Overview
Absorption is boosted when B12 mixes with saliva.
Deficiency
- https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2022.972468/full
- https://journals.sagepub.com/doi/10.1177/03795721241229500
Is Oral Vitamin B12 as Effective as Intramuscular Injection?
American Family Physician
Oral vs. Intramuscular Vitamin B12 for Treating Vitamin B12 Deficiency
American Family Physician
- Dosage and Absorption Tips
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"Very high-dose B-12 is not recommended for people who do not have trouble absorbing B-12, as there may be side effects."
- "Most importantly, be aware that your body can only efficiently absorb a small amount of B-12 (about 2.4 mcg) at a time."
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- "To absorb more B-12, divide the dose over the course of the day and take separately from a B-12-containing meal."
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- "If you take a higher dose, such as 100 mcg, you will absorb only about 1% of the amount above 2.4 mcg."
- "Research suggests that very high-dose oral supplementation (typically 1,000 mcg daily) can effectively treat B-12 deficiency — even in people who have compromised absorption due to lack intrinsic factor (a cause of "pernicious anemia") or from gastrointestinal disease or bowel resection"