Methylcobalamin (active vitamin B12)
Methylcobalamin is the bioactive coenzyme form of vitamin B12 used in the cytoplasm for methionine synthase — the enzyme that recycles homocysteine to methionine in the methylation cycle. It is often marketed as the form that needs no conversion, but supplemental methylcobalamin undergoes the same intracellular processing as cyanocobalamin and, on current evidence, is unlikely to be advantageous over it. It is one of two bioactive coenzyme forms (the other is adenosylcobalamin, used in mitochondria); both are produced from dietary B12 in healthy adults with intact intrinsic-factor absorption. Vitamin B12 (the molecule) carries multiple authorised UK food-supplement health claims at ≥0.375 µg per serving — Camden NB-551 supplies 1000 µg.
Camden Medicals editorial · Last reviewed 11 June 2026 · Next review June 2027
- Cross-checked against
- NHS
- NICE
- BNF
- EFSA
- FSA
Camden's editorial team independently graded each health claim below on the strength of the published evidence — see the grade beside every condition.
- Class
- Vitamin
- NHS daily RNI
- 2.5 µg
- Typical supplemental
- UK retail B12 supplements typically supply 250–2000 µg per serving — far above NRV — to accommodate the modest oral absorption ceiling at any single dose. Camden NB-551 supplies 1000 µg (1 mg) per capsule, daily.
- Top use evidence
- Strong
On this page
What it is
Methylcobalamin is one of the bioactive coenzyme forms of vitamin B12 (cobalamin). The cobalt at the centre of the corrin ring carries a methyl group as its upper ligand, which methionine synthase transfers to homocysteine in the cytoplasm to produce methionine — the precursor to S-adenosylmethionine (SAMe), the universal methyl donor for ~200 methylation reactions across DNA, histones, neuro- transmitters, and phospholipids. The other bioactive form is adenosylcobalamin, used in mitochondria for the methylmalonyl-CoA mutase reaction in branched-chain amino-acid and odd-chain fatty- acid metabolism. Both forms are produced inside cells from dietary cobalamin (whatever the form supplemented).
Commercial vitamin B12 supplements arrive in four main forms. Cyanocobalamin is the cheapest and most common — a synthetic form with a cyanide group on the cobalt centre that the body removes and excretes during conversion to the active forms. Hydroxocobalamin is the form used in NHS intramuscular injections for diagnosed B12 deficiency (UK BNF: 1 mg every 2–3 months for maintenance once repleted). Methylcobalamin and adenosylcobalamin are the two bioactive coenzyme forms supplied directly. For oral supplementation in healthy adults, the body's conversion of cyanocobalamin to active forms is efficient and the form difference is small. The case for paying for methylcobalamin specifically rests on (a) consumer preference to avoid the cyanide moiety, (b) the marketing-pharma- cokinetic claim that the bioactive form is delivered intact (some pharmacokinetic data supports modestly different tissue distribution), and (c) the MTHFR-variant context, where the methylation cycle's efficiency may be reduced and the bioactive form may be preferred.
Camden NB-551 supplies 1000 µg (1 mg) of methylcobalamin per capsule in an HPMC vegan capsule. This is 40,000% of the UK NRV (2.5 µg) — a deliberately high dose that allows consumer self-titration and accommodates the modest oral B12 absorption ceiling at any single dose (passive paracellular absorption begins above the intrinsic- factor saturation point at ~1.5–2.5 µg per dose, and adds roughly 1% of the supplemented dose into circulation).
Regulatory note: methylcobalamin is a lawful UK food supplement. Vitamin B12 (the molecule) carries multiple authorised UK food- supplement health claims at ≥0.375 µg per serving (≥15% NRV); the claims attach to the vitamin, not specifically to the methyl form. Authorised claims include normal energy-yielding metabolism, normal red blood cell formation, normal nervous-system function, normal homocysteine metabolism, normal psychological function, normal immune function, reduction of tiredness and fatigue, and a role in cell division.
At a glance
- A bioactive coenzyme form of vitamin B12 — used by cytoplasmic methionine synthase in the methylation cycle. Often marketed as needing "no conversion", but supplemental methylcobalamin is processed intracellularly like other forms and is not shown to be superior to cyanocobalamin.
