When I was initially diagnosed with PMR at Mayo Rochester, my rheumatologist prescribed 20mg prednisone as my starting dose. My pain level at the time was about 7 to 9 on my scale of 0 to 10. The appointment was in the morning and also had a follow up with him at 3pm the same day. We picked up the prednisone at the pharmacy and I took my first dose at noon with lunch and by 3pm my pain was almost all gone (less than 1). I was still stiff and a little achy but so much better than in the morning. When I started tapering, if my level of pain was greater than a 2, I didn't taper and sometimes depending on the amount of pain, I increased the dose to half of my previous amount that I tapered down.

I understand the doctor wanting to confirm PMR since there are quite a few different conditions that mimic PMR and the quick way doctors diagnose PMR is seeing if you respond to a starting dose of prednisone (in my non medical opinion). Here's some more info on the conditions that mimic PMR - https://www.medicalnewstoday.com/articles/diseases-that-mimic-polymyalgia-rheumatica.