Vitamin B12 (Adenosylcobalamin)

Mitochondrial coenzyme form of B12 essential for energy metabolism and cellular respiration

Scientific nameAdenosylcobalamin FormulaC72H100CoN18O17P Molecular weight1579.58 g/mol CAS13870-90-1

80 absorption score

10 safety / 10

60 USD per month

5 documented interactions

Check it against something

Evidence level A

Vitamin B12 (Adenosylcobalamin) with:

87 out of 100

Works better together Compatible. Timing differs, so follow each supplement's own window.

Check it against your whole stack →

What it does

mechanism and evidence for each claim

Enhanced energy metabolism

Essential coenzyme for mitochondrial energy production

Required for methylmalonyl-CoA mutase enzyme Evidence A-grade 1-3 weeks

Mitochondrial support

Optimizes cellular powerhouse function

Critical for fatty acid oxidation in mitochondria Evidence A-grade 2-4 weeks

Metabolic efficiency

Improves conversion of nutrients to energy

Essential for branched-chain amino acid metabolism Evidence A-grade 2-6 weeks

Complementary B12 action

Works synergistically with methylcobalamin

Covers mitochondrial functions that methylB12 doesn't Evidence B-grade 3-8 weeks

Athletic performance support

May enhance exercise capacity and recovery

Optimized cellular energy production pathways Evidence C-grade 4-8 weeks

Others take these for the same thing

Same goal, different mechanism — check any of them against this one

Ashwagandha Stress management & energy 300-600mg A 75% Vitamin B12 (Cyanocobalamin) Energy & nerve support 250-1000 mcg A 70% Coenzyme Q10 (CoQ10) Heart health & cellular energy 100-200mg A 10% Phosphorus Bone health & energy metabolism 700-1250mg A 80% Vitamin B3 (Niacinamide) Energy & skin health (no flush) 100-1000 mg A 88% Berberine for Advanced Glucose Control and Metabolic Support Blood sugar control & metabolic support 1500mg daily (500mg x3) A 60%

Or a different form of the same thing

the comparison people search most

Vitamin B12 (Adenosylcobalamin) vs Vitamin B12 (Cyanocobalamin) absorption 80 against 70 · $60 against $8 a month 70% Vitamin B12 (Adenosylcobalamin) vs Vitamin B12 (Methylcobalamin) absorption 80 against 85 · $60 against $15 a month 85% Vitamin B12 (Adenosylcobalamin) vs Vitamin B12 (Hydroxocobalamin) absorption 80 against 75 · $60 against $35 a month 75%

All Vitamin B12 forms ranked by absorption →

Every pair we checked

12 combinations scored by the engine

Vitamin B12 (Adenosylcobalamin) + Caffeine No documented interaction either way No known interaction 70

Vitamin B12 (Adenosylcobalamin) + Creatine Monohydrate No documented interaction either way No known interaction 70

Vitamin B12 (Adenosylcobalamin) + Whey Protein No documented interaction either way No known interaction 70

Vitamin B12 (Adenosylcobalamin) + Turmeric No documented interaction either way No known interaction 70

Vitamin B12 (Adenosylcobalamin) + Vitamin D3 Prevents arterial calcification from vitamin D Works better together 78

Vitamin B12 (Adenosylcobalamin) + Lactase Improved calcium absorption when consuming dairy Works better together 82

Vitamin B12 (Adenosylcobalamin) + Bovine Collagen Essential for collagen synthesis and cross-linking Works better together 82

Vitamin B12 (Adenosylcobalamin) + DHA Prevents oxidation of DHA and enhances stability Works better together 82

Vitamin B12 (Adenosylcobalamin) + Coenzyme Q10 (CoQ10) Both support mitochondrial energy production Works better together 87

Vitamin B12 (Adenosylcobalamin) + Vitamin B12 (Methylcobalamin) Complementary B12 functions for complete support Works better together 90

Vitamin B12 (Adenosylcobalamin) + Magnesium Oxide Required for many mitochondrial enzymes Works better together 90

Vitamin B12 (Adenosylcobalamin) + Calcium Carbonate Essential for calcium absorption and utilization Works better together 94

Dosage

Morning with food

Daily1000-3000 mcg

Maintenance500-1000 mcg

Therapeutic2000-5000 mcg

MaximumNo established upper limit

CombinationOften used with 500-1000 mcg methylcobalamin

Before you take it

VeganYes

When to expect it

First Effects1-3 weeks for energy improvements

Peak Benefits6-12 weeks for metabolic optimization

Deficiency Development3-5 years with no B12 intake

Toxicity OnsetNo known toxicity at any dose

How to measure it

$80-120

MarkerMethylmalonic acid (MMA) - specific for adenosyl function

OptimalMMA: <0.4 μmol/L

FrequencyEvery 6-12 months if using for energy/mitochondrial support

What people actually reported to the FDA

CAERS, 61 reports naming it as the suspect

Most reported effects

Malaise 9

Nausea 7

Pruritus 6

Urticaria 6

Dizziness 6

Named as the suspect 61 reports of 641 that mention it at all

Serious outcome 80% hospitalisation, emergency room or worse

Other Serious or Important Medical Event40

Hospitalization13

Visited Emergency Room11

Reports are voluntary and unverified — they record what someone experienced while taking something, not what the compound caused. Counts skew towards products people take a lot of, and a serious outcome is more likely to be reported than a mild one, so these are not rates. How we filter them →

