Supplement encyclopedia

Vitamin B12

Name: Vitamin B12
Creator: Pillintrip Editorial Team

Written by Pillintrip Editorial Team Updated October 30, 2026

Vitamin B12 is necessary for normal bodily functions. Reliable food sources and supplements are especially important with a fully plant-based diet.

Recheck the conclusions and examine the sources before choosing a supplement.

Main conclusion

Potential benefits

B12 matters primarily as a reliable part of the diet, particularly a vegan diet. With adequate status, a universal energy boost cannot be promised. One small experiment found increased peak cycling sprint power in men. [1] [2] [3]

What was studied

Power in a short cycling sprint: Three days on each regimen; seven days between periods; B12 intake on a plant-based diet: 12 weeks; Usual sleep: 14 days. [1] [2] [3]

How to obtain it from food

Effects and studied questions

Goal or question	Result	Confidence	Studies	Population studied	Key sources
Power in a short cycling sprint	There is a preliminary sports signal; it is too early to regard B12 as a universal energy supplement on this basis.Peak power in a Wingate series: 764.1 versus 734.2 W, about +30 W or +4.1%. This is a short high-intensity test, not prolonged endurance.	2/5	1One direct trial described; the count refers to the named publication, not the entire literature.Short-Term Methylcobalamin Supplementation Is Associated with Changes in Anaerobic and Cognitive Performance in Amateur Cyclists: A Randomized Crossover Trial ↗	18 male recreational cyclists; all completed both periods	Short-Term Methylcobalamin Supplementation Is Associated with Changes in Anaerobic and Cognitive Performance in Amateur Cyclists: A Randomized Crossover Trial ↗
B12 intake on a plant-based diet	A vegan diet requires a reliable B12 source: fortified foods or a supplement; the studied regimens are a separate reference.B12 status markers improved with both regimens. There was no placebo without B12; equal clinical effectiveness of the regimens was not established. Changes in tests do not imply increased energy with adequate B12.	3/5	1One direct trial described; the count refers to the named publication, not the entire literature.Effect of two different sublingual dosages of vitamin B(12) on cobalamin nutritional status in vegans and vegetarians with a marginal deficiency: A randomized controlled trial ↗	40 vegans and vegetarians with borderline B12 levels	Effect of two different sublingual dosages of vitamin B(12) on cobalamin nutritional status in vegans and vegetarians with a marginal deficiency: A randomized controlled trial ↗
Usual sleep	This experiment does not provide convincing support for improved sleep with adequate B12.Actigraphy found no significant changes in sleep duration, sleep onset time or sleep efficiency relative to the pre-supplement period. There was no placebo.	1/5	1One direct trial described; the count refers to the named publication, not the entire literature.Lack of association between serum vitamin B12 and nocturnal sleep parameters following cyanocobalamin supplementation in healthy adults ↗	14 adults with baseline B12 above the authors' deficiency threshold; one participant lacked final-week data	Lack of association between serum vitamin B12 and nocturnal sleep parameters following cyanocobalamin supplementation in healthy adults ↗

The study count refers to the cited source. Reviews with overlapping trials and outcomes from one study are not added together.

Guidance for each goal

Power in a short cycling sprint

Confidence2/5

There is a preliminary sports signal; it is too early to regard B12 as a universal energy supplement on this basis.

Study findings. Peak power in a Wingate series: 764.1 versus 734.2 W, about +30 W or +4.1%. This is a short high-intensity test, not prolonged endurance.

Studied regimen1 mg/daySublingual methylcobalamin

Duration and populationThree days on each regimen; seven days between periods18 male recreational cyclists; all completed both periods

The confidence scale assesses the reliability of this conclusion, not the probability of an individual result.

B12 intake on a plant-based diet

Confidence3/5

A vegan diet requires a reliable B12 source: fortified foods or a supplement; the studied regimens are a separate reference.

Study findings. B12 status markers improved with both regimens. There was no placebo without B12; equal clinical effectiveness of the regimens was not established. Changes in tests do not imply increased energy with adequate B12.

Studied regimen50 mcg daily or 2000 mcg once weeklySublingual vitamin B12

Duration and population12 weeks40 vegans and vegetarians with borderline B12 levels

The confidence scale assesses the reliability of this conclusion, not the probability of an individual result.

Usual sleep

Confidence1/5

This experiment does not provide convincing support for improved sleep with adequate B12.

Study findings. Actigraphy found no significant changes in sleep duration, sleep onset time or sleep efficiency relative to the pre-supplement period. There was no placebo.

