Concus,

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Increasing your B vitamins can help strengthen your immune system. Your gray area B-12 is likely meaning at the low end of the healthy range. Many with PCS need to be at the top or above the high end, 1000 pcgms/mL. D3 would be the same. There are two forms of cobalamin, cyano and methyl. Methyl is better. I'm surprised a supplement with nootropics (Bacopa monnieri) would be so low in B vitamins. A good daily dose of anti-oxidants (C and E) can help, too.

Basic immune support diet and reducing stress should help you get back to normal. It is near impossible to find a doctor who is willing to recognize or treat such minor symptoms. They are more likely to throw anti-anxiety or antidepressants at you.

Resolving your sleep issues can be a big help. Napping during the day is not helpful, even if you concussion was recent. Sleep rest is not highly recommended by the experts. Mild, low stress stimulation is more important.