30% Reduction in serum vitamin B6 levels documented in combined OCP users, per Palmery et al. 2013 meta-analysis
5 Key nutrients documented as depleted by combined oral contraceptives: folate, B6, B12, zinc, and magnesium
28 days Before conception when folate is needed for neural tube protection — often before a pregnancy is known

Which nutrients the pill depletes and why

Combined oral contraceptives contain both estrogen and progestogen. They affect nutrient metabolism through several mechanisms: they alter absorption, increase urinary excretion, or change how certain nutrients are used in metabolic processes. This was documented as early as the 1970s, and a 2013 meta-analysis by Palmery et al. in the European Review for Medical and Pharmacological Sciences collated the evidence across 34 studies.

The nutrients most consistently lower in OCP users include vitamin B6 (with one review noting a reduction of 30–36% in some studies), folate, vitamin B12, zinc, and magnesium. Selenium and CoQ10 depletion have also been reported, though the evidence is weaker. The magnitude of depletion varies by individual, dose, and duration of use. This does not mean deficiency is inevitable, but it does mean dietary and supplemental awareness is warranted.

Research note

Palmery M et al. (Eur Rev Med Pharmacol Sci, 2013) reviewed 34 studies examining OCP effects on nutritional requirements. The analysis found significant evidence of lower folate, B6, B12, and zinc in OCP users. The authors noted that individual variation is high — women with already marginal nutrient intakes or dietary restrictions (including vegetarian and vegan diets, which already carry B12 risk) are most likely to be clinically affected.

Does the depletion actually matter in practice?

For most healthy women eating a varied diet, the depletion is unlikely to cause frank deficiency. It matters most in specific situations: for women who were already eating a restrictive diet before starting the pill, for those using the pill long-term (several years or more), and critically, for those planning to conceive within months of stopping.

The B6 depletion may also be relevant to mood. Vitamin B6 is a cofactor in serotonin and dopamine synthesis. Some research suggests OCP users with low B6 may experience mood-related side effects at higher rates.

However, the evidence base here is observational and causality is difficult to establish. If you're managing low mood on the pill, discuss a B-complex supplement with your doctor alongside other options.

The folate gap: why it matters most if you plan to conceive

This is the most clinically significant implication of pill nutrient depletion. Neural tube closure occurs around 28 days after conception (when it fails, it causes conditions like spina bifida). Most women don't know they're pregnant at 28 days. Adequate folate before and immediately after conception is essential, which is why folic acid supplementation is recommended for all women planning to conceive.

Women who stop the pill to try to conceive may have lower folate levels than assumed. ACOG guidance recommends starting folic acid before trying to conceive. For women coming off the pill, it may be worth considering starting a supplement containing folate and B vitamins a few months before stopping, to allow levels to rebuild. Discuss timing with your doctor or midwife.

Practical steps

You don't need to stop the pill or start an elaborate supplement protocol. A basic B-complex that includes folate (ideally as methylfolate for those with MTHFR variants), plus ensuring your diet covers zinc-rich foods (meat, eggs, legumes, pumpkin seeds) and magnesium-rich foods (leafy greens, nuts, seeds), addresses the depletion for most women. If planning to conceive within the next year, speak to your doctor or pharmacist about starting a pre-conception supplement with adequate folic acid at least 3 months before trying.

The honest bottom line

Oral contraceptives are a safe and effective choice for the vast majority of women who use them. The nutrient depletion evidence is real but nuanced.

It does not mean the pill is damaging, and it does not mean you need to quit or take an expensive stack of supplements. What it does mean: women using the pill long-term benefit from being nutritionally aware, especially of folate, B6, and B12.

The broader nutrient awareness angle also connects to magnesium's role in women's hormones. Magnesium is a nutrient that many women are already low in before adding the pill's depleting effect. Getting bloodwork that includes B12 and folate at your annual check is a reasonable ask, regardless of contraception.

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What to ask your doctor

At your next pill review, ask whether your B12 and folate levels have been checked recently — and whether a B-complex supplement would be appropriate given your current diet. If you're planning to stop the pill to conceive in the next year, ask about pre-conception supplementation with folic acid and when to start. Never stop the pill without a contraception plan unless pregnancy is the intention.

Medical Disclaimer: This article is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

References

  1. Palmery M, et al. Oral contraceptives and changes in nutritional requirements. Eur Rev Med Pharmacol Sci. 2013;17(13):1804–1813. PubMed 23852908
  2. Berenson AB, et al. Prevalence of vitamin B12 deficiency in reproductive-age women. Obstet Gynecol. 2012;119(5):1024–1029. PubMed 22525916
  3. Lussana F, et al. Blood levels of homocysteine, folate, vitamin B6 and B12 in women using oral contraceptives compared to non-users. Thromb Res. 2003;112(1–2):37–41. PubMed 14653988
  4. Cagnacci A, et al. Influence of oral contraceptives on vitamin B12, folate and homocysteine levels. Contraception. 2015;91(5):403–408. PubMed 25640816