Studied regimen3 mg/dayOral cyanocobalamin

Duration and population14 days14 adults with baseline B12 above the authors' deficiency threshold; one participant lacked final-week data

The confidence scale assesses the reliability of this conclusion, not the probability of an individual result.

How to read the confidence scale 1–5

The rating considers study quality, directness and applicability to the stated group and regimen. It is an editorial scale, not the probability of an individual result.

Total intake reference values

Group	Amount	Type
Adults aged 19 and over	2.4 mcg/day	RDA_total_intake
Pregnancy	2.6 mcg/day	RDA_total_intake
Breastfeeding	2.8 mcg/day	RDA_total_intake

Vitamin B12 — Health Professional Fact Sheet (NIH ODS) ↗

Safety and limitations

Standard oral B12 is generally well tolerated. Use in cobalt allergy is discussed individually. Metformin and acid-reducing medicines may lower B12 status. The absence of an established upper limit does not imply that every dose is safe. Metformin, proton pump inhibitors and H2 blockers may lower B12 status. With neurological symptoms and suspected deficiency, timely assessment of the cause and selection of a repletion regimen matter.

Vitamin B12 — Health Professional Fact Sheet (NIH ODS) ↗ · Vitamin B(12) Supplementation: Is More Always Better? ↗ · Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial ↗ · Short-Term Methylcobalamin Supplementation Is Associated with Changes in Anaerobic and Cognitive Performance in Amateur Cyclists: A Randomized Crossover Trial ↗

Forms

Cyanocobalamin: Studied for oral repletion; levels and symptoms determine whether the regimen applies. Methylcobalamin: Used in the short cycling sprint trial; the form's name does not establish general superiority over other B12 forms. Sublingual products: The route of administration alone does not guarantee a better clinical effect.

Food sources

B12 is found in fish, shellfish, liver, eggs and dairy products. A 200 g portion of 2% milk contains about 1.06 mcg and 100 kcal; 170 g of plain nonfat yogurt contains 1.04 mcg and 95 kcal; one 50 g boiled egg contains 0.56 mcg and 78 kcal. A vegan diet uses B12-fortified foods or supplements, checking the amount on the label. The food table is based on USDA SR28; species and processing may give different values. The amount in food is not the absorbed amount in malabsorption. Fortified drinks, cereals and nutritional yeast depend on the brand: take their B12 content from the label rather than assigning it to the whole category.

Food	Group	Amount	Serving	Calories	Sources
Clamsmixed species, cooked with moist heat	Seafood	98.89 mcg / 100 g	85 g · 84.0565 mcg · 125.8 kcal	148 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Blue musselsraw edible weight	Seafood	12 mcg / 100 g	85 g · 10.2 mcg · 73.1 kcal	86 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Wild Atlantic salmonraw edible weight before cooking	Fish	3.18 mcg / 100 g	150 g · 4.77 mcg · 213 kcal	142 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Pink salmonraw edible weight before cooking	Fish	4.15 mcg / 100 g	150 g · 6.225 mcg · 190.5 kcal	127 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Sockeye salmonraw edible weight before cooking	Fish	4.69 mcg / 100 g	150 g · 7.035000000000001 mcg · 196.5 kcal	131 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Beef liverpan-fried	Organ meats	83.13 mcg / 100 g	50 g · 41.565 mcg · 87.5 kcal	175 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Pork liverbraised	Organ meats	18.67 mcg / 100 g	50 g · 9.335 mcg · 82.5 kcal	165 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Chicken breastraw, skinless and boneless	Meat	0.21 mcg / 100 g	150 g · 0.315 mcg · 180 kcal	120 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Egghard-boiled	Eggs and dairy products	1.11 mcg / 100 g	50 g · 0.555 mcg · 77.5 kcal	155 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Cheddarcheese	Eggs and dairy products	1.1 mcg / 100 g	30 g · 0.33 mcg · 121.2 kcal	404 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
2% milkfluid, with vitamins A and D	Eggs and dairy products	0.53 mcg / 100 g	200 g · 1.06 mcg · 100 kcal	50 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Plain nonfat yogurtno additions	Eggs and dairy products	0.61 mcg / 100 g	170 g · 1.037 mcg · 95.2 kcal	56 kcal / 100 g	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗

Amount comparison

Choose a food target

Fewer calories among portions of a suitable size: Clams — 3 g, about 4 kcal; Beef liver — 3 g, about 5 kcal; Blue mussels — 20 g, about 17 kcal.