- Vitamin B12 (the molecule) carries authorised UK food-supplement health claims at ≥0.375 µg per serving (≥15% NRV 2.5 µg) — contributes to normal energy-yielding metabolism, normal red blood cell formation, normal nervous-system function, normal homocysteine metabolism, normal psychological function, normal immune function, and reduction of tiredness and fatigue.
- Form-split with cyanocobalamin (synthetic, cheap, requires conversion), adenosylcobalamin (active, mitochondrial), and hydroxocobalamin (used in NHS injections). The body converts cyanocobalamin to methyl- and adenosyl- readily in healthy adults — the form difference is small for general supplementation.
- Pernicious anaemia is a hospital-led diagnosis with NHS hydroxocobalamin injection — NOT an OTC methylcobalamin self-treatment pathway. Suspected B12 deficiency: see your GP.
- Plant-based diets are the highest-prevalence UK B12-deficiency context. Standard food-supplement framing for vegans + vegetarians is well-supported; methylcobalamin is frequently the chosen form because it skips the cyanide moiety some consumers prefer to avoid.
- MTHFR genetic variants (~30–40% of UK adults carry one or more) reduce methylation-cycle efficiency; methylcobalamin alongside methylfolate is the bioactive-form pairing some consumers prefer for this context.
What people use it for
Adults on plant-based diets (vegan, vegetarian, fish-only) seeking to avoid B12 deficiency
Plant-based diets are the highest-prevalence UK context for B12 deficiency, because B12 is essentially absent from plants. The NHS and the British Dietetic Association both advise vegans to take a B12 supplement (or rely on fortified foods). Vitamin B12 carries authorised UK food-supplement claims: it contributes to normal energy-yielding metabolism, normal red blood cell formation, normal functioning of the nervous system, and the reduction of tiredness and fatigue. Methylcobalamin and cyanocobalamin both deliver the vitamin. [1]
StrongAdults aged 60+ at risk of food-cobalamin malabsorption
Atrophic gastritis (reduced stomach acid and reduced intrinsic factor) becomes more common with age and reduces absorption of food-bound B12, which needs stomach acid to be released before it binds intrinsic factor. The free crystalline B12 in a supplement is not bound to food, so it is less affected by this. NICE Clinical Knowledge Summaries describe how a GP investigates suspected deficiency; clinical investigation is appropriate when symptoms are present rather than self-diagnosis. [4]
Some evidenceStrongAdults with confirmed pernicious anaemia or post-gastrectomy B12 malabsorption
Pernicious anaemia is sometimes self-treated with high-dose oral methylcobalamin, but this is not the NHS pathway. Suspected pernicious anaemia is investigated by a GP (intrinsic-factor antibody testing, full blood count, and serum B12 / MMA / homocysteine assessment), and the NHS manages confirmed deficiency with hydroxocobalamin injection. Replacing that pathway with an over-the-counter supplement can mask the diagnosis; talk to your GP. [2]
Not supportedStrongAdults with MTHFR C677T or A1298C variants seeking bioactive-form supplementation
The bioactive-form pairing of methylcobalamin with methylfolate (5-MTHF) is widely discussed online for the MTHFR-variant context. The current evidence does not establish a clinical benefit over standard forms for healthy adults. Reduced enzyme activity can raise plasma homocysteine in variant carriers, which is the rationale offered for the bioactive forms, but the UK NHS does not routinely test or manage MTHFR variants outside specific clinical contexts.
Popular, not provenLimited
How it works
Methylcobalamin enters the cytoplasm and acts as the cofactor for methionine synthase (MTR), which transfers a methyl group from 5-methyltetrahydrofolate (active folate) to homocysteine to produce methionine. Methionine is then activated to S-adenosylmethionine (SAMe), the universal methyl donor. After donating its methyl group, SAMe becomes S-adenosylhomocysteine (SAH), then homocysteine, closing the methylation cycle. The cycle thus depends on three nutrient cofactors simultaneously: B12 (methylcobalamin), folate (5-MTHF), and B6 (pyridoxal-5-phosphate, for the parallel transsulfuration pathway).
