What do you do if a guinea pig is not eating much?

What do you do if a guinea pig is not eating much?
If your guinea pig is not eating much wait a few days to see if it is eating more but if it continues eating little amounts I would take it to the vets as it may have something wrong with it.
The vet will tell you to kill it so to save money just kill it at home in the shed like a fat granny hiding from a hot guy