their system. This is only for those who are trying to get rid of rats.

However, if you are keeping one as a pet, you may need to have your onions well-cooked before you feed your pet. You can also use onions to repel rats without killing them especially if you don’t want those that are kept as pets in an area.

It is also good to note that when making onion baits for rats, you should be careful about your pets feeding on the same. Poorly cooked onions can have serious negative effects on your cats and dogs and this is something you may not really want.

Keep the bait in a safe place away from your pets. It is also advisable to use the bait at night when your pets are asleep and the bait area is well locked with no disturbance or movement in the house. Rats are afraid of human activity and they will not feed on the bait during the day.  

How long does it take for onions to kill rats?

It will take up to 12 hours for onions to kill rats if taken in large quantities. This is because rats can only survive up to 30 minutes without oxygen. Onions are known to cause instant anemic symptoms in rats and this will make them weak and less mobile.

When rats ingest onions in large quantities, they will start to experience kidney failure. This will make the rats thirsty in the process.

If they do not find water to drink, they will die. This explains why you may find a dead rat in the open because it was trying to look for water. You can also starve the rats so that they become desperate. This will make them eat anything including poorly cooked onions.

The fact that all this will take time to affect the rat’s system explains why it may take 1 or 2 days for onions to kill rats because it also depends on the amount that the rat has taken. If the rat only eats a very small piece of it, it may not kill it because it may recover from the effects.

Can you use onions to keep rats out of your garden?

You can also use onions to repel and kill rats outdoors as long as they are fresh. You may need to keep an eye on them and have them changed as frequently as possible. This is probably why many people will avoid using them outdoors unless you are very sure of where to place them.

It is also obvious that there is a lot of food alternative out there for rats and onions are the last thing that they would want to feed on. You may only use it to repel them but it is a fact that the ground is probably wide and there may be several other alternative routes.

So the best way to use onions outdoors is to be specific on their tracks and their holes. You may throw fresh onions that are chopped into pieces into their holes and hiding areas. You can also place this on their tracks and this will help in repelling the rats because they hate the smell if not killing them at least for some time.


  • US National Library of Medicine, National Institute of Health: Recovery from dietary iron deficiency anemia in rats by the intake of microencapsulated ferric saccharate
  • Kidney Failure, Poisons by Cinque Ports Vets