The MTHFR gene encodes methylenetetrahydrofolate reductase, the enzyme that produces 5-MTHF from 5,10-methylene-THF. Reduced- function variants (C677T homozygotes have ~70% reduced activity; heterozygotes ~30–40%) lower the cycle's throughput, raise plasma homocysteine, and rationalise the bioactive-form supplementation case (methylcobalamin + methylfolate, bypassing both the cyanocobalamin conversion step and the MTHFR step).
Adenosylcobalamin's mitochondrial role is in the methylmalonyl-CoA mutase reaction that converts methylmalonyl-CoA to succinyl-CoA in the catabolism of valine, isoleucine, methionine, threonine, odd- chain fatty acids, and cholesterol. Methylmalonic acid (MMA) accumulation is a sensitive marker of cellular B12 deficiency.
Common myths
Myth"Methylcobalamin is dramatically more bioavailable than cyanocobalamin"
RealityThe difference is small for most healthy adults. The body converts cyanocobalamin to active forms (methylcobalamin and adenosylcobalamin) readily; the cyanide moiety is excreted. UK NHS injections use hydroxocobalamin specifically because of its longer plasma half-life — not because methylcobalamin would be a "better" choice. The marketing framing of methylcobalamin as fundamentally superior overstates the modest pharmacokinetic differences.
Myth"Methylcobalamin is the only "natural" form of B12"
RealityAll four supplement forms (cyanocobalamin, methylcobalamin, adenosylcobalamin, hydroxocobalamin) are produced via bacterial fermentation. None come from a plant or animal source directly. Hydroxocobalamin is the form most abundant in animal foods (it is also the form the body stores in the liver). Methylcobalamin is the cytoplasmic active form but is not "more natural" — it is more bioactive at the cellular level.
Myth"High-dose B12 has dose-related toxicity"
RealityNo upper-tolerable-intake level has been set for vitamin B12 by the European Food Safety Authority or the UK SACN — water- soluble vitamin, no documented toxicity from supplementation up to several mg/day. The body excretes excess via urine. There is no UK food-supplement upper limit. Camden NB-551 supplies 1 mg per capsule comfortably within this safety margin.
Myth"Methylcobalamin can repair MTHFR genetic variants"
RealityIt cannot. MTHFR variants are gene-level and permanent. Methylcobalamin (alongside methylfolate) supports the methylation cycle by supplying the bioactive cofactors directly, bypassing the reduced-activity MTHFR step. The supplementation rationale is to support cycle throughput, not to repair the gene. UK NHS does not routinely test or manage MTHFR variants outside specific clinical contexts.
Myth"You can self-supplement methylcobalamin to avoid B12 injections for pernicious anaemia"
RealityHigh-dose oral B12 has trial-level evidence for equivalence to intramuscular dosing in some absorption contexts, but this is a clinical decision for your prescriber — not a self-supplement choice. UK NHS standard practice for pernicious anaemia is hydroxocobalamin injection. Self-supplementing in place of prescriber-managed therapy can mask diagnostic markers (serum B12 + MMA + homocysteine) and complicate downstream care. [2]
Common online questions
Synthesised from the questions UK shoppers most often ask online about Methylcobalamin (active vitamin B12). Each answer is editorial and links to its evidence in the Sources list below.
What is the difference between methylcobalamin and cyanocobalamin?
Both are vitamin B12. Cyanocobalamin is the cheap synthetic form with a cyanide group on the cobalt centre — the body removes and excretes the cyanide moiety while converting it to the active coenzyme forms. Methylcobalamin is one of two bioactive coenzyme forms (the other is adenosylcobalamin) — the form your cells actually use for the methylation cycle. For most healthy adults with normal absorption, the body converts cyanocobalamin to active forms readily and the practical difference is small. Methylcobalamin avoids the cyanide moiety, may marginally suit consumers with MTHFR variants, and is the form Camden NB-551 supplies (1000 µg per capsule).
How much vitamin B12 do I need?
UK NRV (Nutrient Reference Value, the food-label reference) is 2.5 µg per day. The UK SACN reference intake is similar. Authorised UK food-supplement health claims kick in at ≥0.375 µg per serving (≥15% NRV). Most B12 supplements supply 250–1000 µg per serving — far above NRV — to accommodate the modest oral absorption ceiling at any single dose. Camden NB-551 supplies 1000 µg per capsule (40,000% NRV). [1]
Can I take methylcobalamin if I have pernicious anaemia?
