Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| Methylcobalamin (B12) | Vitamin B6 (P5P) | |
|---|---|---|
| Category | Vitamins | Vitamins |
| Standard Dose | 1000-5000 mcg methylcobalamin daily (sublingual preferred) | 25-50mg P5P daily |
| Timing | Morning, sublingual for best absorption (bypasses intrinsic factor requirement). Can combine with methylfolate. | Morning with food. Often included in B-complex. |
| Cycle Duration | ongoing | ongoing |
| Evidence Level | strong_human | strong_human |
Methylcobalamin serves as a cofactor for methionine synthase, transferring a methyl group from 5-MTHF to homocysteine to regenerate methionine and subsequently SAMe. Adenosylcobalamin (the other active B12 form) is a cofactor for methylmalonyl-CoA mutase in mitochondrial energy production and odd-chain fatty acid metabolism. B12 is essential for myelin synthesis, DNA synthesis (thymidylate synthase pathway), red blood cell maturation, and neurological function. Deficiency causes megaloblastic anemia and irreversible subacute combined degeneration of the spinal cord.
1000-5000 mcg methylcobalamin daily (sublingual preferred)
Morning, sublingual for best absorption (bypasses intrinsic factor requirement). Can combine with methylfolate.
ongoing
Pyridoxal-5-phosphate (P5P) is the active coenzyme form of vitamin B6, required by over 150 enzymes. Key roles: transamination and decarboxylation of amino acids, serving as a cofactor for aromatic L-amino acid decarboxylase (converting 5-HTP to serotonin and L-DOPA to dopamine), glutamic acid decarboxylase (producing GABA), cystathionine beta-synthase (homocysteine transsulfuration to cysteine), serine hydroxymethyltransferase (one-carbon folate metabolism), glycogen phosphorylase (glycogenolysis), and aminolevulinic acid synthase (heme synthesis).
25-50mg P5P daily
Morning with food. Often included in B-complex.
ongoing
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