Is it possible to take an overdose of vitamin b12 during pregnancy?

Is it possible to take an overdose of vitamin b12 during pregnancy?

Pregnancy is one of the most exciting (and scary!) times of any woman’s life. There’s so much to plan and prepare for: the nursery, the stacks of diapers, the right stroller, a name…

But there’s one thing that’s much more important than all the baby paraphernalia: your health.

Whether you’re pregnant or just planning to start a family, one of your first priorities should be to make sure you’re getting adequate vitamin B12. Many people have no idea just how important this one vitamin is - especially for moms-to-be.

Unfortunately, there’s a lot of conflicting information out there about the so-called possibility of taking an overdose of B12 during pregnancy. In reality, the risk of a B12 deficiency is both far more prevalent - and dangerous.

Here’s why.

What is vitamin B12?

There are eight B vitamins (known as the B complex) and every one of them has an important role in our daily function. The complex includes thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9) and cobalamin (B12). Keep in mind that not all brands of B12 are created equal. 

Do you want the BEST B complex? We recommend trying Methyl-Life's Active B12 Complete formula. Methyl-Life® was the first manufacturer to combine all 3 active forms of B12 into a single tablet for effective, full-spectrum activity. Best of all, our B12 complete formula has all active forms of B12 (even the rarer forms). You can purchase our B12 complete by CLICKING HERE.   

Together, these vitamins help your body break down glucose (blood sugar) and create energy in the form of ATP molecules. ATP is like the ‘fuel’ that powers the tiny engines within every one of your body’s cells.

Also Read: MitoQ Product Description

So, why is B12 so important?

Like the other B vitamins, B12 is also required for energy production and mental alertness. It’s responsible for the body’s metabolism of fats and carbohydrates, and is often promoted for boosting athletic performance and endurance. It plays a major role in maintaining the health of the nerves and blood cells. It’s absolutely crucial for the making of DNA and RNA, the genetic material in all cells.

B12 is also the only B vitamin synthesized by bacteria rather than by plants. To absorb B12, your gut must produce a substance called intrinsic factor, a glycoprotein made by the parietal cells of the gastric mucosa[1]. During digestion, the hydrochloric acid in your stomach releases B12 from protein, where it then combines with intrinsic factor.

This rather complex metabolic pathway means two things: first, if your body lacks intrinsic factor, you will not be able to absorb B12 properly. This can result in a B12 deficiency.

Second, the only way to ensure proper uptake is by taking the most bioactive form of the vitamin. Bioactive simply means that the B12 has already been converted into a form that can be absorbed and used by the body’s cells immediately. Supplementary B12 should require minimal breakdown in order to be effective.

Also Read: Do We REALLY Need to Test for MTHFR Variants?

Why do women need B12 during pregnancy?

Vitamin B12 is crucial for normal cell division and differentiation, as well as the development and myelination of the central nervous system. Numerous studies have linked low vitamin B12 status in infancy to poor growth and neurodevelopment, plus many other health risks.

These are some of the many reasons B12 supplementation during pregnancy is so important...

  • Taking B12 helps prevent deficiency
    Research suggests that B12-deficiency is highly prevalent among pregnant women, affecting three-quarters of pregnancies in some populations. This is very concerning because B12 deficiency has been associated with both lower birth weight (<2,500 g) and preterm birth (length of gestation <37 weeks).
There is also evidence that low maternal B12 levels are associated with increased risk of preterm birth, and that the risk of preterm birth is particularly high if the mother is deficient in B12 at some stage during pregnancy.
  • B12 is required for brain development
  • Brain development starts from conception, and a baby’s brain undergoes rapid growth while in the womb.This is also the period when most of the myelination of the brain occurs. Even moderate vitamin B12 deficiency has been associated with demyelination
  • and brain atrophy[3]. Numerous case studies have shown the harmful effects of severe vitamin B12 deficiency on the developing infant brain, such as decreased cognitive performance.
  •  B12 helps prevent neural tube defects
    Children born to mothers who have low blood levels of vitamin B12 both before and after conception may have an increased risk of a neural tube defect. Neural tube defects affect the brain and spinal cord. They include conditions such as spina bifida (which can result in partial paralysis) and anencephaly, in which the brain and skull are severely underdeveloped. One study showed that women with the lowest B12 levels were five times more likely to have a child with a neural tube defect.
  • B12 reduces homocysteine
    Homocysteine is an amino acid that has been implicated in the risk of complications involving the placenta, such as preeclampsia, placental abruption, fetal growth restriction, and miscarriage[5]. High serum levels of homocysteine and low serum levels of B12 have been associated with reduced cognitive function.