Talk to your GP. Pernicious anaemia is the autoimmune destruction of the gastric parietal cells that produce intrinsic factor — without intrinsic factor, B12 cannot be absorbed via the normal ileal pathway. UK NHS practice for pernicious anaemia is hydroxocobalamin intramuscular injection (a Prescription-Only Medicine), not oral methylcobalamin self-supplementation. High-dose oral B12 has trial-level evidence for equivalence to intramuscular dosing in some absorption contexts via passive paracellular absorption — but this is a clinical decision for your prescriber, not a self-supplement choice. [2]
Is methylcobalamin "vegan-friendly"?
Yes — both methylcobalamin and cyanocobalamin in supplement form are produced via bacterial fermentation, not animal sourcing. Camden NB-551 uses an HPMC (hydroxypropylmethylcellulose) vegan capsule shell. Plant-based diets are the highest-prevalence UK context for B12 deficiency because B12 is essentially absent from plants — daily supplementation is the standard dietitian guidance for vegans. Vegetarians who eat dairy and eggs typically get adequate B12 from those sources, but supplementation is a reasonable hedge. [1]
Do I need to test for MTHFR variants before choosing methylcobalamin?
No — MTHFR genotype testing is not a UK NHS prerequisite for B12 supplementation. Reduced-function MTHFR variants are common (~30–40% of UK adults carry one or more) but the practical impact on healthy-adult B12 supplementation is small in most cases. Bioactive-form supplementation (methylcobalamin + methylfolate) is a reasonable choice for consumers who prefer the bypass-the-MTHFR-step route on first principles, regardless of genotype testing.
Can I take methylcobalamin with my prescription medication?
Vitamin B12 has very few prescription-medication interactions. Long-term use of metformin (type 2 diabetes), proton-pump inhibitors (omeprazole, lansoprazole, pantoprazole, esomeprazole), H2 blockers (ranitidine, famotidine), and colchicine can reduce B12 absorption — supplementation may be appropriate but is a decision for your GP. Nitrous oxide anaesthesia inactivates circulating B12 and can precipitate deficiency in those with marginal status. Otherwise, B12 supplementation is well- tolerated alongside most prescriptions. [3]
⚖️ The official position
What may lawfully be claimed about Methylcobalamin (active vitamin B12) in Great Britain. This is a regulatory position, not an evidence grade.
A health claim is authorised in Great Britain.
“Vitamin B12 contributes to normal energy-yielding metabolism”
“Vitamin B12 contributes to normal red blood cell formation”
“Vitamin B12 contributes to normal functioning of the nervous system”
“Vitamin B12 contributes to normal homocysteine metabolism”
“Vitamin B12 contributes to normal psychological function”
“Vitamin B12 contributes to the normal function of the immune system”
“Vitamin B12 contributes to the reduction of tiredness and fatigue”
“Vitamin B12 has a role in the process of cell division”
This claim is authorised for use in Great Britain under the GB Nutrition and Health Claims regulation. A product may carry it when it provides at least 15% of the UK NRV per recommended daily portion.
Authorised UK health claims
Verbatim from the GB Nutrition and Health Claims Register (Reg 432/2012 as assimilated in GB). A product can carry these claims when it provides at least 15% of the UK NRV per recommended daily portion.
8 authorised claims — show / hide
- "Vitamin B12 contributes to normal energy-yielding metabolism"
- "Vitamin B12 contributes to normal red blood cell formation"
- "Vitamin B12 contributes to normal functioning of the nervous system"
- "Vitamin B12 contributes to normal homocysteine metabolism"
- "Vitamin B12 contributes to normal psychological function"
- "Vitamin B12 contributes to the normal function of the immune system"
- "Vitamin B12 contributes to the reduction of tiredness and fatigue"
- "Vitamin B12 has a role in the process of cell division"
🔬 Camden’s evidence review
The research Camden reviewed, graded on its strength. This is our own appraisal — it sits beneath the official guidance above, never above it.
