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Can Guinea Pigs Eat Onions? (Serving Size, Risks & More)

Tim Rhodes
Written by Tim Rhodes Last Updated: September 24, 2021

Can guinea pigs eat onions?

Onions are a healthy choice for most individuals.

However, they are poisonous to most mammals.

Let’s find out whether guinea pigs can eat onions, as these small animals will eat almost anything you give them.

Can Guinea Pigs Eat Onions?

No, guinea pigs cannot eat onions and stay healthy.

Actually, onions can kill a guinea pig.

If you feed guinea pigs onions, it is highly likely that your guinea pig will suffer greatly and die.

First, onions do not have many nutritious benefits to your guinea pig.

Besides, if a guinea pig eats an onion, this small animal will most likely have a discharge from the eyes and nose, and elevated salivation.

Second, onions contain disulfide, a substance that can cause extreme anemia in guinea pigs, which is very dangerous.

Last but not the least, just a tiny amount of onions can poison your guinea pig.

Onion poisoning in guinea pigs can be lethal, so contact a vet immediately.

Therefore, if guinea pigs eat onion, they may die.

So, guinea pigs cannot eat onions – they are poisonous to these small animals.

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Onion Facts

People have been consuming onions for at least 7,000 years.

The earliest proof dates back to 5000 B.C.

Onions are rich in antioxidants and known for the powerful flavor and aroma they lend to processed food.

Onions are rich in antioxidants and vitamin C, so this would be the only benefit of onions for guinea pigs.

However, you want to find a much better vitamin C substitute for your guinea pig.

Apart from causing poisoning and extreme reactions in guinea pigs, another reason why guinea pigs cannot eat this vegetable is its high sugar content.

The high sugar content in food can also trigger digestion problems in guinea pigs.

Every guinea pig will exhibit a bad reaction to increased sugar levels, as their bodies cannot digest it will.

Besides, the main food source for guinea pigs is fiber, present in timothy hay and other types of herbs and guinea pig pellets.

Onions belong to the family Allium and are commonly cultivated around the world.

Leeks, garlic, chives, and more are also included in this family.

While we, humans, eat raw onions, we also bake them, grill, fry, and roast them.

Normally, onions are diced and used as an ingredient in many recipes.

Onions are notorious for their chemical properties that can irritate the skin.

Likewise, they are abundant in phytochemical compounds that may have many health benefits for individuals.

As you can see, although they make us cry because of the sulfuric acid they contain, which produces a heavy fume, onions are wonderful for the welfare of humans.

Quick Facts

  • People have been consuming onions for over 7,000 years
  • The ancient Egyptians enjoyed onions. They claimed that the form of the onion signified eternity and the many layers within. They used to place them on the graves of pharaohs for a successful afterlife
  • Onions were a currency back in the Middle Ages and given away as presents
  • Onions make us cry because they contain sulfuric acid (which also irritates the eyes of a guinea pig too!)
  • In the UK, the world’s highest grown onion was discovered, and it holds a record of an incredible 18 pounds
  • Onions are a natural cure for skin conditions, including insect bites or burns

What Are the Nutrients in Onions?

Eating onions is great for humans but not for guinea pigs.

Let’s see what onions are composed of and whether your guinea pigs could benefit from eating onions if these vegetables wouldn’t contain components that are toxic to guinea pigs.

Onions contain:

  • Carbohydrates = 9.34 g
  • Fat = 0.1 g
  • Sugars = 4.24 g
  • Dietary fiber = 1.7 g
  • Protein = 1.1 g
  • Water = 89.11 g
  • Vitamins=
    • Thiamine = 0.046 mg
    • Riboflavin = 0.027 mg
    • Niacin = 0.116 mg
    • Pantothenic Acid = 0.123 mg
    • Vitamin B6 = 0.12 mg
    • Folate = 19 ug
    • Vitamin C = 7.4 mg
  • Minerals=
    • Calcium = 23 mg
    • Iron = 0.21 mg
    • Magnesium = 10 mg
    • Manganese = 0.129 mg
    • Phosphorus = 29 mg
    • Potassium = 146 mg
    • Zinc = 0.17 mg
    • Fluoride = 1.1 ug

Onions do have certain beneficial substances such as vitamin C and vitamin B complex, but your guinea pigs can get all these from their daily cup of fresh fruits and vegetables.

