For vitamin B12 oral intake, 1,000 mcg daily is both safe and sufficient.

Absorption Pathways

Guidelines from NIH suggest that we need 0.4 - 2.8 mcg B12 depending on our stage of life. The large difference between requirement and recommended supplemental intake arises from the different ways that vitamin B12 is absorbed in the body.

• Intrinsic factor in our stomach helps us to absorb about 2.0 mcg of B12 per meal. However, some people have pernicious anaemia, a condition in which they cannot make intrinsic factor and therefore have trouble absorbing B12 this way. This is more common in elderly individuals with impaired intestinal absorption.
• Passive diffusion allows about 1.2% of dietary B12 to enter the bloodstream, even in the absence of intrinsic factor. So in a tablet containing 1000 mcg, up to 12 mcg may be absorbed which is sufficient to meet the recommended daily amount.

Safety

No harmful effects have ever been shown from consuming too much vitamin B12, and no maximum dose has been identified. Vitamin B12 is water-soluble and excess vitamin will be rapidly excreted in the urine over the course of a few days.

However, take care with multivitamins and b-complex vitamins because vitamin B6 has a tolerable upper limit of 100 mg/day in adults, and excess B6 can be harmful.

See also: Can too much B12 be harmful?

Food sources of vitamin B12

Vitamin B12 in chicken eggs is poorly absorbed compared to other animal sources, so ovo-vegetarians are also advised to take B12 supplements.

Supplemental sources of vitamin B12

Oral doses of vitamin B12 of at least 1000 mcg are considered just as effective as intramuscular injection.

Vitamin B12 status among Canadians

A 2011 study of 5600 Canadians showed that about 4.6% of the population had low vitamin B12 status (<148 pmol/L in the blood).

Among Canadians, typical B12 concentration in the blood is 350 pmol/L when not taking supplements. On supplements, B12 concentration may rise to 550 pmol/L or higher.

For vitamin B12 oral intake, 1,000 mcg daily is both safe and sufficient.

Update: A recent randomized controlled trial of vegetarians and vegans who were marginally B12 deficient showed that 50 mcg B12 taken daily was sufficient to correct B12 status. Effect of two different sublingual dosages of vitamin B12 on cobalamin nutritional status in vegans and vegetarians with a marginal deficiency: A randomized controlled trial

Absorption Pathways

Guidelines from NIH suggest that we need 0.4 - 2.8 mcg B12 depending on our stage of life. The large difference between requirement and recommended supplemental intake arises from the different ways that vitamin B12 is absorbed in the body.

• Intrinsic factor in our stomach helps us to absorb about 2.0 mcg of B12 per meal. However, some people have pernicious anaemia, a condition in which they cannot make intrinsic factor and therefore have trouble absorbing B12 this way. This is more common in elderly individuals with impaired intestinal absorption.
• Passive diffusion allows about 1.2% of dietary B12 to enter the bloodstream, even in the absence of intrinsic factor. So in a tablet containing 1000 mcg, up to 12 mcg may be absorbed which is sufficient to meet the recommended daily amount.

Safety

No harmful effects have ever been shown from consuming too much vitamin B12, and no maximum dose has been identified. Vitamin B12 is water-soluble and excess vitamin will be rapidly excreted in the urine over the course of a few days.

However, take care with multivitamins and b-complex vitamins because vitamin B6 has a tolerable upper limit of 100 mg/day in adults, and excess B6 can be harmful.

See also: Can too much B12 be harmful?

Food sources of vitamin B12

Vitamin B12 in chicken eggs is poorly absorbed compared to other animal sources, so ovo-vegetarians are also advised to take B12 supplements.

Supplemental sources of vitamin B12

Oral doses of vitamin B12 of at least 1000 mcg are considered just as effective as intramuscular injection.

Vitamin B12 status among Canadians

A 2011 study of 5600 Canadians showed that about 4.6% of the population had low vitamin B12 status (<148 pmol/L in the blood).