Vitamin B12 deficiency (oral repletion in healthy adults with normal absorption)
StrongEvidencestrongUK guidance leads: NICE Clinical Knowledge Summaries and the NHS recognise oral B12 supplementation for dietary deficiency and for maintaining adequate status, and vitamin B12 holds authorised UK claims for normal red blood cell formation and energy-yielding metabolism. Beneath that, the research Camden reviewed: daily oral B12 at 500–2000 µg repletes biochemical markers (serum B12, MMA, homocysteine) in adults with normal absorption, and meta-analyses report that high-dose oral regimens can match intramuscular dosing for repletion outside the pernicious-anaemia setting. The form (methylcobalamin versus cyanocobalamin) makes a small difference here; both deliver the vitamin. [4,3]
Pernicious anaemia (intrinsic-factor deficiency)
StrongEvidencestrongUK guidance leads: the NHS and BNF set the pathway for diagnosed pernicious anaemia as hydroxocobalamin 1 mg by intramuscular injection — initially on alternate days for about two weeks (or until no further improvement), then maintenance every 2–3 months. Oral self-supplementation is not the recognised UK route for this diagnosis. Beneath that, the research Camden reviewed: high-dose oral B12 (1000–2000 µg/day) has trial-level evidence for equivalence to injection in some absorption contexts via passive paracellular uptake — but this remains a prescriber's decision, not a self-supplement substitution. [2]
Diabetic peripheral neuropathy — adjunct
LimitedEvidencelimitedUK guidance leads: NICE NG28 (type 2 diabetes in adults) does not list methylcobalamin in the diabetic-neuropathy pathway, and there is no UK-authorised claim for this use. Beneath that, the research Camden reviewed: trials of methylcobalamin, sometimes combined with alpha-lipoic acid, have reported modest improvements in symptoms and nerve-conduction measures, but the studies are generally small and short. Self-supplementation in place of GP review is not appropriate. [5]
Cardiovascular event prevention via homocysteine lowering
MixedEvidencemixedUK guidance leads: NICE does not list homocysteine lowering as a pathway for cardiovascular risk reduction, and no UK-authorised claim links B12 to cardiovascular outcomes. Beneath that, the research Camden reviewed: the large HOPE-2, NORVIT, and VISP trials found that combined B12 and folate supplementation lowered measured homocysteine by about 2–3 µmol/L on average but did not reduce major cardiovascular event rates over 2–5 years of follow-up. Using B12 specifically for cardiovascular outcomes is not supported.
Cognitive function in older adults (mild cognitive impairment)
LimitedEvidencelimitedUK guidance leads: NICE does not list B-vitamin supplementation as a pathway for mild cognitive impairment or dementia, and there is no UK-authorised claim for this use. Beneath that, the research Camden reviewed: some trials of B-vitamin combinations (B6 + B12 + folate) in adults with mild cognitive impairment and raised homocysteine reported reduced brain atrophy on MRI and modest cognitive effects, apparently strongest in those with elevated baseline homocysteine. The evidence is not yet strong enough to be sure.
Safety
Vitamin B12 in any supplement form is well-tolerated. No upper-tolerable-intake level set; the body excretes excess via urine. Methylcobalamin is suitable for vegan and vegetarian diets. Diagnosed pernicious anaemia or B12 deficiency requires GP investigation and the NHS hydroxocobalamin injection pathway, not OTC self-supplementation.
Talk to your pharmacist or GP first if you:
- You take metformin long-term (type 2 diabetes) — long-term use can reduce B12 absorption; supplementation may be appropriate but is a GP decision.
- You take a proton-pump inhibitor (omeprazole, lansoprazole, pantoprazole, esomeprazole) or H2 blocker long-term — reduced stomach acid reduces B12 absorption.
- You take colchicine — can reduce B12 absorption.
- You have had bariatric surgery, gastrectomy, or ileal resection — absorption is impaired and clinical management is required.
- You are pregnant or breastfeeding — B12 supplementation at standard food-supplement doses is generally suitable; talk to your midwife / GP if you are also taking a prescription multivitamin.
- You have symptoms of B12 deficiency (fatigue, pins and needles, sore tongue, poor balance, memory or mood changes) — see your GP for investigation; self-supplementation can mask the diagnosis.
Common side effects: Generally none at standard food-supplement doses. Acne flare or rosacea-like symptoms occasionally reported with very high-dose B12 in cosmetic-context literature.
