Water-soluble vitamins

Vitamin B12

Nerves · red blood cells

Myelin synthesis, red blood cell production, methylation cycle.

Daily target

2.4 mcg

FDA Daily Value

Upper limit

None

No UL established

Catalog matches

supplements in our catalog

What Vitamin B12 does

B12 is required for two reactions: methionine synthase (regenerates methionine from homocysteine, needed for methylation) and methylmalonyl-CoA mutase (in odd-chain fatty acid metabolism). Absorption is uniquely complex — it requires intrinsic factor secreted by the stomach and is taken up in the terminal ileum. Status deteriorates slowly because the liver stores ~3–5 years' worth, but once symptoms appear, neurological damage may not fully reverse even with repletion. Untreated deficiency permanently damages the spinal cord (subacute combined degeneration).

Food sources of Vitamin B12

Approximate Vitamin B12 content per serving. Whole-food intake counts toward your daily total alongside any supplemental dose.

Food	Serving	Vitamin B12
Clams (cooked)	3 oz	85 mcg
Beef liver (cooked)	3 oz	70 mcg
Cooked salmon	3 oz	4.8 mcg
Beef (cooked)	3 oz	2.4 mcg
Greek yogurt	1 cup	1.3 mcg
Egg (whole)	1 large	0.5 mcg

Signs of Vitamin B12 deficiency

●Macrocytic anemia identical in appearance to folate deficiency
●Peripheral neuropathy: numbness, tingling, glove-and-stocking distribution
●Loss of vibration and position sense; ataxia
●Cognitive changes: memory loss, confusion, sometimes misdiagnosed as dementia
●Glossitis with smooth, beefy-red tongue

Who needs more Vitamin B12

Groups and situations where Vitamin B12 requirements rise or status commonly runs low:

●Vegans and most long-term vegetarians — B12 is virtually absent from plant foods
●Adults over 50 — atrophic gastritis reduces intrinsic factor production (~10–30% prevalence)
●Long-term proton pump inhibitor or metformin users
●Pernicious anemia, gastric bypass, ileal resection, Crohn's disease of the terminal ileum

Forms to avoid

Not all Vitamin B12 forms absorb equally well. The following forms are commonly used because they're cheap, but their bioavailability is materially lower than alternatives — watch for them on supplement labels:

cyanocobalamin

Formulate's product scoring penalizes these forms when they appear as the primary Vitamin B12 source — see the methodology page for the rubric.

How Vitamin B12 appears on labels

Supplement labels list Vitamin B12 under several names depending on the chemical form used. Any of these on an ingredients panel counts toward your Vitamin B12 intake:

vitamin b12
vitamin b-12
cobalamin
cyanocobalamin
methylcobalamin
hydroxocobalamin
adenosylcobalamin

Best supplements for Vitamin B12

Top-scoring supplements in our catalog that list Vitamin B12 on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.

Thorne

Vitamin B12

Thorne

Craving and Stress Support

Thorne

Methyl-Guard®

Thorne

MediClear-SGS™ - Vanilla

Thorne

Methyl-Guard Plus®

Thorne

Thyroid Health Complex (formerly Thyrocsin)

Thorne

Basic Nutrients 2/Day

Thorne

Basic Prenatal

Deep dive

For mechanism of action, dosing protocols, evidence grade, and interaction warnings on Vitamin B12, see the full encyclopedia entry:

Hydroxocobalamin Acetate encyclopedia entry →

Research on Vitamin B12

Peer-reviewed studies in our research database that reference Vitamin B12. Each entry links to a detailed methodology review.

Guides covering Vitamin B12

Long-form articles in our guide library that go deeper on Vitamin B12 — comparisons, protocols, and reviews.

Frequently asked questions

What is the daily target for Vitamin B12?

The fda daily value for Vitamin B12 is 2.4 mcg per day for adults. No Tolerable Upper Intake Level has been established.

What foods are highest in Vitamin B12?

Clams (cooked) (85 mcg per 3 oz); Beef liver (cooked) (70 mcg per 3 oz); Cooked salmon (4.8 mcg per 3 oz). See the food sources section below for the full list.

What is the best form of Vitamin B12 to supplement?

Methylcobalamin and adenosylcobalamin are the two coenzyme forms. Hydroxocobalamin has the longest serum half-life. Cyanocobalamin works for most healthy people but requires conversion and is usually penalized by Formulate's scoring. Sublingual or oral high-dose (1,000+ mcg) supplements work for most absorption deficits because passive uptake bypasses intrinsic factor.

What are the signs of Vitamin B12 deficiency?

Macrocytic anemia identical in appearance to folate deficiency; Peripheral neuropathy: numbness, tingling, glove-and-stocking distribution; Loss of vibration and position sense; ataxia.

Who is most at risk for low Vitamin B12?

Vegans and most long-term vegetarians — B12 is virtually absent from plant foods; Adults over 50 — atrophic gastritis reduces intrinsic factor production (~10–30% prevalence); Long-term proton pump inhibitor or metformin users.

Related water-soluble vitamins

Track your full intake

Formulate's free web app aggregates Vitamin B12 (and ~40 other nutrients) across every supplement in your stack — flagging underdoses, overlaps, and upper-limit overshoots in one view.

Track your intake free →

Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Targets and upper limits are general adult reference values; individual needs vary by age, sex, pregnancy status, and clinical context.