How long does it take for lyme disease fever to go down with oral antibiotic therapy?

Depends: If you caught the disease early, in stage 1 with the initial fever and rash, fever should resolve within a couple of days of starting the antibiotic. If the disease had progressed further before treatment was initiated, it may take a lot longer to become fever free - even 10-14 days. Make sure you don't skip doses and let your doc know if any new symptoms or you're not feeling better.