B12 vitamins are recommended during pregnancy if you have a deficiency.
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Everything You Need To Know About B12 During Pregnancy

It’s not quite the miracle energy-maker everyone thinks.

When you’re newly pregnant, you get endless advice, some of it helpful, some of it not (telling you to “make sure to get lots of sleep” when you might have pregnancy-induced insomnia isn’t exactly what you want to hear). One thing you probably know, from either your doctor or your friends, is that you’re supposed to take a prenatal vitamin, but some might also recommend a B12 vitamin during pregnancy. It sounds healthy enough, but do you need the additional B12 supplement during pregnancy?

If you’ve heard of B12, it may be because, for a brief time in the early ‘10s, various celebrities, including Madonna, Justin Timberlake, and Charlize Theron, were injecting themselves with this vitamin and touting it as a cure for everything from depression to exhaustion. (You won’t be surprised to learn that this isn’t a thing most people need to do — there’s little evidence to support the claims that injecting B12 gives you increased energy). But B12 is an important vitamin for everyone, and is particularly important if you’re pregnant or breastfeeding. So, what is B12, why do you need it, and how can you make sure that you get enough?

What is vitamin B12?

Vitamin B12 is one of eight B vitamins (not twelve, just to make things confusing — the substances known as B4, B10, and B11 aren’t officially considered vitamins). Mt. Sinai Hospital’s website notes that the eight “B” vitamins are necessary for many different bodily functions, including keeping your teeth, eyes, skin, and liver healthy.

Specifically, vitamin B12 “is important in developing red blood cells, and a B12 deficiency can result in a macrocytic anemia,” Dr. Zuri Hemphill-Bryant, an Atlanta-based OB-GYN, tells Romper via email. Macrocytic anemia occurs when your body doesn’t have enough normal red blood cells, and can cause symptoms including “muscle weakness and paresthesias” (paresthesias is the technical term for the “pins and needles” feeling on your skin).

Why is vitamin B12 important for pregnancy and postpartum?

Everyone needs this vitamin — but it’s especially crucial if you’re pregnant or breastfeeding a new baby. In a paper published in the medical journal Nutritions Review, researchers at UC-Davis noted that “most adults may tolerate a vitamin B12 deficient diet. . .for years without developing clinical symptoms of deficiency” but that “newborn infants have limited ‘hepatic reserves’” (that’s the term for liver cells which are necessary for the liver to function). Dr. Hempill-Bryant explains that babies born to B12 deficient mothers “will also be deficient in B12, especially if they are then exclusively breastfed.” A study in the Journal of Child Neurology found that the most severe cases of B12 deficiency can lead to “weakness, failure to thrive, afebrile seizure, developmental delay, nystagmus, tremors, and involuntary movement” among young babies.

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How can you make sure you’re getting enough B12?

Despite those scary possibilities, Hemphill-Bryant has reassuring info: “Most people get all of the B12 they need from their diets. B12 is mostly found in animal-based diets. So, if you are eating a varied diet and do not have a laboratory-documented vitamin B12 deficiency, you do not need additional supplementation.” However, she explains “people who subscribe to strict vegan or vegetarian diets are much more likely to be at risk of vitamin B12 deficiency, and they should take supplemental B12, especially when pregnant or trying to become pregnant.

Another group that’s at-risk for low B12 levels are those who have had gastric bypass surgery or have other stomach issues, such as ulcers. Finally, the biggest risk is for people who have “pernicious anemia,” a rare condition in which a person is unable to absorb any B12 through their stomach or intestines — people with this condition are the ones who actually need B12 injections.

Basically, if you’re eating a diet that includes shellfish, salmon, liver, and eggs, among other foods, you likely don’t need to stress too much about you or your baby having this deficiency. Your doctor can do a blood test if you’re concerned. And Hempill-Bryant reminds her patients that no matter what your diet is, you need a prenatal vitamin that includes folic acid, otherwise known as vitamin B9. B9 and B12 are two of the “Bs” that you just shouldn’t go without if you’re planning to welcome a new B (baby!) to your family.


Zuri Hempill-Bryant, MD,


Goraya JS, Kaur S, Mehra B. “Neurology of Nutritional Vitamin B12 Deficiency in Infants: Case Series From India and Literature Review.” J Child Neurol. 2015 Nov;30(13):1831-7. doi: 10.1177/0883073815583688. Epub 2015 May 7. PMID: 25953825.

Dror DK, Allen LH. “Effect of vitamin B12 deficiency on neurodevelopment in infants: current knowledge and possible mechanisms.” Nutr Rev. 2008 May;66(5):250-5. doi: 10.1111/j.1753-4887.2008.00031.x. PMID: 18454811.