Why Is My Dog Not Eating, Lethargic, and Wanting to Lie Down?

A dog not eating and lacking energy may simply lack a sense of security in a new environment; the owner should first keep quiet and let the dog adapt for a while before trying to interact, while watching whether its spirit and appetite improve.

Also, a dog may stop eating when it feels unwell—check for runny nose, vomiting, cough, diarrhea, or fever, and if anything is abnormal take it to a vet to rule out infectious diseases like distemper or parvovirus. Finally, a female in heat may also be off-food and lethargic because some dogs feel discomfort then; the owner can apply a warm compress or prepare a soft pad for rest.