One particular study found that homocysteine concentration in the early to mid-second trimester was associated with increased risk of these placenta-mediated complications, along with a higher risk of smaller babies, preeclampsia, placental abruption, and pregnancy loss. In some higher-risk groups, homocysteine was particularly associated with increased odds of preeclampsia. Researchers concluded that high-risk pregnancy may be linked to the MTHFR genetic mutation.

B12 works alongside folate and vitamin B6 to maintain normal concentrations of homocysteine in the bloodstream. Supplementation of B12 or folic acid helps to reduce homocysteine and may help in increasing birth weight and length of gestation.

  • B12 supports healthy mood during pregnancy
    Sufficient vitamin B12 is required for methylation, which in turn is necessary for the production of serotonin as well as other monoamine neurotransmitters and catecholamines.

Serum levels of vitamin B12 play an important role in cognitive and mental health. Studies suggest that up to 30% of patients hospitalized for depression are deficient in B12, and that B12 concentrations in blood are generally lower in depressed patients than nondepressed patients. This may play a key role in reducing the onset of post-natal depression in mothers.
Needless to say, supplementation with B12 should be a priority for all pregnant women. But how much?

How much B12 should I take during pregnancy?

The National Institute of Health recommends that women who are pregnant or breastfeeding take at least 2.8 micrograms (mcg) of B12 per day. However, studies have shown that high doses of oral B12 supplements (up to 2 mg or 2,000 mcg) are safe and effective, especially when treating B12 deficiency.

This is because your body will only absorb as much B12 as it needs. Any excess will be flushed out in your urine.

In any case, it’s always important to speak with your doctor before taking additional B12 during pregnancy.


It is possible to take an overdose of vitamin B12 during pregnancy?

There is no upper limit on B12 because of its “low potential for toxicity”. As mentioned above, any excess will be flushed out. Very small amounts are stored in body tissues and most vitamins - including B12 - don’t have an upper-level limit.

This amount of B12 you absorb depends on a number of factors:

  • the form of the B12
  • the efficacy of your genetic enzymes, and
  • the production of intrinsic factor in your stomach

No adverse effects have been linked with high intake of vitamin B12 in healthy people.

Recently, concerns about ‘overdosing’ on B12 came to light after a 2016 study reported on a link between too much B12 supplementation and autism. It appeared that women who took too much folate and vitamin B12 during pregnancy were 17.6 times more likely to have children who were later diagnosed with an autism spectrum disorder

However, of the 1,391 mothers involved in the study, only 95 had blood levels of B12 that were considered “excessive” by World Health Organization measures. And of those 95 mothers, only 15 had children who were diagnosed with an autism spectrum disorder. 

It also appeared that the mothers who had “excess” levels of BOTH vitamin B12 and folate who were most at risk: nearly half of those women had children who were diagnosed. This led the researchers to suggest that the mothers may have taken too many supplements, or that their bodies simply absorbed more, or metabolized them too slowly.

It’s worth noting that excess B12 blood serum levels can come from taking the common, cheap form of B12, cyanocobalamin, which for many does not convert into an active form the body needs to absorb and use - therefore it does not get transported for cellular use (and is instead floating around in the bloodstream without positive effect).

More importantly, the researchers emphasized that the results of the study were no reason to deter mothers from taking prenatal vitamins: if anything, they urged mothers to maintain their B12 intake.

The overriding message is that yes, pregnant moms definitely DO need B12. The risk of overdosing on B12 is almost non-existent. The risk of B12 deficiency is not only far more common, but far more deadly. 

