As this is a young dog, that likely puts all sorts of things in his mouth and challenges his naïve immune system, we can see vomiting and diarrhea for a number of reasons. The most common reasons for a dog his age to vomit are dietary indiscretion (eating something he shouldn’t have or fatty food if he has a sensitive stomach), ingestion of a foreign body (ie toys, bones, trash, etc.), viral infections (ie parvo, distemper, HGE, etc), toxins, intestinal parasitism (not just the worms, but the protozoa; ie Giardia and Coccidia), and a bacterial gastroenteritis.
The first thing we would want to make sure of it whether he could have gotten into something he shouldn’t have. Toxins (and any chemical) can cause a range of signs, depending on what they have been exposed to, but often will cause drooling due to the material’s taste. If there is any chance that your wee one has gotten into something poisonous, then I would advise being seen by a vet now. But as it has been a few days, it is very possible that something else is the basis of his vomiting.
If you can rule out toxin exposure and foreign bodies causing obstruction in the stomach, then you can try and settle his stomach at home. First, you can try to settle his stomach by resting it by withholding food for few hours.
If you haven’t seen further vomiting by that point, then I would advise giving him a small volume of a light/easily digestible diet. Examples of this would be boiled chicken with rice, scrambled eggs (made with water and not milk), or cottage cheese with rice. There are also veterinary prescription diets that can be used in cases of gastroenteritis, notable Hill’s I/D or Royal Canin’s sensitivity. The easily digestable diet will be better tolerated and absorbed by the compromised gut and should get some nutritents in and result in less diarrhea.
I would offer a small amount and if he keeps that down, a bit more can be offered about thirty minutes later. If no vomiting is seen, then you can increase the volume you are feeding. I usually advise that the diet be continued until the vomiting is settled, and that they are then slowly weaned back to their normal diet over a week.
Now diarrhea and vomiting can quickly dehydrate a young dog, so we need to keep an eye on his hydration. To check his hydration status to make sure they are not becoming dehydrated there are a few things we can test. One is whether the eyes appear sunken, if the gums are tacky instead of wet/moist, and whether the pet has a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a wee video on this HERE. ( They use a big dog but it makes it easier to see). If you are seeing any signs of dehydration alread, since he is so wee, then you do want to have him seen by his vet before this becomes an additional issue for him. If you are concerned that he is become dehydrated, and his vomiting has settled, you can offer or even syringe feed her pedialyte. A typical maintenance rate for hydration in an animal is 48 millilitres per kilogram of body weight per day. This value will give you the total he needs for the day (though doesn’t take into account vomiting losses) and is a good starting point to give you an idea of his daily requirement. If he vomits you given pedialyte, I would discontinue this as a therapy. (since we don’t want him vomiting more because of our intervention).
If you initiate these treatments and do not see improvement over the next 12-24 hours (especially as he is essentially a baby and has little body reserve), then I would advise taking him to the vet so that they can rule out other possible causes of these signs. They will be able to rule out fever, assess his hydration, and have a feel of his gut to make sure there is no obstruction. Ideally, a fresh fecal sample should be brought along so that it can be submitted for analysis (to determine the underlying agent for the diarrhea) but your vet and yourself may wish to trail him on a short course of antibiotics and canine friendly anti-diarrheal medication (ie kaogel).
I hope this information is helpful. Please do let me know if you have any further questions. If you have no further questions, feedback is always appreciated.
All the best,