Vitamin B12 Dosage: How Much Should You Take per Day?
Vitamin B12 is a water-soluble nutrient that’s required for many crucial processes in your body.
The ideal dose of vitamin B12 varies based on your gender, age, and reasons for taking it.
This article examines the evidence behind the recommended dosages for B12 for different people and uses.
Why do you need vitamin B12?
Vitamin B12 is an essential nutrient that plays a critical role in several of your body’s processes.
It’s necessary for proper red blood cell production, DNA formation, nerve function, and metabolism (1Trusted Source).
Vitamin B12 also plays a key role in reducing levels of an amino acid called homocysteine, high levels of which have been linked to chronic conditions like heart disease, stroke, and Alzheimer’s (2Trusted Source).
Additionally, vitamin B12 is important for energy production. However, there’s currently no evidence that taking B12 supplements increases energy levels in people who are not deficient in this nutrient (3Trusted Source).
Vitamin B12 is found mostly in animal products, including meats, seafood, dairy products, and eggs. It’s also added to some processed foods, such as cereal and nondairy milk.
Because your body can store B12 for several years, serious B12 deficiency is rare, but up to 26% of the population may have a mild deficiency. Over time, B12 deficiency can lead to complications like anemia, nerve damage, and fatigue.
Vitamin B12 deficiency can be caused by not getting enough of this vitamin through your diet, problems with absorbing it, or taking a medication that interferes with its absorption (4Trusted Source).
The following factors may put you at a higher risk of not getting enough vitamin B12 from diet alone (5Trusted Source, 6Trusted Source):
following a vegetarian or vegan diet
being over 50 years old
gastrointestinal disorders, including Crohn’s disease and celiac disease
surgery on the digestive tract, such as weight loss surgery or bowel resection
metformin and acid-reducing medications
specific genetic mutations, such as MTHFR, MTRR, and CBS
regular consumption of alcoholic beverages
If you’re at risk of deficiency, taking a supplement may help you meet your needs.
Summary
Vitamin B12 is an important nutrient that plays a critical role in your body. It’s mainly found in animal products, and some people may be at risk of not getting enough from diet alone.
Suggested dosages
The recommended daily intake (RDI) for vitamin B12 for people over 14 is 2.4 mcg (1Trusted Source).
However, you may want to take more or less, depending on your age, lifestyle, and specific situation.
Note that the percent of vitamin B12 your body can absorb from supplements is not very high — it’s estimated that your body only absorbs 10 mcg of a 500-mcg B12 supplement (7Trusted Source).
Here are some recommendations for B12 dosages for specific circumstances.
Adults under age 50
For people over 14, the RDI for vitamin B12 is 2.4 mcg (1Trusted Source).
Most people meet this requirement through diet.
For example, if you ate two eggs for breakfast (1.2 mcg of B12), 3 ounces (85 grams) of tuna for lunch (2.5 mcg of B12), and 3 ounces (85 grams) of beef for dinner (1.4 mcg of B12), you would consume more than double your daily B12 needs (1Trusted Source).
Therefore, supplementing with B12 is not recommended for healthy people in this age group.
However, if you have any of the factors described above that interfere with vitamin B12 intake or absorption, you may want to consider taking a supplement.
Adults over age 50
Older people are more susceptible to vitamin B12 deficiency. While relatively few younger adults are deficient in B12, up to 62% of adults over the age of 65 have less than optimal blood levels of this nutrient (8Trusted Source, 9).
As you age, your body naturally makes less stomach acid and intrinsic factor — both of which can affect the absorption of vitamin B12.
Stomach acid is necessary to access the vitamin B12 found naturally in food, and intrinsic factor is required for its absorption.
Due to this increased risk of poor absorption, the National Academy of Medicine recommends that adults over the age of 50 meet most of their vitamin B12 needs through supplements and fortified foods (1Trusted Source).
In one 8-week study in 100 older adults, supplementing with 500 mcg of vitamin B12 were found to normalize B12 levels in 90% of participants. Higher doses of up to 1,000 mcg (1 mg) may be necessary for some (10Trusted Source).