So, what type of B12 should I take during pregnancy?

The health and wellness market is swamped with B12 supplements - but not all of them are effective!

  • A B12 supplement should be sublingually absorbed via the mucous membranes in the mouth. Look for B12 spray or tablets that are placed under the tongue and allowed to dissolve.
  • B12’s complex metabolic pathway means that the only way to ensure proper uptake is by taking the most bioactive form of the vitamin. Bioactive simply means that the B12 has already been converted into a form that can be absorbed and used by the body’s cells immediately.

    Most B12 supplements are available in two primary forms: methylcobalamin or cyanocobalamin. The less well-known types of B12 include Hydroxocobalamin and Adenosylcobalamin.


Methylcobalamin is a bioactive form of B12 that requires little to no conversion and crosses easily through every part of B12’s metabolic pathway.
Methylcobalamin helps in synthesis of methionine and S-adenosylmethionine (SAMe). It is also required to maintain integrity of myelin, neuronal function, proper red blood cell formation and DNA synthesis. It may also help in lowering homocysteine levels and reducing the risk of anemia.


This synthetic (man-made) form of B12 is often used in supplements because it’s cheaper. When ingested, cyanocobalamin is first converted into hydroxocobalamin and then undergoes conversion to become both methylcobalamin and adenosylcobalamin, the two active forms of vitamin B12. However, cyanocobalamin not only contains a cyanide molecule but is much more difficult for the body to absorb due to its complex breakdown process. 

Genetically, some cannot tolerate this form of B12 in higher doses because their bodies don’t do the conversion.


This is a more rare but also biologically active form of B12. It’s a precursor to methylcobalamin and often recommended in conditions where B12 cannot be properly absorbed in the gut. It’s known to be the most well-tolerated form of active B12.
Hydroxocobalamin is essential for DNA replication and synthesis, proper function of the nervous system, cellular energy, as well the conversion of homocysteine into methionine. It’s known to help with brain fog, pernicious anemia and for clearing excess peroxynitrites.


Adenosylcobalamin is stored in the mitochondria and selected when the body requires a biologically active form of vitamin B12 for fast energy production. Adenosylcobalamin helps in muscle recovery, myelin sheath integrity, and reduces the risk of anemia.
As with methylcobalamin and hydroxocobalamin, adenosylcobalamin does not need to be converted by your genes or enzymes in order to be available for use. It’s also known as a scavenger that helps to clear out extra nitrous oxide and peroxynitrite in the body and convert it back into methionine.

Browse some of our products from our store

Pregnancy Bundle Chewable Methylated Multi + L-Methylfolate 2.5 mg + Hydroxocobalamin Supplements
5 mg B12 Complete Vitamins
1 mg L-Methylfolate Supplement
2.5 mg Hydroxocobalamin Supplement

Recommended B12 supplements for pregnancy

Methyl-Life™ Chewable Methylated Multivitamin + Cognitive is a comprehensive multivitamin supplying a healthy dose of active B12 (as hydroxocobalamin) plus other nutrients. Designed to promote healthy pregnancy and protect against neural tube defects, this multivitamin contains L-Methylfolate as well as a host of B vitamins and their cofactors, TRAACS® minerals, Vitamins A, D3, E, and bioactive K2.

It includes bioactive folate as L-Methylfolate and B12 in the form of well-tolerated hydroxocobalamin to promote the body’s production of glutathione, your most powerful antioxidant AND to help with the baby’s neural tube development. This multivitamin also supports natural energy production with a new ATP energy combination, Panmol® NADH + MicroActive® CoQ10.

Methyl-Life’s™ Chewable Methylated Multivitamin + Cognitive is a fantastic prenatal supplement and even suitable for children at a lower dose (1-2 tablets instead of 3). Note: this multivitamin contains no iron or Vitamin C as these nutrients often require specialized dosing from doctors.

It’s got a delicious Chocolate Raspberry flavor that most absolutely love - one company described it as a “sought after one of a kind product”. Treat your health to a tasty vitamin supplement and improve your quality of life.



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