If you catch a kidney infection early enough will you still need i.v. antibiotics?

In Kids-No: Recent research in children demonstrates that IV antibiotics are usually not needed.

Kidney infection: Most urinary tract infections can be treated with oral antibiotics. The usual situations where IV antibiotics are necessary are if the infection does not improve with oral antibiotics (often requires more than one course) or if the patient has nausea and vomiting and cannot take oral antibiotics. Otherwise, most people can be treated at home with oral medications.