What actually reaches you

The label counts the carrier, your body does not

Absorption Very high 80 of 100 · best absorbed form of this compound

Delivered daily 1.6 mg

Cost per 10 mg delivered $12.50 comparative — uses the absorption score, not a measured percentage

Works better with

3 documented

Methylcobalamin

Complementary B12 functions for complete support

Covers different B12-dependent pathways · level B

Coq10

Both support mitochondrial energy production

Complementary roles in cellular respiration · level C

Magnesium

Required for many mitochondrial enzymes

Cofactor for energy metabolism enzymes · level B

What not to take with Vitamin B12 (Adenosylcobalamin)

2 documented

Nitrous Oxide

Inactivates all forms of B12 including adenosyl

Oxidizes cobalt center making B12 inactive · major significance

Alcohol Chronic

Depletes B12 stores and impairs mitochondrial function

Interferes with B12 metabolism and energy production · moderate significance

Medication interactions

Discuss these with a pharmacist before combining

metformin Moderate

Reduces B12 absorption

What to do: Consider adenosylcobalamin supplementation

proton-pump-inhibitors Moderate

Reduces B12 absorption from food

What to do: Adenosylcobalamin supplementation bypasses food absorption

Available forms

bioavailability compared

Ranks 2 of 4 among vitamin b12 forms. Vitamin B12 (Methylcobalamin) absorbs better — 85%. Compare all forms →

Adenosylcobalamin 80

Adenosylcobalamin: Mitochondrial specific, Active form, Energy focused, Complements methylB12

Food sources

before you supplement

Adenosylcobalamin found in small amounts in animal products Primarily available as supplement · 80

Too little

deficiency signs

Metabolic dysfunction symptoms:
Severe fatigue and energy depletion
Exercise intolerance
Poor recovery from physical stress
Plus general B12 deficiency symptoms:
Neurological problems, anemia

Too much

toxicity signs

No known toxicity symptoms
Water-soluble, excess excreted
No upper limit established
Same safety profile as other B12 forms
No reported adverse effects

Who benefits most

chronic-fatigue-sufferers

Mitochondrial B12 may address energy production issues

1000-3000 mcg daily

athletes-endurance

Enhanced mitochondrial function for energy demands

1000-5000 mcg daily

mitochondrial-dysfunction

Specific form needed for mitochondrial enzyme function

2000-5000 mcg daily

methylcobalamin-users

Complements methylB12 for complete B12 functions

500-2000 mcg daily

optimization-seekers

Want complete B12 support regardless of cost

1000-3000 mcg daily

Where to buy it

compare forms first

Look for Vitamin B12 (Adenosylcobalamin) at 1000-3000 mcg per serving. The form that matters here is Adenosylcobalamin.

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What else affects it

Beyond other supplements

Alcohol chronic

Depletes B12 stores and impairs mitochondrial function

Interferes with B12 metabolism and energy production

How it works

Essential cofactor for methylmalonyl-CoA mutase
Required for fatty acid beta-oxidation in mitochondria
Critical for branched-chain amino acid catabolism
Supports mitochondrial energy production pathways
Cannot be replaced by other B12 forms for these functions
Maintains mitochondrial membrane integrity

Key findings

what the evidence supports

Essential for mitochondrial fatty acid oxidation (established biochemistry)
Cannot be replaced by other B12 forms for mitochondrial functions
May be particularly important for energy metabolism disorders
Limited clinical research compared to other B12 forms

Sources: NIH Examine.com · data reviewed 2026-08-02

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of Vitamin B12 (Adenosylcobalamin)?

Documented effects: Enhanced energy metabolism; Mitochondrial support; Metabolic efficiency; Complementary B12 action. Essential coenzyme for mitochondrial energy production

How much Vitamin B12 (Adenosylcobalamin) should you take per day?

The common daily range is 1000-3000 mcg. By goal — maintenance: 500-1000 mcg; therapeutic: 2000-5000 mcg; maximum: No established upper limit; combination: Often used with 500-1000 mcg methylcobalamin.

When is the best time to take Vitamin B12 (Adenosylcobalamin)?

Morning with food. First effects are typically reported within 1-3 weeks for energy improvements.

What are the side effects of Vitamin B12 (Adenosylcobalamin)?

At excessive doses: No known toxicity symptoms, Water-soluble, excess excreted, No upper limit established, Same safety profile as other B12 forms, No reported adverse effects. Safety rating at normal doses is 10 out of 10.

What should you not take with Vitamin B12 (Adenosylcobalamin)?

Separate it from Nitrous Oxide, Alcohol Chronic by two to four hours. Inactivates all forms of B12 including adenosyl

Does Vitamin B12 (Adenosylcobalamin) interact with medications?

Documented interactions with metformin, proton-pump-inhibitors. Discuss these with a pharmacist before combining.

How do you know if you need Vitamin B12 (Adenosylcobalamin)?

The marker is Methylmalonic acid (MMA) - specific for adenosyl function, optimal range MMA: <0.4 μmol/L. Common deficiency signs: Metabolic dysfunction symptoms:, Severe fatigue and energy depletion, Exercise intolerance, Poor recovery from physical stress.

Taken for

62 Energy & Metabolism

Vitamin B12 (Methylcobalamin) · Ashwagandha · Vitamin B12 (Cyanocobalamin)