All depends on which plan and which primary doctor. My Humana HMO plan doctor is happy to prescribe any medications I want (which is none) plus she wants me to take cholesterol control & blood pressure meds which I really do not need since I exercise regularly and I am strong as a horse at age 78. No pains, no aches, no complains anywhere in my beautiful athletic body hahaha.
In the past before reaching Medicare age, I have had bad HMO’s and good HMO’s...mostly based on who is the primary doc assigned to you. But you can request changes of your primary doc.
My primary doc does not get involved in these things, I have had programs where everything needed to be approved by a primary, but I try not to get in them. They usually end up being restrictive.