How Much Vitamin B12 Should You Take Daily?

Vitamin B12 is a highly complex nutrient with numerous roles in the body. The recommended daily intake (RDI) of B12 for non-pregnant adults over 14 is 2.4 micrograms (mcg). Those who are pregnant need 2.6 mcg daily, while those who are breastfeeding need 2.8 mcg/day. 

B12 is required for red blood cell production, energy production, DNA synthesis, and the normal function of the brain and nervous system. However, daily requirements vary according to age, nutritional status, diet, lifestyle, genetics, and concurrent health conditions. 

Deficiency in B12 may lead to various health conditions, including anemia, fatigue, depression, and elevated homocysteine. Vitamin B12 is lower in patients with Parkinson’s disease, which has been associated with peripheral neuropathy, cognitive impairment, and faster disease progression. 

If your diet is not providing adequate B12 or your body cannot absorb it correctly, a B12 supplement may be the best way to support your body’s needs. 

This article will discuss the recommended dosages of B12 for adults according to their age, during pregnancy or breastfeeding, and whether they are vegan or vegetarian.

Your own requirements for vitamin B12 will depend on your age, lifestyle, diet, genetics, and other health circumstances. 

The Recommended Dietary Allowance (RDA) for vitamin B12 ranges from 1.4 to 3.0 μg per day based on the amount needed to maintain healthy hematological status and normal serum vitamin B12 values.

However, it’s important to understand that only around ~1.2%. of B12 taken orally will be absorbed into the bloodstream. 

This means that in order to get 2.4 μg of B12 per day, you would need to take 200 mcg by mouth daily (1.2% of 200 mcg = 6 mcg).

To get 6 mcg of B12 per day, you would need to take 500 mcg by mouth daily (1.2% of 500 mcg = 6 mcg)

Those who are already deficient in B12 will usually require supplementation with 1000-2000 mcg in order to absorb 12-24 mcg.

Patients with higher vitamin B12 concentrations have better health outcomes, while those with lower baseline vitamin B12 taking low-dose vitamins have higher risk of stroke, death, and coronary events. This suggests higher vitamin B12 doses may be essential for some patients.

Treatment with high-dose B12 in mice is also shown to modulate disease penetrance or progression in Parkinson’s disease, suggesting that high-dose B12 may be of therapeutic benefit.

So, how much Vitamin B12 should you take? 

For adults aged 50 and under, the RDA of Vitamin B12 is 2.4 mcg/day. 

Most people obtain this amount by eating everyday foods such as eggs, lean beef and poultry, dairy products, fish, and shellfish. Two eggs contain 1.2 mcg of B12, while 85g of salmon contains 2.7 mcg. 

Note: Certain conditions may affect your ability to absorb vitamin B12 properly, such as medications and gastrointestinal disorders. 

For adults aged 50 and over, the RDA of Vitamin B12 is also 2.4 mcg/day. 

Susceptibility to vitamin B12 deficiency changes throughout the life cycle, and older adults are among those with the highest risk of B12 deficiency.

However, US and Australian Nutrient Reference Values suggest that older adults may require higher intakes due to high rates of malabsorption due to gastritis and decreased stomach acidity that occurs with age, reducing the ability to absorb the form of B12 that occurs naturally in foods. The combination of malabsorption and poor dietary intake can speed the development of B12 deficiency. 

For these reasons, it is sometimes recommended that higher doses of B12 are obtained via supplementation, preferably from highly absorbable form of B12.

The WHO and US National Institutes of Health recommend a higher daily allowance of B12 in pregnant women than non-pregnant women to support fetal neurological development. The RDI for vitamin B12 during pregnancy is 2.6 mcg. 

The body’s need for B12 increases substantially during pregnancy. Vitamin B12 has many roles in the growth and development of the fetus, including the formation of red blood cells and the proper functioning of nerve tissue.

B12 deficiency in pregnancy can increase the risk of adverse pregnancy outcomes, including miscarriage, pregnancy loss, intrauterine growth restriction, low birth weight (<2500 g), neural tube defects, increased insulin resistance, higher susceptibility to chronic disease, and long-term deficits in the development of a child’s brain. 

B12 deficiency during pregnancy is very common, occurring in around 10–28% of uncomplicated pregnancies. For this reason, taking B12 during pregnancy is highly recommended.

The recommended daily intake of B12 in breastfeeding women is 2.8 mcg, but some authorities recommend 5.5 mcg per day. Supplementation is usually recommended to achieve these daily intakes or correct a known deficiency.

