When comparing the different forms of B12 supplements, particularly adenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl), there are several factors you should consider, especially given your monthly cobalamin injections and current feelings of inadequacy.

Forms of Vitamin B12:

1. Methylcobalamin (MeCbl):

   • Function: Acts as a cofactor for methionine synthase, which is essential for DNA synthesis and homocysteine metabolism¹.
   • Benefits: Known to support neurological function and may help in cases of diabetic neuropathy².
   • Bioavailability: Can be taken orally or sublingually and has decent bioavailability; however, clinical evidence also shows no significant advantage over other forms in systemic absorption³.

2. Adenosylcobalamin (AdoCbl):

   • Function: Functions as a cofactor for methylmalonyl CoA mutase, important for myelin synthesis and energy metabolism in cells⁴.
   • Benefits: Particularly useful in addressing neurological manifestations associated with B12 deficiency¹.
   • Bioavailability: Converts internally into a usable form, like MeCbl. Effective for individuals requiring active coenzyme forms for specific enzymatic reactions⁴.

Clinical Evidence:

• Both MeCbl and AdoCbl are crucial for different biochemical reactions in the body, suggesting that they cannot substitute for each other entirely but can complement each other¹.
• There is evidence suggesting the equivalence of oral and injectable forms of B12 in alleviating deficiency³.
• Furthermore, there's little to no difference in absorption rates among different B12 forms from dietary supplements⁴.

Recommendations:

Given that you're feeling unwell on your current protocol of B12 injections:

• Combination Approach: You might benefit from a combined use of methylcobalamin and adenosylcobalamin to ensure both neurological and metabolic needs are met.
• Regular Supplementation: Consider supplementing more frequently than your monthly injections, possibly adding oral or sublingual B12 to maintain more consistent levels.
• Form Selection: A liquid form of either or both of these could provide better absorption if you face issues with pill swallowing or digestion.

Would you like me to search for specific product recommendations for liquid forms of methylcobalamin and adenosylcobalamin?

Footnotes

1. Vitamin B12 (Cobalamin) - StatPearls - NCBI Bookshelf ↩ ↩² ↩³

2. Methylcobalamin in Vitamin B12 Deficiency: To Give or not to Give? ↩

3. Office of Dietary Supplements - Vitamin B12 ↩ ↩²

4. Comparative Bioavailability and Utilization of Particular Forms of B12 Supplements With Potential to Mitigate B12-related Genetic Polymorphisms ↩ ↩² ↩³