Raising your GPA will come as you add more credits with better grades, but if you already have over 100 credits raising your GPA will take a lot of credits. If you have 30-40 credits it will be easier. It does not matter if you choose to take 20 credits/semester and finish in 2-3 years or if you decide to do 12-15 credits/semester and finish in 4 years. In the end, you will have the same # of credits and therefore the same opportunity to raise your GPA. Now, it will be harder to do well when taking on 20 credits but it can be done. It will be easier to do well when doing 12-15 credits. It really just depends on how long you want to be in school for/how well you feel that you can handle the credit load. Also, vet schools like to see full loads it helps them to see that you can handle the vet school curriculum which is around 18-22 credits/semester (give or take a credit or two). In the end, it does not matter how long it takes to get the requirements done, all that matters is your grade in each class. You unfortunately do not get any benefit to your GPA for doing it in a shorter time frame.