Do not call 911 for a medical emergency involving treatment for pets.
Emergency responders are generally not trained or equipped for veterinary medicine, so they will not be able to help you. However, there are some situations that involve animals that would still be considered a situation for calling emergency services, such as:
- An animal attacking or trying to attack humans
- An animal is being a traffic hazard
- Animal cruelty in progress
What would happen if I called them anyways?
At least in the United States, it would probably be the case that they would simply redirect you to a non-emergency line (in many areas of the United States, this is 311), as long as you didn't do this repeatedly or with obvious malicious intent. Many people mistakenly contact 911 for situations that are not considered true emergencies by emergency services, and as long as the intent isn't malicious, it's generally considered to be more harmful to punish people who call 911 because they didn't know what else to do than to spend the time handling these calls. Emergency responders do not want people to possibly not call 911 in a real emergency because they are afraid they might be misjudging the situation and will end up getting punished for it.
But of course, emergency lines are handled regionally, so this is not necessarily a guarantee in your area, nor should you call counting on them to help you contact the correct services when you know your situation is almost certainly not the type of emergency handled by 911 services. As part of basic emergency preparation, you should familiarize yourself on the policies in your area, and try your best to only ever call any service for those situations it's meant for.
So what should you do if your pet has a medical emergency?
The simple answer is, call your vet.
You should prepare for the possibility of your pet having a sudden medical emergency by having the contact info of a 24-hour veterinary clinic, and any other local pet emergency services, such as the ASPCA's poisoning hotline, prepared before an emergency happens. Keep this information in your phone contacts if you have one, or keep it written down in a place you know you can find immediately even under stress. The common location is posted on the refrigerator door.