There is a lot left unsaid here, no picture of the animal, no history, feeding pattern weight, vet qualification.
Last time I saw a regular vet diagnosing septicemia for example the snake was actually going in shed so sometime you have to take diagnoses with a grain of salt and usually when vet prescribe highly stressful treatment combined with force feeding it makes me a bit wary.
How/why did you go to the vet in the first place? Symptoms?