Pregnancy and breastfeeding
Pregnancy: methylcobalamin at standard food-supplement doses is generally suitable. UK NHS recommends maternal B12 status be adequate during pregnancy; deficiency risks include neural-tube defects (alongside folate). If you are also taking a prescription multivitamin, talk to your midwife / GP to avoid duplication.
Lactation: methylcobalamin at standard food-supplement doses is generally suitable. Maternal B12 status influences breastmilk B12 — supplementation in vegan / vegetarian breastfeeding mothers is well-supported.
Talk to your GP, midwife, or pharmacist before starting any supplement during pregnancy or breastfeeding.
More clinical detail (for clinicians and informed readers)
Contraindications
- Hereditary Leber's optic neuropathy (LHON) — case reports of accelerated progression with high-dose B12; specialist review required.
- Cobalt allergy — uncommon but documented; ophthalmic + dermatologic case literature.
Drug interactions
- Metformin — long-term use reduces B12 absorption; periodic B12 status monitoring is appropriate.
- Proton-pump inhibitors (omeprazole, lansoprazole, pantoprazole, esomeprazole) — reduced stomach acid reduces food-bound B12 release.
- H2 blockers (ranitidine, famotidine) — reduced stomach acid reduces food-bound B12 release.
- Colchicine — reduces B12 absorption.
- Nitrous oxide (anaesthetic) — inactivates circulating B12 and can precipitate deficiency in those with marginal status; pre-anaesthetic screening is prudent in long-term vegans.
- Aminoglycoside antibiotics (neomycin) — can reduce B12 absorption in long-term use.
This is not an exhaustive list. Always tell your prescriber and pharmacist about every supplement you take.
Common side effects
- Generally none at standard food-supplement doses (250–2000 µg/day).
Rare side effects
- Acne flare or rosacea-like symptoms — case reports with very high-dose oral B12 (typically >2 mg/day for prolonged periods).
- Hypersensitivity / allergic reactions — uncommon; more often associated with the cobalt centre than the form-specific moiety.
How to take it
- UK Reference Nutrient Intake
- 2.5 µg/day
- Typical supplemental range
- UK retail B12 supplements typically supply 250–2000 µg per serving — far above NRV — to accommodate the modest oral absorption ceiling at any single dose. Camden NB-551 supplies 1000 µg (1 mg) per capsule, daily.
- Timing
- Any time of day, with or without food. Some consumers prefer morning dosing because of the energy-metabolism authorised claim framing.
How to spot quality
Look for
- Form named explicitly on the label — methylcobalamin, not just "vitamin B12".
- Dose declared in micrograms (µg) per serving and as % NRV (2.5 µg = 100% NRV).
- Vegan-suitability declared (HPMC capsule preferred over gelatin for plant-based consumers).
- GMP-certified manufacture; reputable supplier chain.
- CoA available on request; methylcobalamin assay confirms identity (cobalt content + HPLC chromatogram).
- Excipient list disclosed — pull-up of stearates, titanium dioxide flagged on the label.
- Batch number + expiry date legible on the pack.
Red flags
- Form not declared — "vitamin B12" without specifying cyanocobalamin / methylcobalamin / hydroxocobalamin / adenosylcobalamin.
- Marketing that frames methylcobalamin as fundamentally superior to other forms without quoting the modest pharmacokinetic differences.
- Health claims beyond the GB NHC Register authorised list — e.g. lifespan-extension language, "cognitive enhancement", "MTHFR repair".
- Pernicious-anaemia self-treatment claims — those require GP investigation and NHS hydroxocobalamin injection.
- Doses above 5 mg per serving with no rationale (passive absorption ceiling means higher doses do not buy more delivery).
- No batch number, no expiry date, opaque sourcing.
Where Camden lands · meets the bar
Camden has one methylcobalamin SKU — NB-551 Vitamin B12 Methylcobalamin 1 mg 120 Capsules. The SKU supplies 1000 µg (1 mg, 40,000% NRV) of methylcobalamin per HPMC vegan capsule. Form is declared explicitly on the label. Dose is declared in µg and as % NRV. PDP carries the authorised UK food-supplement claims for B12 (energy metabolism, red blood cell formation, nervous-system function, homocysteine metabolism, psychological function, immune function, reduction of tiredness and fatigue, cell division). NB-551 is currently Wave-1 ready (draft pending reshoot photography); brand assignment is Purifera (single clean active in capsule, not a branded licensed ingredient).
