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Methylcobalamin

Supplement vitamin B12 form energybrain & mood
Aka: methyl B-12, methyl B12
Brands seen in Singapore: California Gold Nutrition, NOW Foods, Life Extension, Doctor's Best, Thorne
Third-party tested: Thorne certifies other products with NSF Certified for Sport, but nothing for methylcobalamin.Certification is granted per product, so check the tub you actually own. Not being listed is not the same as failing.
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
An active B12 form · red cells, nerves, DNA synthesis
When to take
No timing rule
Take with
Water · absorption is only about 2% at a 500 mcg dose
Pros & cons
Pros
  • One of the two metabolically active B12 forms
  • No evidence a B12 form absorbs better than another
  • No UL set — fnb cites low potential for toxicity
Cons
  • Absorption ~2% at 500 mcg, 1.3% at 1,000 mcg
  • No performance gain without a nutritional deficit
  • SG caps B12 supplements at 0.6 mg (600 mcg) a day
Sources
  1. NIH ODS — Vitamin B12 (Health Professional), updated July 2, 2025 — Introduction (read via archive.org capture, see verify_notes) · read 2026-08-27
    what it says
    “Methylcobalamin and 5-deoxyadenosylcobalamin are the metabolically active forms of vitamin B12. However, two others forms, hydroxycobalamin and cyanocobalamin, become biologically active after they are converted to methylcobalamin or 5-deoxyadenosylcobalamin”
  2. NIH ODS — Vitamin B12 (Health Professional) — Introduction, function · read 2026-08-27
    what it says
    “Vitamin B12 is required for the development, myelination, and function of the central nervous system; healthy red blood cell formation; and DNA synthesis”
  3. NIH ODS — Vitamin B12 (Health Professional) — Table 1 RDAs and the DV note · read 2026-08-27
    what it says
    “19+ years 2.4 mcg 2.4 mcg 2.6 mcg 2.8 mcg … The DV for vitamin B12 is 2.4 mcg for adults and children age 4 years and older”
  4. NIH ODS — Vitamin B12 (Health Professional) — Sources, dietary supplements · read 2026-08-27
    what it says
    “No evidence indicates that absorption rates of vitamin B12 in supplements vary by form of the vitamin … absorption is only about 2% at doses of 500 mcg and 1.3% at doses of 1,000 mcg”
  5. NIH ODS — Vitamin B12 (Health Professional) — Sources, supplement forms and typical doses · read 2026-08-27
    what it says
    “Vitamin B12 levels are higher … typically 500 to 1,000 mcg, in supplements containing only vitamin B12 … The most common form of vitamin B12 in dietary supplements is cyanocobalamin … Other forms … are adenosylcobalamin, methylcobalamin, and hydroxycobalamin”
  6. NIH ODS — Vitamin B12 (Health Professional) — Sources, sublingual preparations · read 2026-08-27
    what it says
    “vitamin B12 is available in sublingual preparations as tablets or lozenges … Evidence suggests no difference in efficacy between oral and sublingual forms”
  7. NIH ODS — Vitamin B12 (Health Professional) — Groups at Risk, gastrointestinal surgery · read 2026-08-27
    what it says
    “High doses (1,000 mcg/day) of oral methylcobalamin supplements appear to be as effective as hydroxocobalamin injections in normalizing vitamin B12 values in patients who have undergone Roux-en-Y gastric bypass surgery”
  8. NIH ODS — Vitamin B12 (Health Professional) — Health Risks from Excessive Vitamin B12 · read 2026-08-27
    what it says
    “The FNB did not establish a UL for vitamin B12 because of its low potential for toxicity”
  9. NIH ODS — Vitamin B12 (Health Professional) — Vitamin B12 and Health, energy and endurance · read 2026-08-27
    what it says
    “Because of its role in energy metabolism, vitamin B12 is often promoted as an energy enhancer … However, vitamin B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit”
  10. NIH ODS — Vitamin B12 (Health Professional) — Vitamin B12 and Health, dementia and cognitive function · read 2026-08-27
    what it says
    “evidence from RCTs does not show that vitamin B12 supplementation alone or with folic acid, vitamin B6, or both for 1 to 2 years improves cognitive function in older adults with or without dementia”
  11. NIH ODS — Vitamin B12 (Health Professional) — Interactions with Medications · read 2026-08-27
    what it says
    “Gastric acid inhibitors … can interfere with vitamin B12 absorption from food by slowing the release of gastric acid into the stomach … Metformin … might reduce the absorption of vitamin B12 and significantly reduce serum vitamin B12 concentrations”
  12. HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev. No. 001 (October 2025), Annex A row 112 · read 2026-08-27
    what it says
    “112. Vitamin B12 Restricted use in HS and TM Maximum Daily Dose When for oral use by general adult population, the maximum recommended daily dose should not provide more than 0.6mg”
  13. HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020 (January 2026), clause 4.8 and Table 4 Vitamins Limits · read 2026-08-27
    what it says
    “4.8 HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5 … Table 4: Vitamins Limits … Vitamin B12 0.6mg”
  14. iHerb Singapore — Vitamin B12 (Cobalamin) category page, default listing order · read 2026-08-27
    what it says
    “Vitamin B12 (Cobalamin) … 322 results … California Gold Nutrition, Gummiology® B Complex … NOW Foods, Methyl B-12, 1,000 mcg … Life Extension, Vitamin B12, Methylcobalamin … Doctor's Best, Fully Active B12 … Thorne, Vitamin B12”
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Updated 2026-08-30. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.