Many people turn to vitamin B12 supplements for energy or mental clarity, yet clinical experience often shows uneven results between patients taking the same dose.
A new review published in Cureus, led by Dr. Liji Thomas and reviewed by Lauren Hardaker, suggests that the form of B12 might play a role, although researchers stress that current evidence remains limited.
How the body processes different B12 forms
Vitamin B12 from food must pass through several digestive steps before entering the bloodstream, where it supports cell division, nerve function and metabolic activity.
Synthetic cyanocobalamin needs an additional conversion before becoming active, and some individuals may process it less efficiently.
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Early studies indicate that methylcobalamin, already active in its structure, may be retained better in the liver, though findings are still mixed.
In clinical laboratories, serum levels below roughly 150 pg/mL often prompt further evaluation for malabsorption rather than low intake alone.
Subtle symptoms including tiredness, tingling or mild balance problems may appear long before significant neurological injury is detected.
Who is most vulnerable to deficiency
Patterns commonly reported in outpatient clinics include higher risk among older adults, people with gastrointestinal disorders and those who avoid animal products.
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Long-term use of medications such as metformin or acid-reducing treatments may also reduce circulating B12.
The review notes that many individuals meet dietary recommendations yet still show low levels due to impaired utilisation.
What current evidence suggests about supplement choices
Both methylcobalamin and cyanocobalamin raise serum levels, but early findings suggest potential advantages for methylcobalamin in people with absorption or metabolic challenges.
The authors emphasise that outcome data remain incomplete, and individual responses vary. Clinicians may increasingly tailor supplementation as research clarifies long-term effects.
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Sources: News Medical and Cureus
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