What to do if your dog appears sick
Frequently we get calls about health issues with dogs and sometimes I get these calls personally. Now I am not a veterinarian and normally wont give out medical advice because of that and I also feel like people that call our center for questions about medical care are kind of abusing the system because since we do care, we try to help as much as we can but none of the people on staff here and Krabi Animal Welfare are medically trained beyond just the basic stuff.
Unless I know someone personally I will normally just give them the phone number of a trusted clinic in their town but I also know that there are some people out there that are overly nervous any time their dog starts acting a little tired, or throws up their food, or just acts lethargic. Then they look online with some extremely vague search items and see something that scares them in an AI readout that convinces them that their dog or cat is dying right in front of their eyes, which more often than not, is not the case.

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If you are the type of person that gets super nervous and has to take their dog to the vet every time it acts a little less than super energetic then good! you are a wonderful, although perhaps a bit overly worried pet owner.
I found the other day when talking to a friend that the internet when searching for diagnosis for a dog is actually quite similar to searching WebMD for problems with yourself: It almost always paints a very grim picture and this is likely because the website is trying to protect themselves from legal troubles - which in some countries is understandable.
So while I am not giving anyone medical advice, this is what I do and have done for many years when one of my dogs is acting a bit under the weather.
It's not a complicated system.
The other day one of my dogs, shortly after eating, started gagging and making that sound that all dogs make right before they throw up. Then, when she did throw up she took some staggered steps and was really struggling to remain upright. She looked like she was going to fall so of course, I intervened to make her as comfortable as possible. She was acting "funny" and very tired / sick for a while after that. She wouldn't even take any treats or water but here is the first thing that I check.
Is the dog breathing properly?
If the answer to that is "yes" then you are probably not needing to jump in the doggy ambulance just yet. Dogs are very good at keeping themselves alive and will have better "tells" than just throwing up. Again i'm not giving a blueprint for all dogs but I have spent time around thousands of dogs over the past 8 years and I have 3 dogs of my own. If the dog is breathing properly after throwing up... you can probably just chill and let them recover.
wait a few hours and try to give them a treat
If they accept the treat, even if they aren't as excited as they normally would be, this is probably a good indicator that their throat and airways are clear. A dog that is experiencing respiratory tract problems will usually ignore food and will remain in a prone position to keep their airway as clear as possible.

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A dog that is constantly "hacking" probably has something small in their throat and honestly, there isn't anything you can do for them for the most part and attempt on your part to do so could actually make it worse...Also, unless your vet has an endoscopic tool and the ability to quickly anesthetize your dog there is nothing they can either. Dogs will naturally put themselves in a prone position to breathe as well as they can without training. Just let them do this, but of course keep an eye on them.
are they eating later on?
If your dog eats later on, and they should because they did throw up their breakfast, even if they are being a bit fussy about how much they will eat, this is probably a good sign that the dog is doing ok and is just having a bit of a rough tummy because of some grass, or some trash, or well it could be anything... that they ate. Most of the time the dog will "get over it."
If your dog starts to move around and is willing to go for a walk or just go outside for a bit, here is where the real test comes in
is your dog pooping normally?
I'm not going to put a bunch of pictures of dog poop online but if you have had a dog for a while you already know what it normally looks like. The things to look out for is discoloration (especially red) and also consistency. Runny poo can be a sign of wide array of problems but again, most of them are not really worthy of a trip to the vet.
My rule at my house is that i put them under close observation and if they are still acting lethargic and not eating normally after 2 days I will take them to the vet. 99% of the time the times that I have been worried the dogs were right as rain just a few days later. The dog probably doesn't even remember what it was like to be sick.
If the dog's poo is a bit off (like runny) I will wait a day or two then go to the vet.
If the dog's poo is discolored (especially red), we go to the vet right away.
Basically, in the 8 years that I have been dealing with thousands of dogs this system has only ever been wrong once and in that situation the dog was too far gone from a poisoning so a trip to the vet wouldn't have accomplished anything anyway.
All I am trying to say here is to not let the internet get you all freaked out when you type in a few words and it tells you to go to the vet right away! It says that for almost anything and probably for legal reasons so that you can't sue the website if they are wrong, which they probably are most of the time.
At the end of the day dogs (and cats) are extremely good at keeping themselves alive and if you just monitor them (and their poo) for a couple of days you probably don't need to do anything for them other than be there for them and be ready to react should the situation worsen.