My guinea pig is not eating. What do I do?

Your guinea pigs needs to be on Critical Care, which is a powdered formula that is mixed in water and syringe fed, some guinea pigs like it so much they will eat it of a spoon or plate. He should get 12 to 14 cc 4 times a day.I am quite shocked the vet did not suggest this, as you have to buy it from a vet, however, it is not expensive, the last bag I purchased only cost me $11.00. Call other vets in the area that treat guinea pigs and see if they carry the product, I have purchased it several time from vets that I do not treat with simply because they were closer to my home.