Do doctors think it's ever normal for blood sugars to be 50 or below in a non-diabetic?

Unusual: Normal people eating food seldom get a glu that low. A glu tolerance test (75 g pure glu when fasting) can provoke this sometimes, but a GTT is not reflective of real food. Another problem is verification. A glucometer is not accurate in that range. A hospital glu can be inaccurate (the blood sits around too long before assay). There are hypoglycemic syndromes, but they are rare. See your md.