How Much Vitamin B12 Should I Take, and How Much Is Too Much?

How Much Vitamin B12 Should I Take, and How Much Is Too Much?

Ever wonder why some prenatal supplements (including ours!) contain so much Vitamin B12? How much do you actually need for preconception and pregnancy? What happens if you take too much? Is this even safe?!

What does Vitamin B12 do?

Vitamin B12 is an essential nutrient for making red blood cells and DNA. It’s critical for regulating the function of your immune and nervous systems.

B12’s most prestigious role is in the methylation cycle, which co-stars Folic Acid. Methylation happens when nutrients such as Folic Acid, Vitamin B6 and Vitamin B12 donate a methyl group (a molecule combo of one carbon and three hydrogen), and transfer it to a protein, enzyme, hormone or right onto DNA. This is an important transaction because it detoxifies harmful chemicals, drugs, and hormone metabolites. It allows your DNA to replicate and activates genes from your DNA. Specifically, methylation controls gene expression and gene silencing. This means it’s the switch that turns individual genes on and off as needed.

Not having enough Vitamin B12 can cause a lot of problems, including abnormally large red blood cells (macrocytosis), anemia (pernicious anemia and macrocytic anemia), and in severe cases, psychosis and death. There are many symptoms of a Vitamin B12 deficiency to look out for:

  • fatigue and general weakness
  • shortness of breath
  • dizziness or light-headedness
  • brain fog
  • numbness or tingling
  • tongue swelling
  • bloating and/or diarrhea

The methylation cycle provides other benefits too—especially when it comes to pregnancy! As part of the process, it recycles a compound called homocysteine, which prevents levels from building up. This is important since excess homocysteine can cause breaks in DNA strands and increase oxidative stress. Big picture, high levels of homocysteine have been linked to pregnancy loss, preterm delivery, restricted fetal growth, preeclampsia and other cardiovascular complications.

High amounts of homocysteine have also been linked to neural tube defects in early pregnancy. This is when the tube that will form the earliest spinal cord and brain doesn’t close properly. It can cause spina bifida, paralysis, and even completely prevent the brain from developing.

Since Folic Acid and Vitamin B12 play leading roles in the methylation cycle, their close-knit relationship and their impact on homocysteine has some researchers suggesting that both should be taken as supplements to prevent neural tube defects.

Why is supplementing with Vitamin B12 important?

Your body can’t make Vitamin B12 on its own, so it needs you to supply it through food or supplements.

Dietary B12 is mostly found in animal products including meat, dairy, eggs and fish. That means that vegans and vegetarians will need a supplement to make sure they get enough B12 in pregnancy.

If you do eat these foods, you’ll then need your stomach acids free up the B12 so your body can use it. The downside of this process is that anything that compromises stomach acidity (like taking antacids or having gastric surgery) could prevent you from getting Vitamin B12 from food sources.

If all goes smoothly and your stomach acids to free up the B12, it can then attach to a protein called intrinsic factor, which facilitates B12’s absorption into the bloodstream. Typically, this leads to a B12 absorption rate of about 50 percent from food sources. But for those with pernicious anemia, an autoimmune condition that attacks intrinsic factor, the passive absorption of B12 is incredibly inefficient with only one percent being taken up from your food.

Another caveat to watch out for is if you’re taking Folic Acid solo. Most women and people with eggs who are trying to conceive or pregnant start taking Folic Acid supplements—it is super important after all. But high intakes of Folic Acid on its own can cover up an underlying Vitamin B12 deficiency. Both nutrients help create normal-sized red blood cells, so by taking Folic Acid when B12 levels are low, your red blood cells will look normal and not get flagged on routine blood work. Meanwhile, even though your Folic Acid status is great and red blood cells appear normal, not having enough B12 will cause homocysteine to build up, leading to neurological damage and changes in DNA function without you realizing it until symptoms set in. Most symptoms of Vitamin B12 deficiency can be reversed with supplementation, but if a deficiency goes on for too long, it can cause permanent neurological damage.

