This is a really popular question I often get! The realistic answer is that there is no finish line to cross because you should always want to meet the physicians in your area. It's similar to asking how many friends you should have - do you ever really stop trying? Of course not. It's the same with medical relationships - you should always want to meet physicians in your community, to know who to refer to, to know who not to refer to and to just be a part of a professional community.
What does vary is the phase of practice you are in. If you are new, you will be actively reaching out to and meeting as many MDs in your community as possible, looking for ones that you align with both in therapeutic approach and in part personality wise. As you become more established you will transition from actively knocking on physician doors, to meeting physicians through activities such as hospital grand rounds and introductions by other physicians and through reputation.
There is no magic number or equation that says if I meet this many MDs I'll get X referrals. There are a lot of variables that come into play. How outgoing are you? Are you more shy and introverted or are you a natural born sales person? What is the climate in your area relative to physician attitudes towards alternative care - the same could be asked about the area you live in and economic pulse all factors that drive how patients seek care and are referred. What's the competitive environment - how many of your competitors are also seekind medical referral relationships? Do you have established networks - maybe a family member or good friend that is in the medical community? How likely is it that the first physician you meet will refer you 100's of patients?
With so many variables the only accurate answer is there is no number - you should always want to meet and mingle with the physicians in your community - and degrees don't matter - you never know what specialist is an influencer in the medical community or can escalate you into the hospital system if that is your end goal.
If you think in terms of numbers the intent is lost - is your intent numbers based for what MDs can do for you or is it relationship based upon which referrals are a benefit? Which one do you think is better for a stable source of new patients that spans the life of your practice?