The RDI for breastfeeding women is higher than that for pregnant women due to the vital role that B12 plays in infant development.

Breastfed babies can become B12-deficient if the mother is also low in B12. Infants with B12 deficiency face numerous health risks, including anemia, abnormal skin and hair development, convulsions, weak muscle tone, failure to thrive, and mental developmental delay. 

Women at high risk or with known deficiency should be supplemented with vitamin B12 during pregnancy or while breastfeeding.

Vegans and vegetarians risk vitamin B12 deficiency as the nutrient is unavailable from plant sources. Moreover, its impact may be slow to detect because body stores of vitamin B12 can last years.

One review suggested that up to 86.5% of vegetarian adults were low in vitamin B12. 

Vitamin B-12 supplementation has been shown to improve B12 status and overall health in vegetarians with subnormal vitamin B-12 levels. 

While adults are generally advised to take 2.4 mcg of B12 per day, some authorities recommend that vegans take up to 6 mcg of supplemental B12 per day.

B12 deficiency is more prevalent in those with an MTHFR genetic mutation, namely the C677T variant. 

Although the exact reason for B12 deficiency in MTHFR is unclear, it is suggested that it may be due to either the abnormal metabolism of homocysteine in those with MTHFR—which depletes vitamin B12—or that MTHFR is typically associated with poor intestinal absorption of vitamin B12. 

Those with MTHFR gene mutations are advised to supplement with higher levels of vitamin B12. Beneficial results for the mother and fetus have been shown when 5 mcg of vitamin B12 is added to folate and vitamin B6 and taken during pregnancy. 

Hemodialysis patients with MTHFR who supplemented with 1500 mcg B12 and were shown to have lower homocysteine levels than those who did not supplement.

No. B12 is a water-soluble vitamin, which means it is not stored in the body. Excess vitamin B12 in the circulation usually exceeds the binding capacity of transcobalamins (transporting proteins) and is flushed out of the body in urine. For this reason, high doses are generally considered safe. 

Vitamin B12 has a low toxicity rating, so there is no Tolerable Upper Intake Level (UL). 

A daily intake of 4-7 mcg of B12 is associated with an adequate vitamin B-12 status, which has led some researchers to suggest that the current RDA of 2.4 mcg/day may be inadequate for optimal B12 levels. 

A dose-response study found that the most effective dose for normalizing vitamin B12 status in marginally deficient older adults was 500 µg/day. 

Vitamin B12 has numerous crucial bodily roles, including DNA and amino acid synthesis, fatty acid metabolism, cognitive function, healthy myelin formation, and nervous system maintenance. 

B12 works alongside folate as a coenzyme in one-carbon metabolism and also acts as a cofactor for methionine synthase (MS), which catalyzes the remethylation of homocysteine to methionine. This process contributes to the production of S-adenosylmethionine, which is required to synthesize neurotransmitters involved in healthy mood. 

S-adenosylmethionine (SAMe) is the sole methyl donor for the central nervous system, and researchers have linked vitamin B-12 deficiency to cognitive impairment and mental illness.

It’s also important to note that the amount of B12 you absorb from food or a supplement will depend on the form it is in. Some forms of B12 are absorbed less effectively than others.

According to RDA guidelines, 10-30% of adults aged 50+  B12 are likely to have malabsorption syndromes, which may mean they absorb as little as 1% of the ingested B12. These adults would need to take 240 mcg of B12 to absorb at least 2.4 mcg.

The three naturally-occurring forms of B12 shown in clinical studies to improve vitamin B12 status are Methylcobalamin, Hydroxocobalamin, and Adenosylcobalamin. These forms are also shown to be much more effective for some people than cyanocobalamin, the synthetic form of B12.

Those with MTHFR polymorphisms affecting B12 assimilation can improve their B12 status more efficiently by supplementing with one or more forms of B12, such as Methyl-Life’s® Active B12 Complete. This unique and highly bioavailable B12 supplement contains all 3 of the active B12 forms (hydroxocobalamin, methylcobalamin, and adenosylcobalamin). 

Methyl-Life’s B-Methylated-II provides both L-Methylfolate (3 mg) and Methylcobalamin (3.75 mg), both of which are required for healthy methylation. This is an excellent option for those who are pregnant, and/or those with MTHFR genetic mutations that suffer from low mood.  A higher dose of these nutrients is available as Methyl-Life’s® Methylfolate 7.5 mg + Active B12, which includes both methylfolate and two of the three active forms of B12: hydroxocobalamin and adenosylcobalamin.