Oral Contraceptives and Vitamin B12: Is There An Issue for Vegans?

Oral Contraceptives and Vitamin B12: Is There An Issue for Vegans?

By | 2011-07-13T10:24:08+00:00 July 13th, 2011|Tags: |17 Comments

Several readers asked me about an article that appeared on the Vegan Mainstream website linking oral contraceptive use to vitamin B12 deficiency. The writer, who was depending in part on greens and sea veggies for vitamin B12 (somebody bring me my smelling salts, please) ended up with a B12 deficiency. Unable to reverse the deficiency with supplements, she finally was able to bring her blood levels back up after a doctor advised her to discontinue using oral contraceptives.

I can’t comment on this particular situation, but I can comment on the conclusion made in the article that “a vegan on birth control is a recipe for B12 trouble.”

The research does suggest that oral contraceptive use is associated with lower blood levels of vitamin B12 in many women (the vast majority of whom are not vegan, of course.) And, in omnivores using oral contraceptives, taking B12 supplements often doesn’t raise blood levels of this vitamin. But blood levels of B12 are not always a good indicator of actual nutrient status. Levels can sometimes be high even when a person is, in fact, deficient. And, in the case of oral contraceptive users, it appears that low blood levels of B12 may not always translate to deficiency.

Better indicators of B12 status are blood levels of compounds that require vitamin B12 for their metabolism. In vitamin B12 deficiency, levels of two compounds—methylmalonic acid and homocysteine—are elevated. In the studies of oral contraceptive users, even when serum B12 levels are low, these other more important changes don’t seem to occur.

Researchers believe that the lower blood levels of B12 are related to a decrease in certain proteins that bind B12—but that this doesn’t affect the amount of B12 being delivered to tissues. So while blood levels are low, B12 status is often fine.

This may not be the final word on oral contraceptives and vitamin B12, but it’s where the research stands right now. In their discussion of factors affecting vitamin B12 requirements, the Food and Nutrition Board (the U.S. government group that establishes nutrient recommendations) doesn’t even mention oral contraceptives. Of course, this doesn’t mean it’s impossible to develop a B12 deficiency while using oral contraceptives. Anyone who experiences a drop in vitamin B12 levels should talk with their doctor to decide if further testing is warranted.

But, if there is an issue here at all, it’s not really a vegan one. Given her lack of knowledge about sources of vitamin B12, it’s reasonable to believe that the writer of the Vegan Mainstream article had a true B12 deficiency. But, the problem was inadequate information about how to meet vitamin B12 needs on a vegan diet. Even if oral contraceptives were shown to impact vitamin B12 status, this shouldn’t be any more of a problem for vegans who take appropriate supplements than for anyone else.

So no, it isn’t true that “a vegan on birth control is a recipe for B12 trouble.” It is true that a vegan who doesn’t take adequate supplements is a recipe for B12 trouble.

As a quick refresher, any of the following strategies should meet the vitamin B12 needs of vegan adults:

  • Two servings per day of foods that are fortified with 1.5 or more micrograms of B12, OR
  • 25 micrograms or more of a chewable or sublingual B12 supplement every day, OR
  • 1,000 micrograms from a chewable or sub-lingual supplement twice per week.

Some references on oral contraceptive use and vitamin B12:

Shojania AM, Wylie B. The effect of oral contraceptives on vitamin B12 metabolism. Am J Obstet Gynecol 1979;135(1):129-34.

Gardyn J, Mittelman M, Zlotnik J, Sela BA, Cohen AM. Oral contraceptives can cause falsely low vitamin B(12) levels. Acta Haematol 2000;104(1):22-4.

Carmel R. Mild transcobalamin I (haptocorrin) deficiency and low serum cobalamin concentrations. Clin Chem 2003;49(8):1367-74

Riedel B, Nexo E, et al. Effects of oral contraceptives and hormone replacement therapy on cobalamin status. J Inherit Metab Dis 2003;23(supl):127

Rosenthal HL, Wilbois RP. Influence of oral contraceptive agents on vitamin B12 absorption and plasma level. Fed Proc 1975:34:905.

Sutterlin MW, Bussen SS, Rieger L, Dietl J, Steck T. Serum folate and Vitamin B12 levels in women using modern oral contraceptives (OC) containing 20 microg ethinyl estradiol. Eur J Obstet Gynecol Reprod Biol 2003;107(1):57-61.