A reference for total intake from all sources; this is not a supplement dose for a specific effect. The top list is calculated from the verified set using up to 2.5 of the listed servings. Vitamin B12 — Health Professional Fact Sheet (NIH ODS) ↗

Food	Substance and kcal per 100 g	Adults aged 19 and over: 2.4 mcg	Pregnancy: 2.6 mcg	Breastfeeding: 2.8 mcg	Source
Clamsmixed species, cooked with moist heatSeafood	98.89 mcg148 kcal	3 g≈4 kcal	3 g≈4 kcal	3 g≈4 kcal	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Beef liverpan-friedOrgan meats	83.13 mcg175 kcal	3 g≈5 kcal	4 g≈7 kcal	4 g≈7 kcal	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Blue musselsraw edible weightSeafood	12 mcg86 kcal	20 g≈17 kcal	22 g≈19 kcal	24 g≈21 kcal	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Pork liverbraisedOrgan meats	18.67 mcg165 kcal	13 g≈21 kcal	14 g≈23 kcal	15 g≈25 kcal	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Sockeye salmonraw edible weight before cookingFish	4.69 mcg131 kcal	52 g≈68 kcal	56 g≈73 kcal	60 g≈79 kcal	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Pink salmonraw edible weight before cookingFish	4.15 mcg127 kcal	58 g≈74 kcal	63 g≈80 kcal	68 g≈86 kcal	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Wild Atlantic salmonraw edible weight before cookingFish	3.18 mcg142 kcal	76 g≈108 kcal	82 g≈116 kcal	89 g≈126 kcal	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Plain nonfat yogurtno additionsEggs and dairy products	0.61 mcg56 kcal	394 g≈221 kcal	427 g≈239 kcal · large amount	460 g≈258 kcal · large amount	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
2% milkfluid, with vitamins A and DEggs and dairy products	0.53 mcg50 kcal	453 g≈227 kcal	491 g≈246 kcal	529 g≈265 kcal · large amount	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Egghard-boiledEggs and dairy products	1.11 mcg155 kcal	217 g≈336 kcal · large amount	235 g≈364 kcal · large amount	253 g≈392 kcal · large amount	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
CheddarcheeseEggs and dairy products	1.1 mcg404 kcal	219 g≈885 kcal · large amount	237 g≈957 kcal · large amount	255 g≈1,030 kcal · large amount	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗
Chicken breastraw, skinless and bonelessMeat	0.21 mcg120 kcal	1,143 g≈1,372 kcal · large amount	1,239 g≈1,487 kcal · large amount	1,334 g≈1,601 kcal · large amount	USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗

USDA National Nutrient Database for Standard Reference, Release 28 (SR28): ASCII data and documentation ↗

Studies

Publication	What was studied	Participants	Form and dose	Result
Short-Term Methylcobalamin Supplementation Is Associated with Changes in Anaerobic and Cognitive Performance in Amateur Cyclists: A Randomized Crossover Trial ↗	Power in a short cycling sprint	18 male recreational cyclists; all completed both periods	Sublingual methylcobalamin: 1 mg/day. Three days on each regimen; seven days between periods	Peak power in a Wingate series: 764.1 versus 734.2 W, about +30 W or +4.1%. This is a short high-intensity test, not prolonged endurance.
Effect of two different sublingual dosages of vitamin B(12) on cobalamin nutritional status in vegans and vegetarians with a marginal deficiency: A randomized controlled trial ↗	B12 intake on a plant-based diet	40 vegans and vegetarians with borderline B12 levels	Sublingual vitamin B12: 50 mcg daily or 2000 mcg once weekly. 12 weeks	B12 status markers improved with both regimens. There was no placebo without B12; equal clinical effectiveness of the regimens was not established. Changes in tests do not imply increased energy with adequate B12.
Lack of association between serum vitamin B12 and nocturnal sleep parameters following cyanocobalamin supplementation in healthy adults ↗	Usual sleep	14 adults with baseline B12 above the authors' deficiency threshold; one participant lacked final-week data	Oral cyanocobalamin: 3 mg/day. 14 days	Actigraphy found no significant changes in sleep duration, sleep onset time or sleep efficiency relative to the pre-supplement period. There was no placebo.

Vitamin B12

Main conclusion

Potential benefits

What was studied

How to obtain it from food

Effects and studied questions

Guidance for each goal

Power in a short cycling sprint

B12 intake on a plant-based diet

Usual sleep

Safety and limitations

Forms

Food sources

Studies

Sources