Products / Supplement
Methylcobalamin (Vitamin B12)
Methylcobalamin is the active, methylated form of Vitamin B12, used directly in cellular metabolism without the conversion step required for cyanocobalamin. Suited to patients with low B12, low folate-related markers, or raised homocysteine identified on a blood test.
Suitability and pricing are confirmed with your clinician at review.
About this product
Vitamin B12 supplementation is most commonly sold as cyanocobalamin (the synthetic form) which the body must convert to the active methylcobalamin or adenosylcobalamin forms. We range methylcobalamin directly so the supplement does not require conversion before use as a methylation co-factor. NICE NG239 (March 2024) defines confirmed B12 deficiency as a total serum B12 below 180 ng/L (133 pmol/L), with 180 to 350 ng/L treated as indeterminate. Oral B12 is recognised by NG239 as an option for dietary deficiency and some medicine-induced cases; intramuscular B12 replacement (hydroxocobalamin in UK practice per the BNF) is offered for malabsorption causes such as autoimmune gastritis. This product is particularly useful in patients with raised methylmalonic acid or homocysteine, in vegan and vegetarian diets, and in older adults where gastric atrophy reduces B12 absorption. Important testing note: oral B12 raises serum B12 levels, so if a repeat blood test is planned, oral methylcobalamin is usually paused for several weeks beforehand to avoid a falsely normal result. NICE NG239 does not specify a fixed wash-out period but advises clinicians to ask about supplement use and interpret results with caution; private-medicine practice typically uses around four weeks. After an intramuscular hydroxocobalamin injection, serum B12 stays elevated for weeks to months (UK SmPCs support a 2 to 3 month gap between maintenance doses), so the timing of any repeat test should be agreed with your prescriber. Folate status should also be checked alongside B12, since correcting B12 deficiency without addressing low folate (or vice versa) can mask or worsen the underlying picture.
How it works
Methylcobalamin is the methylated form of Vitamin B12 that the body uses directly as a co-factor in methionine synthase, the enzyme that converts homocysteine to methionine. Without adequate B12, homocysteine accumulates and methylation reactions across the body are impaired. Symptoms of B12 deficiency include fatigue, paraesthesia, memory and concentration changes, and macrocytic anaemia.
Who this product is for
- Your blood test has shown low B12, raised methylmalonic acid, or raised homocysteine
- You follow a vegan or vegetarian diet
- You are over 50 (B12 absorption declines with age)
- You take medications that reduce B12 absorption (metformin, long-term PPIs)
Active ingredients
- · Methylcobalamin (active form of Vitamin B12)
Linked blood markers
This supplement is most useful when paired with a blood test result. Read the clinical context for each linked marker on WMG Healthcare:
Important information
This supplement is not a prescription medication and is sold for general health use under clinician guidance. It is not a substitute for diagnosis or treatment. If you have a chronic medical condition, take prescribed medications, are pregnant or breastfeeding, or are under 18, speak to a clinician before starting a new supplement.
If you experience side effects or have any clinical concerns, contact us via the enquiry form or call 020 3239 3378. For urgent symptoms please contact your GP, NHS 111, or 999.
Other supplements
Compare against the rest of the range.