NutriStack
Combined Oral Contraceptive and Vitamin B12, a synergy.
Combined oral contraceptives are associated with lower serum vitamin B12 levels in multiple observational and review studies. Although clinical deficiency is uncommon, the drop can become meaningful in vegetarians, vegans, and long-term pill users, and matters for any planned pregnancy.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
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What the row says.
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At a glance
- Substances
- Combined Oral Contraceptive and Vitamin B12
- Pair type
- Synergy
- Evidence (highest tier)
- Moderate
- Source citations
- 2 sources
- Stack Score effect
- +2 to your Stack Score (per scored synergy row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Synergy · Moderate evidence
Synergy
What is happening. Combined oral contraceptives are associated with lower serum vitamin B12 levels in multiple observational and review studies. Although clinical deficiency is uncommon, the drop can become meaningful in vegetarians, vegans, and long-term pill users, and matters for any planned pregnancy.
Mechanism. COCs appear to lower serum holotranscobalamin and total B12 via altered B12-binding protein synthesis. The mechanism may also involve reduced intestinal uptake and increased catabolism in the liver.
Recommendation. Consider a daily B12 supplement (250-1000 mcg as methylcobalamin or cyanocobalamin) while on combined oral contraception, especially if you eat little animal protein or have been on the pill for many years.
Sources (2)
- Palmery M, Saraceno A, Vaiarelli A, Carlomagno G. Oral contraceptives and changes in nutritional requirements. Eur Rev Med Pharmacol Sci. 2013;17(13):1804-13. PMID 23852908
- Basciani S, Porcaro G. Counteracting side effects of combined oral contraceptives through the administration of specific micronutrients. Eur Rev Med Pharmacol Sci. 2022;26(13):4846-4862. PMID 35856377
Stack Score
How this pair moves the number.
Effect on the composite score
If both Combined Oral Contraceptive and Vitamin B12 are in the same stack, this pair applies +2 to your Stack Score (per scored synergy row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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