Q. About 4 days ago our dog became lethargic and hasn't been eating normal. We changed his food 2 weeks ago could this be the reason?
A. Two weeks seems like a delayed reaction from a diet change if there were no other symptoms until now. I recommend getting your dog seen by your vet as soon as possible for an exam and labwork. It may be related to the diet change, but it could also be a bacterial or viral infection, having ingested something he shouldn't have, swallowed something that is causing a blockage, there are a number of possibilities.