Pregnant women
Pregnant women have slightly higher vitamin B12 needs than the general population.
Low maternal levels of this vitamin have been associated with birth defects in infants (11Trusted Source).
Additionally, a large systematic review showed that B12 deficiency is associated with a higher risk of premature birth and low birth weight in newborns (12Trusted Source).
Therefore, the RDI for vitamin B12 during pregnancy is 2.6 mcg. This level can be met through diet alone or with a prenatal vitamin (1Trusted Source).
Breastfeeding women
Vitamin B12 deficiency in breastfed infants has been linked to developmental delay (13Trusted Source).
Additionally, B12 deficiency in infants can lead to irritability, decreased appetite, and failure to thrive (14Trusted Source).
For these reasons, the RDI for this vitamin for breastfeeding women is higher than that for pregnant women — namely 2.8 mcg (1Trusted Source).
Vegetarians and vegans
Vitamin B12 recommendations do not differ for people following a plant-based diet.
However, the RDI of 2.4 mcg for people under 50 years of age is much harder to meet on a vegetarian or vegan diet (1Trusted Source).
In a review of 40 studies on vitamin B12 in vegetarians, up to 86.5% of vegetarian adults — including older adults — were found to have low levels of vitamin B12 (15Trusted Source).
There are currently no government recommendations for B12 supplement dosages for vegetarians.
However, one study suggests that doses up to 6 mcg of vitamin B12 per day may be appropriate for vegans (16Trusted Source).
B12 for improved energy
Though vitamin B12 is commonly taken to increase energy levels, evidence showing that B12 supplements improve energy levels in people without a deficiency is lacking.
However, B12 supplements have been found to improve energy levels in those who are deficient in this nutrient (17Trusted Source).
One review recommended that those with vitamin B12 deficiency take 1 mg of vitamin B12 daily for a month, followed by a maintenance dose of 125–250 mcg per day (18Trusted Source).
People who have issues absorbing vitamin B12, such as those with Crohn’s disease or other gastrointestinal issues, may benefit from B12 injections, which bypass the need for absorption by the digestive tract (17Trusted Source).
B12 for memory and mood
It’s commonly thought that taking vitamin B12 can boost your memory and mood. However, there’s not a lot of evidence to support this theory.
Animal studies suggest that vitamin B12 deficiency has been associated with memory impairment. Yet, there’s currently no evidence that B12 supplements improve memory in humans who aren’t deficient (19Trusted Source).
In a large review, vitamin B12 supplements had no effect on depressive symptoms in the short term but may help prevent relapse over the long term (20Trusted Source).
There are no specific dosage recommendations for B12 supplements for mental performance or mood.
Summary
Optimal dosing of vitamin B12 varies by age, lifestyle, and dietary needs. The general recommendation for adults is 2.4 mcg. Older adults, as well as pregnant and breastfeeding women, require higher doses.
Potential side effects
Vitamin B12 is a water-soluble vitamin, meaning that your body excretes what you don’t need in your urine.
Because it’s relatively safe, no tolerable upper intake level (UL) has been set for vitamin B12. UL is considered the maximum amount of a substance that can be taken safely without side effects.
However, vitamin B12 has been shown to cause rare side effects in some cases.
Vitamin B12 injections may lead to skin conditions, such as acne and dermatitis (rash) (21Trusted Source).
High doses of B vitamins over 1,000 mcg have also been associated with complications in people with kidney disease (22Trusted Source).
Furthermore, extremely high blood levels of B12 in mothers was connected to a higher risk of autism in their children (23Trusted Source).
Summary
Though high doses of vitamin B12 supplements have been linked to rare side effects in certain populations, it’s generally safe, and there’s currently no recommended maximum amount for this vitamin.
The bottom line
Vitamin B12 is a nutrient that plays many essential roles in your body.
The RDI for vitamin B12 ranges from 2.4 mcg for adults to 2.8 mcg for breastfeeding women.
Most people meet these needs through diet alone, but older adults, people on strict plant-based diets, and those with digestive disorders may benefit from supplements, though dosages vary based on individual needs.
