50 nmol/l (20 ng/ml) is right in the middle of the 'insufficient' range. Did you mean ng/ml? The upper limit for most labs is between 175 and 200 nmol/l. In my

50 nmol/l (20 ng/ml) is right in the middle of the 'insufficient' range. Did you mean ng/ml? The upper limit for most labs is between 175 and 200 nmol/l. In my personal example, taking about 6000 UI (plus 300 mcg K2) for a year put me just under 200 nmol/l. I did an experiment and stopped taking it for 2 months (but kept taking K2). After testing again I had dropped to 70 nmol/l (top of the insufficient range) and had mild symptoms of muscle ache and fatigue. Needless to say, I've started taking it again (and will aim for 175 nmol/l).