Can You Take Vitamin C and Vitamin B12 Together?
Usually, yes. Older claims that vitamin C lowers B12 have not been confirmed, and at least some were caused by assay artifacts.
The short answer
Standard doses of vitamin C and vitamin B12 can usually be taken together, and current official guidance does not require a fixed spacing interval.
Why it happens
Current official reviews do not confirm a clinically meaningful absorption conflict, so there is no reliable basis for a mandatory spacing interval.
What to do
Standard supplement doses can be taken together. Do not change a B12-deficiency treatment plan solely because of an online “two-hour rule.”
What the evidence actually showed
The older concern about vitamin C lowering B12 traces back to claims that have not been confirmed, and at least some of them were caused by assay artifacts — meaning the laboratory method used to measure B12 in older research could itself be affected by vitamin C, producing a false appearance of lower B12 rather than reflecting an actual biological drop. Current official reviews, looking at this with better methods, do not confirm a clinically meaningful absorption conflict between the two. This history explains why the popular two-hour rule persists online even though it does not hold up against present-day evidence.
When to ask a clinician
The general guidance that standard doses can be taken together is not a reason to self-manage a diagnosed B12 problem. If you have confirmed B12 deficiency, a malabsorption condition, or you receive B12 injections, your clinician's treatment plan should take priority over any timing rule you encounter, including the two-hour spacing idea. This distinction matters because general population guidance and an individualized treatment plan for a diagnosed deficiency are not the same thing, even when they both involve vitamin C and B12.
When this advice applies
This does not mean every megadose combination has been fully studied. If you have diagnosed B12 deficiency, malabsorption, or receive injections, follow your clinician’s plan.
Common questions
Does vitamin C lower vitamin B12 levels?
Older claims that vitamin C lowers B12 have not been confirmed, and at least some were caused by assay artifacts — meaning the way B12 was measured in older studies, rather than a real drop in B12, may have produced that appearance. Current official reviews do not confirm a clinically meaningful conflict.
Is there really a two-hour rule for vitamin C and B12?
No, that specific rule is not confirmed. Current official reviews do not confirm a clinically meaningful absorption conflict, so there is no reliable basis for a mandatory two-hour spacing interval. Standard supplement doses can generally be taken together.
Should I change how I treat B12 deficiency because of the two-hour rule I read online?
No. Do not change a B12-deficiency treatment plan solely because of an online two-hour rule. If you have diagnosed B12 deficiency, malabsorption, or receive B12 injections, follow your clinician's plan rather than an informal timing rule.
References
- Vitamin C — Health Professional Fact SheetNIH Office of Dietary Supplements · 2025
Updated July 31, 2026 · How to use this guidance