b12 sublingual vs injection Not all forms of are absorbed the same way.⁠, ⁠, One of the biggest differences between intramuscular B12 injections and supplementation comes down to how efficiently the body is able B12 Injections vs Oral Supplements:

The timing, severity, and accompanying symptoms can provide valuable clues about whether the supplement is genuinely responsible or whether another cause should be investigated

When the gastrointestinal tract does not function effectively, it may inhibit the release of B12 from the protein and the absorption that is meant to follow it

PMC / Aging Cell (2025) PMC12727671 Confirmed age-related NAD+ decline across multiple species (rodents, nematodes, and select human tissues including skin, liver, and brain)

[DOI] [PubMed] [Google Scholar] 177.Cummings DE, Purnell JQ, Frayo RS, Schmidova K, Wisse BE, Weigle DS

How Long Do The Results Of B12 Shots Last