Lussana F, Zighetti ML, Bucciarelli P, Cugno M, Cattaneo M. 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.

Vakur Bor, M. Do we have any good reason to suggest restricting the use of oral contraceptives in women with pre-existing vitamin B12 deficiency? Eur J Obstet Gyn Repr Biol 2004;115:240-241.


  1. Ali Dark July 13, 2011 at 10:43 am - Reply

    Hi there. Thanks for doing the research. I have a related question about finding my own B12 status. What would you recommend?


    • Ginny Messina July 15, 2011 at 2:02 pm - Reply

      Ali, if you have reason to believe that your B12 levels are low, I’d talk to your doctor about it and ask what he/she recommends as the most reliable test. Just testing blood levels is fine if you aren’t having any symptoms of B12 deficiency.

  2. Mark Osborne July 13, 2011 at 12:38 pm - Reply

    Thanks Ginny. I read that article (I’ve been researching B12 recently) and it was the first I had heard about oral contraception being a potential issue. I agree that a lack of understanding and insufficient supplementation were probably the core issues.

    On a related note – should we be concerned that the cyanocobalamin form of B12 found in most supplements delivers you a small dose of cyanide along with your B12?

    • Ginny Messina July 15, 2011 at 2:04 pm - Reply

      I don’t think so. It’s a really tiny amount of cyanide. I still recommend cyanocobalamin over methylcobalamin since the latter may be less stable.

  3. Vegans and Birth Control Pills July 13, 2011 at 1:33 pm - Reply

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  4. Erin July 13, 2011 at 2:21 pm - Reply

    My regular vegan multivitamin says that it contains 100% of B12. Do I still need the sublingual? Thanks!

    • Ginny Messina July 15, 2011 at 2:05 pm - Reply

      I would consider adding the sublingual. When you get all of your B12 from one single dose, the absorption may not be adequate. That’s why, for people who are taking B12 supplements once a day, we recommend 25 micrograms–which is much higher than the RDA.

  5. Ellie July 14, 2011 at 3:05 am - Reply

    For details of B12 absorption, go to dietarytruth.com and click on B12 and Beyond. The table is also available at veganhealth.org along with recommendations for other essential nutrients.

  6. 404 Not Found July 14, 2011 at 6:04 am - Reply

    […] Ginny and Jack shouldn’t have to do this sort of work, but I’m glad they do; this movement would be hosed if they weren’t out there. Support their essential work and go buy their great new book, and do your part to strike a blow against vegan nutritional quackery. Link. […]

  7. Robyn July 14, 2011 at 1:41 pm - Reply

    Thanks so much for the article Ginny; I’m not so worried now about moving more toward a vegan diet. Great info!

  8. […] Oral Contraceptives and Vitamin B12: Is There An Issue for Vegans? […]

  9. annie July 27, 2011 at 5:27 pm - Reply

    thank you for having this wonderful website. i have had b12 issues for many years – since my early 20s and i take supplements every day and have for almost 40 years.

  10. Jano July 28, 2011 at 4:05 am - Reply

    Hi Ginny, how about holotranscobalamin (active B12) as sufficient B12 deficiency indicator instead of methylmalonic acid and homocysteine? I read an article a few years ago, suggesting that that should be telling enough. Here’s the link: http://www.clinchem.org/cgi/content/full/49/12/2076 Could the contraceptives affect holotranscobalamin levels as well?

    • Ginny Messina August 8, 2011 at 5:15 pm - Reply

      Yes, I believe that holotranscobalmin is another good test for B12 status, although I don’t know how widely available it is. And in one of the studies on birth control pills, transcobalamin levels were decreased, but again, there didn’t seem to be any functional changes in B12 status.

  11. Julia Castro October 25, 2011 at 9:17 am - Reply

    Hi I have recently been diagnosed with Aplastic Anemia. I have been on birth control pills with 35 mg of estrogen for only 2 days now but feel like I have had a sudden problem with red blood cell and glucose related problems. Do you think it is safe for someone with AA to take BC pills? I feel like stopping them now. I started to avoid having a period for the platelets level reasons, but if they are going to mess with my RBC counts and hemoglobin levels i am not sure now.

  12. Zarah July 11, 2012 at 8:44 pm - Reply

    I was wondering, is there any merit to maca containing B12? On the Vega website it said maca had 70%, and multiple websites agree, but is it really true? I’ve heard to many people swearing by nori and unwashed vegetables to instantly believe, so I just wanted to ask a reliable source.

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