Among Canadians, typical B12 concentration in the blood is 350 pmol/L when not taking supplements. On supplements, B12 concentration may rise to 550 pmol/L or higher.

For vitamin B12 oral intake, 1,000 mcg daily is both safe and sufficient.

Absorption Pathways

Guidelines from NIH suggest that we need 0.4 - 2.8 mcg B12 depending on our stage of life. The large difference between requirement and recommended supplemental intake arises from the different ways that vitamin B12 is absorbed in the body.

• Intrinsic factor in our stomach helps us to absorb about 2.0 mcg of B12 per meal. However, some people have pernicious anaemia, a condition in which they cannot make intrinsic factor and therefore have trouble absorbing B12 this way. This is more common in elderly individuals with impaired intestinal absorption.
• Passive diffusion allows about 1.2% of dietary B12 to enter the bloodstream, even in the absence of intrinsic factor. So in a tablet containing 1000 mcg, up to 12 mcg may be absorbed which is sufficient to meet the recommended daily amount.

Safety

No harmful effects have ever been shown from consuming too much vitamin B12, and no maximum dose has been identified. Vitamin B12 is water-soluble and excess vitamin will be rapidly excreted in the urine over the course of a few days.

However, take care with multivitamins and b-complex vitamins because vitamin B6 has a tolerable upper limit of 100 mg/day in adults, and excess B6 can be harmful.

Food sources of vitamin B12

Vitamin B12 in chicken eggs is poorly absorbed compared to other animal sources, so ovo-vegetarians are also advised to take B12 supplements.

Supplemental sources of vitamin B12

Oral doses of vitamin B12 of at least 1000 mcg are considered just as effective as intramuscular injection.

Vitamin B12 status among Canadians

A 2011 study of 5600 Canadians showed that about 4.6% of the population had low vitamin B12 status (<148 pmol/L in the blood).

Among Canadians, typical B12 concentration in the blood is 350 pmol/L when not taking supplements. On supplements, B12 concentration may rise to 550 pmol/L or higher.

For vitamin B12 oral intake, 1,000 mcg daily is both safe and sufficient.

Absorption Pathways

Guidelines from NIH suggest that we need 0.4 - 2.8 mcg B12 depending on our stage of life. The large difference between requirement and recommended supplemental intake arises from the different ways that vitamin B12 is absorbed in the body.

• Intrinsic factor in our stomach helps us to absorb about 2.0 mcg of B12 per meal. However, some people have pernicious anaemia, a condition in which they cannot make intrinsic factor and therefore have trouble absorbing B12 this way. This is more common in elderly individuals with impaired intestinal absorption.
• Passive diffusion allows about 1.2% of dietary B12 to enter the bloodstream, even in the absence of intrinsic factor. So in a tablet containing 1000 mcg, up to 12 mcg may be absorbed which is sufficient to meet the recommended daily amount.

Safety

No harmful effects have ever been shown from consuming too much vitamin B12, and no maximum dose has been identified. Vitamin B12 is water-soluble and excess vitamin will be rapidly excreted in the urine over the course of a few days.

However, take care with multivitamins and b-complex vitamins because vitamin B6 has a tolerable upper limit of 100 mg/day in adults, and excess B6 can be harmful.

See also: Can too much B12 be harmful?

Food sources of vitamin B12

Vitamin B12 in chicken eggs is poorly absorbed compared to other animal sources, so ovo-vegetarians are also advised to take B12 supplements.

Supplemental sources of vitamin B12

Oral doses of vitamin B12 of at least 1000 mcg are considered just as effective as intramuscular injection.

Vitamin B12 status among Canadians

A 2011 study of 5600 Canadians showed that about 4.6% of the population had low vitamin B12 status (<148 pmol/L in the blood).

Among Canadians, typical B12 concentration in the blood is 350 pmol/L when not taking supplements. On supplements, B12 concentration may rise to 550 pmol/L or higher.