Every couple of months I get asked this same question. “Doc, what’s my blood type?” I load my “why you don’t need to know your blood type” speech from my cerebrum and press replay, trying to add a little spontaneous variation for authenticity. “Actually, I’ve never checked it.” “I thought you check everything.” “Nobody checks everything. There are thousands of different available blood tests. Most of them would be completely useless to you.” “Well doc, could you check my blood type?” “I’m...