Feeding fresh leafy greens and other tasty safe veggies will make sure your guinea pig is not deprived of the nutrition it needs.

Should You Feed Onions To Your Guinea Pigs?

No, you should never feed onions to your guinea pig.

Not only that the scent and the taste of onion are too intense for your guinea pig’s delicate stomach, but this vegetable is also poisonous to your pet.

Even if onion poisoning in guinea pigs were not likely to occur, there are many other reasons why you shouldn’t think about giving onions to your guinea pig.

Let’s check them out.

Why Are Onions Toxic to Guinea Pigs?

Feeding your guinea pig with onions can not only damage the guinea pig’s urinary tract but also its organs.

Thus, never give onions to guinea pigs.

Onions are also high in calcium.

You shouldn’t feed your pets with food high in calcium because it produces urinary and kidney stones, which can be very uncomfortable when they urinate, cause infections in the urinary tract and blood in their urine.

Another reason why you wouldn’t want to consider feeding your guinea pigs with onions is the high sugar content in this vegetable that causes diabetes, painful digestion, and loose stool.

Besides, disulfide can cause problems in the guinea pig’s respiratory system.

Onions are so dangerous to guinea pigs that they will kill your guinea pig’s red blood cells, which are the primary oxygen carriers.

If guinea pigs eat onion, they will greatly suffer: they will lose their appetite, weight, become anemic, and tired, and these all are just some of the symptoms your guinea pigs would exhibit.

So, do not feed guinea pigs onions at all, as onions are toxic to guinea pigs.

More about the Negative Effects of Onions on the Health of Your Guinea Pig

The first thing you’ll notice if a guinea pig eats an onion is the discharge from your guinea pig’s eyes and nose.

They can display increased salivation as well.

Guinea pigs usually don’t vomit; the first warning would be this instead.

From here, the guinea pig’s health will quickly start to deteriorate.

Seek urgent health attention if you think the guinea pig has eaten onions even in small quantities.

Urinary problems

A serving of onion contains far more calcium than guinea pigs require.

As a result, consuming onion will cause guinea pigs to experience urinary problems, kidney stones, and the like.

Digestive problems

Guinea pigs have a quite sensitive digestive system.

To remain healthy, guinea pigs must eat balanced food, appropriate for their digestive systems.

Sugar is something that they should not eat and sugar levels in onions are quite high.

As their bodies are not built for it, guinea pigs will quickly take harm from this excessive sugar intake.


Of all of the effects of onions on guinea pigs, this is probably the most harmful.

The disulfides in onions damage their red blood cells, causing respiratory troubles and ultimately anemia, both of which are quite severe.


Untreated, or left too long, onion poisoning in guinea pigs can prove fatal.

Take your guinea pig to the veterinarian to receive the care it needs right away.

Even tiny quantities of onion are toxic for guinea pigs.

An intake of as little as 2.5g/pound is potentially life-threatening.

Many guinea pigs are between 1.5 and 2.5 pounds in weight, which means that just 7.5 grams of onions are lethal for them.

The compounds in onions are toxic to guinea pigs because they destroy red blood cells.

This can cause anything from renal dysfunction to the transmission of reduced oxygen within the body.

Bad Calcium To Phosphorus Ratio

You may also know at this stage that calcium can be hazardous.

The same refers to the consumption of phosphorus as well.

Neither is fine in abundance, but what is most important is the ratio.

37mg of calcium and 47mg of phosphorus are present in onions, which is poor.

It opposes a basic requirement of a guinea pig’s diet to consume more calcium than phosphorus.

Note, relative to the previously described toxicity of onions, this is just a minor risk.

Are Cooked Onions Safe for Guinea Pigs?

Onions cannot be cleansed and made healthy for guinea pigs.

Cooking onions doesn’t make them any safer for guinea pigs.

Processing onions will not take the toxins out.

Besides, guinea pigs cannot eat processed food at all.

Similarly, frozen onions wouldn’t make your pet safer.

Only certain types of fresh fruits and vegetables are good for your guinea pig’s healthy diet.

Vitamin C and other important ingredients can come from those other, more stable sources of food for your pet.

What Are the Alternatives To Onions?

So, now that you know the answer to the question can guinea pigs eat onion (no, they cannot), another question arises: what can guinea pigs eat?

Here is a healthy and safe list of foods that your guinea pig can tuck into.

