Antifreeze Poisoning in Cats - Certain Death?

To my mind, antifreeze poisoning in cats rates as the most serious common toxicity seen in veterinary practice. Stay tuned as I discuss why this is, what signs and symptoms to look for, how much antifreeze will kill a cat and just how likely they are to survive.

 
 

What is antifreeze and and where is is found?

The main active ingredient in antifreeze is a chemical known as ethylene glycol, and it is this that is poisonous. Don’t confuse this with propylene glycol which is a completely different chemical that is found in many products as well as certain foods and drinks. Propylene glycol can be found in certain antifreeze products but even here it is generally considered safe.

Ethylene glycol is the ingredient you need to be worried about.

Now that confusion is out of the way, where do you find antifreeze? The most common use of antifreeze is in cars, either in radiator fluid, screenwash and some de-icers. Understandably then the most common source of antifreeze poisoning in cats is from garages, driveways and workshops.

Antifreeze is though also sometimes put in the water of ornamental ponds and water features and poisoning has been known to occur from this source even though the product has been diluted with a large amount of water. (link to icatcare page)

Are cats attracted to antifreeze + how is it poisonous?

One big issue with antifreeze is the fact that it does seem to be attractive to cats. It has a sweet taste which makes it appealing to dogs (and children) but, as you may know, cats can’t actually taste “sweet”. None-the-less they still appear to be attracted by the taste of antifreeze. This is a real problem as it doesn’t take much antifreeze to be poisonous to cats as I’ll discuss later.

So what does antifreeze do once a cat drinks it (or even just licks it off their paws)? Well, half is actually eliminated from the body unchanged. The other half however is broken down by the liver to form some really dangerous, toxic compounds. It is these that are the real poisons.

Ultimately, these toxins cause metabolic changes within the body and ultimately completely destroy kidney function.

The symptoms of antifreeze poisoning in cats

Clearly you want to know your cat has been poisoned with antifreeze before this point. The signs and symptoms of antifreeze poisoning in cats can be broken down into 3 stages:

  • Stage 1 starts as early as 30 minutes after consuming the poison and lasts up to about 12 hours post ingestion. It is characterised by nervous signs including incoordination, wobbliness, disorientation and mental depression. You are also likely to get vomiting alongside an increase in thirst and urination.

  • Stage 2 takes place between hours 12 and 24 following poisoning. During this time a cat will seem to be improving. Unfortunately though, hidden irreversible damage will be taking place.

  • Stage 3 is when complete renal failure takes place. Urine stops being produced and the symptoms include lethargy, anorexia, dehydration, vomiting, diarrhea, oral ulcers, salivation, tachypnea, and possibly seizures or coma. The kidneys are also often swollen and painful on examination. As you can imagine this is then fatal

Not all cats will progress in exactly this order and in this timeframe. Even so, it is clear that the poison is both fast acting and rapidly fatal.

How is ethylene glycol poisoning diagnosed?

It can be difficult! Testing kits are available but they are not very accurate with some medications resulting in a false positive result. They are also not sensitive enough to pick up all cases of poisoning in cats and so can incorrectly come back with a negative result. In my experience this means that most practices will not even stock these tests.

A blood test to look at general body and organ health will often be the first test run in any cat showing some of the symptoms of antifreeze poisoning I’ve just discussed. These won’t show specific changes that only antifreeze can cause. Instead the results will show changes due to acute kidney failure. This could be due to several different diseases of which antifreeze poisoning is one.

Urine testing can also be very useful and in some cases confirm the diagnosis of ethylene glycol toxicity. What your vet will be looking for is the presence of certain crystals within the urine. These are only present after about 3 hours of poisoning and once once a certain amount of kidney damage has taken place urine stops being produced so you can see that they won’t always be present. Also, some antifreeze products contain a dye that causes the urine to glow under UV light.

Based on the test results, your vet may wish to do other tests such as abdominal xray or ultrasound before reaching a working diagnosis of antifreeze poisoning in your cat.

How to treat a cat with antifreeze poisoning

Needless to say, treatment must begin as early as possible and it must be aggressive if it has any chance of succeeding. This is not a poisoning where treatment can be carried out at home on a tight budget. If it is to be attempted it must take place in the veterinary clinic and may prove to be pretty expensive.

Your cat may be made to vomit so any poison within the stomach is removed. The issues with this though are:

  • This is only useful up to an hour after poisoning

  • It should not be done if a cat is showing any nervous symptoms

  • Cats are notoriously hard to make vomit.

The next step is to try and prevent the formation of the toxic breakdown chemicals. This can be done with repeated intravenous ethanol injections or administration of the drug Fomepizole if available.

Finally, supportive care is given to try and maintain hydration, support kidney function and control any other symptoms of poisoning a cat is suffering from.

How much antifreeze will kill a cat?

The short answer is not a lot. Simply walking through a small puddle and then licking their fur clean is likely to mean that a cat ingests enough antifreeze to be fatal. This is not just because cats are so small, they are in fact over 3 times more sensitive to ethylene glycol than dogs.

The toxic dose of undiluted antifreeze in cats is 1.4ml per kg body weight

This means a standard 10lb (4.5kg) cat only needs to drink a little over 6ml of antifreeze to develop a fatal poisoning.

A teaspoon of ethylene glycol could kill your cat.

Post-Poisoning Prognosis

It’s not good I’m afraid. Ethylene glycol poisoning has a reports fatality rate of around 91-97%. To be honest, I’m surprised it’s not higher.

If you know your cat has been exposed to antifreeze as soon as it happens and you get them to your vet immediately then the prognosis may actually be quite good. The reality however is that in most cases we only know something is wrong when too much damage has already taken place for a cat to stand any chance of surviving.

Often it may well in fact be kinder to consider euthanasia rather treatment once the diagnosis is confirmed.

Preventing antifreeze poisoning in cats

Clearly with such a terrible, deadly poison, thought and energy should be spent trying to prevent it from ever happening in the first place. It’s not rocket science and the first step is to keep any products containing ethylene glycol safely locked away. You don’t even want to give your cat the chance to lick the outside of a container. Disposing of empty containers to prevent this is also important.

If possible, you could also switch to an antifreeze product containing propylene glycol rather than ethylene glycol. Unfortunately these are not always available and where they are, are often quite a bit more expensive.

Some antifreeze products have a bittering agent added to them to make is less appealing to drink. It is unclear just how effective this actually is though, especially when a cat only needs to consume such a small amount for a fatal poisoning to occur. By all means use these products but don’t let them change how careful you are using and storing them.

Take great care using any antifreeze products. Try and avoid spills and if there are any accidents make sure the mess is cleaned up thoroughly straight away. Also keep your cat away whenever you are handling these chemicals.

Finally, check your car radiator regularly and immediately repair any leaks. You don’t want a puddle of liquid forming under your car, especially when it’s cold and the warmth of the engine may be quite attractive to a cat.


Have you ever had a cat suffer from antifreeze poisoning? Please leave your story in the comments below to help other cat owners understand what it is like.

Also make sure you check out my other articles on common cat poisons so you can do your best to protect your cat from anything that might be toxic to them.

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