{"ok":true,"entry":{"slug":"methylcobalamin","kind":"supplement","name":"methylcobalamin","aliases":["methyl B-12","methyl B12"],"brands_sg":["California Gold Nutrition","NOW Foods","Life Extension","Doctor's Best","Thorne"],"class":"vitamin B12 form","tags":["energy","cognitive"],"use_for":"an active b12 form · red cells, nerves, dna synthesis","use_after":"no timing rule","use_duration":null,"take_with":"water · absorption is only about 2% at a 500 mcg dose","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"],"dose_note":"the b12 rda is 2.4 mcg a day for adults (2.6 mcg in pregnancy, 2.8 mcg when breastfeeding) and the fda daily value is 2.4 mcg; the fnb set no ul, citing low potential for toxicity — which is an absence of a limit, not a safety finding; hsa's singapore limit for health supplements is 0.6 mg (600 mcg) a day and applies to vitamin b12 as a whole, methylcobalamin included; b12-only supplements typically carry 500–1,000 mcg, of which about 2% (500 mcg) and 1.3% (1,000 mcg) is absorbed, so most sg listings sit at or above the hsa cap; after roux-en-y gastric bypass, 1,000 mcg/day oral methylcobalamin appeared as effective as hydroxocobalamin injections; on the two tags: hsa allows an energy-metabolism claim for b12, but the nih sheet says supplementation appears to have no beneficial effect on performance without a deficit, and rcts of 1–2 years show no cognitive gain in older adults","dosage":{"ul":null,"unit":"mcg","fda_dv":2.4,"rda_ai":2.4,"ul_status":"none_established","population":"general adult","hsa_max_daily":600},"ul_status":"none_established","sg_class":null,"cautions":["pernicious anemia or stomach/bowel surgery — absorption is impaired; ask your doctor","on metformin — it might reduce b12 absorption and serum b12; ask about a blood test","on ppis or h2 blockers — less gastric acid frees less b12 from food","most sg listings (500–1,000 mcg) sit above hsa's 0.6 mg supplement cap"],"clashes":[{"src":["nih_ods_b12_interactions"],"note":"slow the release of gastric acid, interfering with b12 absorption from food and leading to deficiency","with":"proton pump inhibitors (omeprazole, lansoprazole)"},{"src":["nih_ods_b12_interactions"],"note":"same acid-lowering effect on b12 released from food","with":"h2 blockers (cimetidine, ranitidine)"},{"src":["nih_ods_b12_interactions"],"note":"might reduce b12 absorption and significantly reduce serum b12 concentrations","with":"metformin"}],"sources":[{"id":"nih_ods_b12_forms","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional), updated July 2, 2025 — Introduction (read via archive.org capture, see verify_notes)","quote":"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","accessed":"2026-08-27"},{"id":"nih_ods_b12_function","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Introduction, function","quote":"Vitamin B12 is required for the development, myelination, and function of the central nervous system; healthy red blood cell formation; and DNA synthesis","accessed":"2026-08-27"},{"id":"nih_ods_b12_rda","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Table 1 RDAs and the DV note","quote":"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","accessed":"2026-08-27"},{"id":"nih_ods_b12_absorb","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Sources, dietary supplements","quote":"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","accessed":"2026-08-27"},{"id":"nih_ods_b12_supp","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Sources, supplement forms and typical doses","quote":"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","accessed":"2026-08-27"},{"id":"nih_ods_b12_sublingual","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Sources, sublingual preparations","quote":"vitamin B12 is available in sublingual preparations as tablets or lozenges … Evidence suggests no difference in efficacy between oral and sublingual forms","accessed":"2026-08-27"},{"id":"nih_ods_b12_bypass","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Groups at Risk, gastrointestinal surgery","quote":"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","accessed":"2026-08-27"},{"id":"nih_ods_b12_ul","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Health Risks from Excessive Vitamin B12","quote":"The FNB did not establish a UL for vitamin B12 because of its low potential for toxicity","accessed":"2026-08-27"},{"id":"nih_ods_b12_energy","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Vitamin B12 and Health, energy and endurance","quote":"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","accessed":"2026-08-27"},{"id":"nih_ods_b12_cognition","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Vitamin B12 and Health, dementia and cognitive function","quote":"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","accessed":"2026-08-27"},{"id":"nih_ods_b12_interactions","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional) — Interactions with Medications","quote":"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","accessed":"2026-08-27"},{"id":"hsa_prohibited","url":"https://file.go.gov.sg/hsa-chp-prohibited-restricted-ing-guidelines.pdf","label":"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","quote":"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","accessed":"2026-08-27"},{"id":"hsa_hs_guidelines","url":"https://file.go.gov.sg/hsa-hs-guidelines.pdf","label":"HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020 (January 2026), clause 4.8 and Table 4 Vitamins Limits","quote":"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","accessed":"2026-08-27"},{"id":"iherb_sg","url":"https://sg.iherb.com/c/vitamin-b12","label":"iHerb Singapore — Vitamin B12 (Cobalamin) category page, default listing order","quote":"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","accessed":"2026-08-27"}],"brand_certs":[{"brand":"Thorne","example":null,"programme":"NSF Certified for Sport","matching_products":0,"brand_total_certified":66}],"updated_at":"2026-08-30T17:59:38.376296+08:00"},"disclaimer":"kozen-x is not a medical device and does not give medical advice. it lists what published sources have written down. absence of a record is not the same as safe."}