Unlike onions, these ingredients are actually good for guinea pigs.

  • Beetroot
  • Leafy greens (i.e. kale, spinach, and broccoli)
  • Lettuce – in small doses
  • Asparagus
  • Cucumber
  • Green peppers
  • Pumpkin

If guinea pigs chew on any of these foods, it will help in their wellbeing and your pet will remain healthy and happy.

What Kind Of Onions Can Guinea Pigs Eat?

As you have learned, guinea pigs cannot eat onions.

Not only onions cause digestive troubles to your guinea pigs but onion is toxic and lethal to your pet.

Therefore, any nutritional benefits onions would bring to your pet is just not worth the risk of feeding your pet with this vegetable when there are numerous other nutritious foods your guinea pig can eat.

Can Guinea Pigs Eat Red Onion?

No, guinea pigs can not eat red onions because they are also toxic just like any other type of onion.

Onions literally destroy a guinea pig’s red blood cells, cause anemia and damage its organs.

Onions are so damaging that even a slice can cause great harm to guinea pigs.

Can Guinea Pigs Eat Shallots?

No, guinea pigs cannot eat shallots the way we do.

Shallots also include disulfide and thiosulfate, which are detrimental to guinea pigs’ health and also kill their red blood cells, even if you give them to guinea pigs in small amounts.

Can Guinea Pigs Eat Scallions?

No, guinea pigs cannot eat scallions, also known as green onions.

Like other onions, they are life-threatening to guinea pigs.

But the top layers are not poisonous at all, so if you feel like you should feed your guinea pig with the top layers, you may.

Nonetheless, wash those top layers thoroughly before feeding them to guinea pigs since they might have chemicals and pesticides in them.

Yet, here’s another reminder: onions contain disulfide which can cause extreme anemia in guinea pigs.

So, the question is whether you’d want to risk poisoning your pet when there are other options to provide them with all the nutrition their body requires.

What Are the Benefits of Onions for Guinea Pigs?

Onions do not have any beneficial nutrients for guinea pigs other than vitamin C.

Yet, this is not a good enough reason to feed your guinea pigs with onions, as they may die even when fed the smallest amounts of onions.

Onions contain poisonous disulfides, excess starch, excess calcium, etc.

Onion consumption causes very serious symptoms far worse compared to normal urinary complications that most unbalanced and inappropriate guinea pig’s diet can cause.

What To Do If Your Guinea Pig Eats Onion?

Do you think that your guinea pig has taken a bite of onions?

If your guinea pig ate onion, call a vet immediately for explicit instructions about what to do.

Beware of the first signs: discharge of the eyes and nose, and elevated salivation.

Only a tiny amount of onion can do serious harm to your guinea pig.

Guinea pigs will begin to experience stomach pain and general stomach problems due to discharge and salivation.

Eventually, the guinea pig will become anemic, which is fatal for your guinea pig.

How To Prevent Your Guinea Pig From Eating Onions?

Before letting your guinea pig out, remove any potted plants from reach.

Make sure that the pantry door is closed, and that there are no bags of onions on the floor.

Never leave your guinea pig unattended inside or outside of the home.

Should you wish to let your guinea pig outside, simply make sure the garden is blocked off appropriately.

Prevent your guinea pig’s access to all areas where it could find something that can cause harm.

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Final Thoughts

A healthy guinea pig’s diet consists of fiber present in timothy hay and fresh fruits and vegetables rich in fiber and vitamin C.

Likewise, you may feed your guinea pig with guinea pig pellets, which are often enriched with vitamin C supplements.

However, when feeding your pets with fruits and vegetables, make sure to learn which foods are beneficial for your guinea pigs.

Onions are definitely not something you would want to give to your guinea pig because they are highly toxic for these small animals.

If a guinea pig eats onion, it will greatly suffer, as even the tiniest amount of onion is dangerous for this small animal.

Onion poisoning is a serious condition that can be fatal for guinea pigs, so if you think that your guinea pig has taken a bite of onions, make sure to call a vet immediately.


Tim Rhodes
Tim Rhodes

Hi there! My name is Tim Rhodes and I'm a guinea pig enthusiast through thick and thin. My mission is to teach others useful tips and tricks about these cute creatures. When I'm not writing, I enjoy kickboxing and work as an animal trainer.

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Last update on 2023-05-25 / Affiliate links / Images from Amazon Product Advertising API