My dog doesn't want to eat

Hi please I want to know your opinion. My dog is a 7 months old golden retriever . He usually is very playful with a full energy behaviour . I would like to add that he is not that sociale and doesnt' like walks either. But yesterday  suddenly he didnt want to eat his  meals even though he loves eating. Also he looks lethargic with no reason at all, he has being sleeping many hours during the day. Three days ago he vomited after we went to the vet. Because he tends to be anxius when he goes outside, thats the only thing I can recall as a suspisous thing. Today his lethargic behaviour havent changed much. Do you think he has something I should worried about?   PS: He is a vaccinated dog and he even eats vitamins that her vet recomended. Casually, his state began since he started to eat his vitamins, Do you think it can be secondary effects?  

Hello!  Vomiting and lethargy can be very short-lived; perhaps the pet ingests something that doesn't agree with them, the vomiting reflex empties their stomach and after that they are fine.   However, that doesn't sound like what you are describing; this vomiting / illness is lasting for too long.  A wide range of possible illnesses could present like this, including kidney disease, liver disease, food poisoning, other poisoning, pyometra (females only), pancreatitis, parvo virus, salt imbalance, cancer, foreign body in the stomach / intestine, and so on.   Whatever the cause, whether short lived or long lived, there are usually secondary effects linked to dehydration.  The more vomiting goes on, the worse these become.  Therefore it is important to see your vet, who will assess your dogs' level of hydration and may offer fluids, as well as further investigations to find out what is wrong.  If you wish to wait, then you may be able to call your vets for over the phone triage.  I feel that this is important because this may be an emergency that won't wait.

Regarding the vitamins, you should tell your vet about these.  Some vitamins given with the best of intentions can lead to toxicities; your vet may be able to help you to rule this in or out.

That's a lot of waffling I just did, but the main take home is to contact your vet immediately for triage, so that if this is the emergency that it sounds as though it might be, your dog will be assessed within a suitable time frame.