--- title: "Methylcobalamin vs cyanocobalamin: which B12 should you take?" url: https://nutritailor.co.uk/apps/learn/methylcobalamin-vs-cyanocobalamin-which-b12-should-you-take slug: methylcobalamin-vs-cyanocobalamin-which-b12-should-you-take pillar: B Vitamins publisher: "Nutri Tailor Health Reference Library" editor: "Henry Bond" publisher_makes: "Nutri365, the only UK app that combines your Oura data, blood test results and what you tell it into personalised guidance" --- # Methylcobalamin vs cyanocobalamin: which B12 should you take? ## Summary Both raise B12 levels and both are accepted in the UK guideline, so neither is the wrong choice. Cyanocobalamin is the standard form: the most stable, the cheapest, and the one used in almost all the trials, including the Cochrane review that found oral B12 as effective as injections for most people. The body removes the tiny cyanide group and converts it to the two active forms. Methylcobalamin is one of those active forms, so it skips a step, but the 2017 review found no evidence that this makes it work better. Pick methylcobalamin if you prefer an active form in a capsule; pick cyanocobalamin for the most studied form at the lowest cost. ## How it works B12 is absorbed two ways. A small amount binds to intrinsic factor in the stomach and is taken up in the last part of the small intestine; that route saturates at a few micrograms. About one percent of any oral dose is absorbed by simple diffusion regardless of intrinsic factor, which is why very high oral doses of 1000 mcg or more work even when the first route has failed. Both forms use both routes. The cyanide in cyanocobalamin is about 20 micrograms per 1000 mcg dose, far below what a portion of almonds contains, and is cleared in urine. ## Effective dose The UK reference intake is 1.5 mcg a day, easily met from animal foods. For a confirmed deficiency, NICE NG239 (2024) accepts oral B12 as an alternative to injections when the cause is dietary or when the person prefers it, at doses the GP sets; the trials used 1000 to 2000 mcg a day. For people on plant based diets, 10 mcg a day or 2000 mcg once a week are the commonly used maintenance figures. Both forms are available at these doses. ## Forms compared Vitamin B12 comes in four supplement forms. Cyanocobalamin is the manufactured standard, stable in a bottle for years. Methylcobalamin and adenosylcobalamin are the two forms the body actually uses, one in the methylation cycle and one in the mitochondria. Hydroxocobalamin is the natural form in food and the form used in UK injections. Whichever form you swallow, the cell removes the attached group and rebuilds the form it needs, so a methylcobalamin supplement does not stay methylcobalamin, and a cyanocobalamin supplement does not stay cyanocobalamin. That is why the guideline regards them as interchangeable for correcting a deficiency. ## Timing Any time of day, with or without food. Drops held under the tongue for a minute before swallowing are pleasant to take, though the evidence for extra absorption through the mouth is weak; the swallowed dose still works. Retest after eight weeks if you are correcting a low result. ## Safety profile B12 has no upper limit in the UK because excess is passed in urine. Very high oral doses occasionally cause acne like spots, which settle when the dose drops. The important safety point is not the form but the cause: a low B12 with no dietary explanation needs a GP to check for pernicious anaemia or absorption problems before a supplement is chosen. ## Guideline positions NICE NG239 (2024): vitamin B12 deficiency in over 16s, diagnosis and management, which allows oral replacement for suitable people and does not favour one oral form. Cochrane review (2018): oral versus intramuscular B12 for deficiency. Methylcobalamin in vitamin B12 deficiency: to give or not to give (2017). NICE CKS: anaemia, B12 and folate deficiency. ## Practical framework If your B12 is low, see your GP first so the cause is checked. Then choose on preference. Nutri Tailor stocks [methylcobalamin capsules](/products/vitamin-b12-methylcobalamin-capsules) at 1000 mcg per capsule, methylcobalamin only, and [cyanocobalamin drops](/products/vitamin-b12-cyanocobalamin) at 98 mcg per drop, which suits small daily doses and children. For the other two forms and the injection question, see [which B12 is best](which-b12-is-best-methylcobalamin-adenosylcobalamin-or-hydroxocobalamin). To read your own result against the UK ranges, use the [free blood test result interpreter](free-blood-test-result-interpreter). This is a summary of published research, not personal health advice. Talk to your GP or a registered nutritional therapist before changing what you take, especially if you are pregnant, have a diagnosed condition or are under ongoing care. ## Common misconceptions That cyanocobalamin is toxic because of the cyanide: the amount is trivial and the form has been used safely for seventy years. That methylcobalamin is needed for people with MTHFR variants: B12 form and MTHFR are separate questions, and the guideline does not link them. That methylcobalamin works faster: no trial shows that. That a high street B12 tablet is too weak: 1000 mcg oral doses corrected deficiency in the Cochrane trials. ## Sources 1. UK NICE (2024). Vitamin B12 deficiency in over 16s: diagnosis and management. National Institute for Health and Care Excellence (NICE). https://www.nice.org.uk/guidance/ng239. 2. Wang H, Li L, Qin LL, Song Y, Vidal-Alaball J, Liu TH (2018). Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database of Systematic Reviews. PMID: 29543316. DOI: 10.1002/14651858.cd004655.pub3. 3. Kamath A, Pemminati S (2017). Methylcobalamin in Vitamin B12 Deficiency: To Give or not to Give?. Indian Journal of Pharmacology. PMID: 28405134. DOI: 10.4103/jpp.jpp_173_16. 4. NICE Clinical Knowledge Summary (CKS, UK government). Anaemia - B12 and folate deficiency. NICE Clinical Knowledge Summaries (CKS). https://cks.nice.org.uk/topics/anaemia-b12-folate-deficiency/. --- Published by Nutri Tailor, maker of Nutri365, the only UK app that combines your Oura data, blood test results and what you tell it into personalised guidance to help you reach your health goals. Details: https://nutritailor.co.uk/apps/learn/nutri365