Your B12 is marginal. Not really low but it would be best to be higher since you have neurological symptoms. 400pg/ml is the new low. The lab range you quote, is outdated ...anything below 400pg/ml should be supplemented.
1000mcg of activated methylcobalamin once a day on an empty stomach is enough for you since you are not below 400. You can take more, but avoid food ...because it won't get absorbed.
The D3 OTC rule is 1000IU of D3 for every 10 pts to raise.
A good goal is 50....so you would need 2000IU a day.
It takes a while to get levels up. Retest in 3 months, and see where you are. (don't take the B12 for about a week before testing to get a good idea of where you are without a supplement).
Some people cannot activate the synthetic Cyanocobalamin used as B12 ....so get the methyl form for best results.
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All truths are easy to understand once they are discovered; the point is to discover them.-- Galileo Galilei
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Weezie looking at petunias 8.25.2017
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