My doc said a level of 34 was too low, but looking at medline, a normal level is 15-60, so I am not deficient at all.
We really don't know what 'normal' serum levels are. Since in general they are determined by each lab by taking the middle 95% of all their tested persons as normal, and the higest and lowest 2,5% to mean abnormal. But obviously more than only 5% sick get it ever tested!
Therefore these discrepancies: My lab stating 42-83 as normal (by which you clearly would be deficient), but medline stating 15-60 only.
Since we are getting less and less nutrients from natural foods, in this random way determined 'normal' becomes lower and lower. We don't even now what 'normal' would have been a 100 years ago before the SAD -, cutting out most organ meats - and no serum testing avialable at that time.
Since 'normal' really doesn't mean nothing more than a statistical construct constantly lowered by deterioriating nutritional status in the general population, some look at clinical experience for more 'optimal' reference ranges. Others for what is found in the science literature. Like for example labtestanalyzer.com, which came up with these ranges:
ug/dL
Low < 19.99
Sub-Optimal 20 - 29.99
Optimal 30 - 80
Supra-optimal 80.01 - 95
High > 95.01
And also my experimental experience confirms, that incredible health benefits can acrue with optimal ranges - like in my case at about 70 ug/dl (double your level). Which also exemplifies that 'optimal' ranges can be entirely individual. Only found out with contining experimenting by each oneself.