I will tell you why my tongue went blue. I wear a collar and I’m an outside cat. I was climbing a fence. I slipped and my collar snagged on the fence. I struggled to get free and started to panic. My collar was strangling me. I was starved of oxygen and became extremely anxious. I almost lost consciousness when I managed to get free. I jumped down and ran into my house where my owner looked at me and asked, “why is my cat’s tongue blue?”
My tongue was blue because I was deprived of oxygen for a while. This is called hypoxia. The tongue and mucous membranes turn blue. It is also called cyanosis. It is a sign of insufficient oxygen in the blood.
Comment: just for a change I wrote this article from the viewpoint of the cat. There are many reasons why a cat might be receiving insufficient oxygen. Some of them are: inhaling toxic fumes such as smoke, solvents and gasoline, being smothered, drowning or being locked in a small airtight space or a foreign body in the airways. Another reason is that the chest has been injured which interferes with breathing.
In the first paragraph I mentioned a cat becoming snagged in a branch of a tree or on a fence which can strangle a cat. We know about this and cat owners are warned to provide an elastic collar which can stretch and slip over their cat’s head in an emergency or use a breakaway collar. This should prevent strangulation.
Another reason why cats might be starved of oxygen is because they are trapped in a pool. Although cats are good swimmers they will struggle to get out of a pool if the sides are steep and there is nothing to grab. The will gradually drown.
An alternative is carbon monoxide poisoning which causes the membranes to become bright red. You will see this when cats are rescued from house fires or, for example, left in a garage with a car engine running and sometimes although rarely when a cat is trapped in a car trunk.
The treatment obviously includes taking your cat to a veterinarian as an emergency while ensuring that your cat has plenty of fresh air to breathe. If you know how to provide artificial respiration it should be carried out. If you have oxygen in a cylinder with a mask (as firefighters are seen to deliver it) then this should be tried as well. Above all see your veterinarian ASAP.