How much Vitamin B12 do I need?

First, it’s helpful to understand the RDA system. Short for “recommended dietary allowance,” these values are given to essential nutrients based on what is known about basic nutritional needs. The system was created during World War II to provide certain standards to the public for general health.

The RDA for Vitamin B12 for adults is set to 2.4 mcg (2.6 mcg in pregnancy and 2.8 mcg while breastfeeding) and represents the amount needed to prevent a damaging Vitamin B12 deficiency. In comparison, supplemental doses may seem really high, but that’s because your body only absorbs about one to two percent of Vitamin B12 from supplements.

In a supplement containing 50 mcg of Vitamin B12, you absorb about 1.5 mcg of that—and only 0.1 to 0.6 mcg if you have a problem with absorption or have pernicious (autoimmune) anemia. If your supplement contains 500 mcg, you’ll get about 10 mcg of that, and at a dose of 1,000 mcg you’ll absorb about 13 mcg.

Those amounts do put you over the 2.4 mcg RDA, but the tradeoff is worth it: you don’t want to mess around with low B12 levels. Though your body can store some Vitamin B12, whatever isn’t needed gets flushed via your urine. During pregnancy, you need more B12 because it gets stored by the placenta, which provides the fetus with enough of the vitamin to double mom’s B12 concentrations. After all, there is a lot of cell and DNA replication happening when you grow a human!

The bottom line is that Vitamin B12 is just too important to be low on, both for your preconception health and for fetal growth during pregnancy. Daily doses of 1,000 mcg have been reported as necessary in many cases to accommodate a wide range of Vitamin B12 use and storage in different people. Using higher doses in this range makes your supplement more reliable for ensuring you get enough Vitamin B12.

Is too much B12 toxic?

Vitamin B12 is a non-toxic compound and to date, there are no reported side effects of taking too much Vitamin B12. Along with there being no reports of it causing birth defects, cancers or any other type of toxicity, Vitamin B12 doesn’t even have an established “tolerable upper intake level” (UL), which is the amount that would cause an overdose or major unwanted side effects. The body will store some B12, but not in excessive amounts, and since it can easily dissolve in water, excess B12 gets excreted in urine.

What form of Vitamin B12 is best?

Methylcobalamin is a form of B12 that has a methyl group attached and all ready to go. It’s different from other forms of B12 such as cyanocobalamin as it doesn’t need to undergo any other changes to become ready for methylation.

Similarly, the active form of Folic Acid is called 5-Methyltetrahydrofolate (or 5-MTHF) and it too has a methyl group attached and ready to donate. Since your individual genetic code can alter the ability to process and transform these nutrients, taking the active forms allow you to bypass those extra steps.

By comparison, cyanocobalamin, a form of B12 commonly found in many supplements, has a cyanide group on the cobalamin instead of a methyl group. Although there’s no difference in how well either of these forms is absorbed, using the Methylcobalamin version can lead to 13 percent greater storage of B12 in the liver.

On top of Vitamin B12 and Folic Acid, methylation cycling is supported by Choline and Vitamin B6. So you want a prenatal supplement that offers all of these. That’s why we formulated both The Prenatal for eggs and The Power Prenatal for eggs to contain 1 mg of Folic Acid (including 600 mcg of the 5-MTHF form), 1,000 mcg of Methylcobalamin Vitamin B12, 25 mg of active Vitamin B6, and a high volume of Choline.

When it comes to the health of you and your unborn babe, it’s safer to ensure adequate Folic Acid and Vitamin B12 levels rather than fall short on either. Both are needed in preconception and pregnancy to make DNA for newly dividing cells, to process and eliminate dangerous estrogen metabolites and to keep homocysteine levels controlled. These nutrients are methylation besties—they need to stick together for optimal fertility health.