Commonly combined with
Other ingredients that share a biological pathway, cofactor relationship, or evidence-backed protocol with this one. Mechanisms below cite primary physiology — not folk pairing. Doses are literature ranges, not recommendations. Talk to your pharmacist or GP before changing your stack, especially if you take prescription medication.
Methyl Folate (5-Methyltetrahydrofolate)
Moderate evidenceBioactive-form pair — methylcobalamin (B12) and methylfolate (5-MTHF) cooperate at methionine synthase to recycle homocysteine to methionine. Combining them is the canonical bioactive-form supplementation pattern, especially in the MTHFR-variant context. UK food-supplement co-claim is not authorised; individual claims for each vitamin apply at threshold doses.
Methionine synthase transfers a methyl group from 5-MTHF (folate) to homocysteine via the methylcobalamin (B12) cofactor, producing methionine and tetrahydrofolate. Both cofactors must be present for the reaction. Bioactive-form supplementation supplies them directly, bypassing both the cyanocobalamin conversion step and the MTHFR enzyme step. In MTHFR variant carriers (~30–40% of UK adults) the 5-MTHF supply is reduced; methylfolate supplementation bypasses the constraint.
Evidence: Multiple trials confirm the combination lowers measured plasma homocysteine more than either alone. Clinical-outcome trials (cardiovascular events, cognition) are mixed; biochemical-marker improvement is well-supported. [7,8,9]
Doses studied: Methylcobalamin 500–1000 µg + methylfolate 400–600 µg per serving. Camden NB-548 supplies the methylfolate side (Quatrefolic® 600 µg); NB-551 supplies the methylcobalamin side (1000 µg).
Found in Camden: Aurifera™ Methyl Folate Quatrefolic® 600µg 90 Capsules · Purifera™ Vitamin B12 Methylcobalamin 1mg 120 Capsules
Vitamin B6
Moderate evidenceMethylation-cycle triad — B12 + folate + B6 are the three cofactors that keep plasma homocysteine within reference range. B6 supports the parallel transsulfuration pathway via cystathionine beta-synthase. UK food-supplement co-claim is not authorised; individual claims apply at threshold doses.
Vitamin B12 is the cofactor for methionine synthase, which converts homocysteine back to methionine using a methyl group donated by 5-MTHF. Vitamin B6 (pyridoxal-5-phosphate) is the cofactor for the parallel transsulfuration pathway, where cystathionine beta- synthase converts homocysteine to cystathionine, the precursor of cysteine and glutathione. Adequate status in both vitamins keeps plasma homocysteine within reference range; deficiency in either raises it. The HOPE-2, NORVIT, and VISP trials confirmed that combined supplementation lowers measured homocysteine by 2–3 µmol/L on average, but did not reduce major cardiovascular event rates over 2–5 years follow-up.
Evidence: Biochemical-marker improvement is well-supported. Clinical-outcome trials for cardiovascular endpoints are mixed; UK NICE does not list homocysteine lowering as a CV-risk pathway. [10,11]
Doses studied: B-complex supplements typically supply B12 25–500 µg + folate 200–400 µg + B6 5–25 mg per serving.
Vitamin B12
Insufficient evidenceParent / form-split sibling — vitamin-b12 is the molecule-level entry; methylcobalamin is the bioactive-form sibling. Both entries cite each other; the form-comparison table lives on the parent.
All vitamin B12 supplement forms (cyanocobalamin, methylcobalamin, adenosylcobalamin, hydroxocobalamin) deliver the same vitamin. The body converts cyanocobalamin to active forms readily; methylcobalamin and adenosylcobalamin are supplied directly as bioactive coenzyme forms; hydroxocobalamin is the form most abundant in animal foods and used in NHS injections for pernicious anaemia.
Evidence: Pharmacokinetic differences are modest in healthy adults with normal absorption.
Doses studied: Not a typical co-supplementation pattern (one form per supplement).
Found in Camden: Purifera™ Vitamin B12 Methylcobalamin 1mg 120 Capsules