{"ok":true,"entry":{"slug":"vitamin-b12","kind":"supplement","name":"vitamin b12","aliases":["cobalamin","cyanocobalamin"],"brands_sg":["Kordel's","GNC","NOW Foods","Solgar"],"class":"vitamin","tags":["energy","cognitive"],"use_for":"red blood cells, nerve function and dna synthesis","use_after":"no timing rule","use_duration":null,"take_with":"water · already free-form, no stomach-acid release needed","pros":["no ul set — fnb cites low potential for toxicity","no form (cyano, methyl, hydroxo) shown to beat another","suits over-50s and vegans, who get less b12 from food"],"cons":["only ~2% of a 500 mcg dose is absorbed","no energy or performance boost unless you're deficient","metformin and acid blockers can lower b12 levels"],"dose_note":"rda 2.4 mcg a day for adults (2.6 mcg pregnancy, 2.8 mcg lactation); no ul; hsa's limit for health supplements is 0.6 mg (600 mcg) a day; b12-only pills typically carry 500–1,000 mcg, of which only about 2% (500 mcg) to 1.3% (1,000 mcg) is absorbed — many sg listings sit above the hsa cap","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 — pills absorb poorly; ask your doctor","on metformin or acid blockers — b12 can drop; ask about a blood test","vegan or vegetarian — food b12 is animal-only; deficiency risk is higher","over 50 — many absorb less b12 from food; fortified food or a supplement is advised"],"clashes":[{"src":["nih_ods_b12_hp","nih_ods_b12_con"],"note":"less stomach acid frees less b12 from food; can lead to deficiency","with":"proton pump inhibitors (omeprazole, lansoprazole)"},{"src":["nih_ods_b12_hp","nih_ods_b12_con"],"note":"same acid-lowering effect on b12 from food","with":"h2 blockers (cimetidine, ranitidine)"},{"src":["nih_ods_b12_hp","nih_ods_b12_con"],"note":"may reduce b12 absorption and lower serum b12","with":"metformin"}],"sources":[{"id":"nih_ods_b12_hp","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/","label":"NIH ODS — Vitamin B12 (Health Professional), updated July 2, 2025","quote":"[RDA] 19+ years: Male 2.4 mcg, Female 2.4 mcg, Pregnancy 2.6 mcg, Lactation 2.8 mcg … Vitamin B12 is required for the development, myelination, and function of the central nervous system; healthy red blood cell formation; and DNA synthesis … If vitamin B12 is added to fortified foods and dietary supplements, it is already in free form and therefore does not require the separation step … The most common form of vitamin B12 in dietary supplements is cyanocobalamin … Other forms of vitamin B12 in supplements are adenosylcobalamin, methylcobalamin, and hydroxycobalamin … 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 … typically 500 to 1,000 mcg, in supplements containing only vitamin B12 … Evidence suggests no difference in efficacy between oral and sublingual forms … The FNB did not establish a UL for vitamin B12 because of its low potential for toxicity … vitamin B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit … Gastric acid inhibitors include proton pump inhibitors, such as omeprazole (Prilosec) and lansoprazole (Prevacid), and histamine 2-receptor antagonists, such as cimetidine (Tagamet) and ranitidine (Zantac) … They can interfere with vitamin B12 absorption from food by slowing the release of gastric acid into the stomach and thereby lead to vitamin B12 deficiency … Metformin, an antihyperglycemic agent used as first-line treatment for prediabetes and diabetes, might reduce the absorption of vitamin B12 and significantly reduce serum vitamin B12 concentrations … Vegans who consume no animal products and vegetarians who consume some animal products (e.g., dairy products, eggs, or both) but not meat have a higher risk of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods … [pernicious anemia] resulting in failure to produce intrinsic factor and malabsorption of dietary vitamin B12 … Surgical procedures in the gastrointestinal tract, such as for weight loss or to remove all or part of the stomach, can cause a complete or partial loss of cells that secrete hydrochloric acid and cells that secrete intrinsic factor","accessed":"2026-08-27"},{"id":"nih_ods_b12_con","url":"https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/","label":"NIH ODS — Vitamin B12 (Consumer), updated December 15, 2023","quote":"Vitamin B12 is a nutrient that helps keep your body's blood and nerve cells healthy and helps make DNA, the genetic material in all of your cells … Adults 2.4 mcg … Vitamin B12 in dietary supplements isn't attached to protein and doesn't require the first step. However, B12 in supplements does need to combine with intrinsic factor to be absorbed … People over 50 should get most of their vitamin B12 from fortified foods or dietary supplements because, in most cases, their bodies can absorb vitamin B12 from these sources … People with pernicious anemia do not make the intrinsic factor needed to absorb vitamin B12. As a result, they have trouble absorbing vitamin B12 from foods and dietary supplements … Your doctor can test your vitamin B12 level to see if you have a deficiency … Gastric acid inhibitors include omeprazole (Prilosec), lansoprazole (Prevacid), cimetidine (Tagamet), and ranitidine (Zantac) … Metformin might reduce vitamin B12 absorption and lower blood levels of vitamin B12 … Vitamin B12 is also available in a form that's dissolved under your tongue (called sublingual vitamin B12). Research has not shown that any form of supplemental vitamin B12 is better than the others","accessed":"2026-08-27"},{"id":"fda_dv","url":"https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels","label":"FDA — Daily Value on the Nutrition and Supplement Facts Labels (Reference Guide: Daily Values for Nutrients), content current as of 03/05/2024","quote":"Vitamin B12 … 2.4mcg … DVs are the recommended amounts of nutrients to consume or not to exceed each day","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 + 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 … Nutrient … Maximum Daily Limit … Vitamin B12 0.6mg","accessed":"2026-08-27"},{"id":"watsons_sg_b12","url":"https://www.watsons.com.sg/search?text=vitamin%20b12","label":"Watsons Singapore — site search 'vitamin b12' (retail listings, SGD)","quote":"[KORDEL'S] Vitamin B12 Methylcobalamin 500mcg 120s … [GNC] Vitamin B12 500mcg Tablet 90s … [GREENLIFE] Vitamin B12 (Supports Healthy Red Blood Cells And Immune System Function) 90s","accessed":"2026-08-27"},{"id":"iherb_sg_b12","url":"https://sg.iherb.com/search?kw=vitamin+b12","label":"iHerb Singapore — search 'vitamin b12' (retail listings)","quote":"NOW Foods, Methyl B-12, 1,000 mcg, 100 Lozenges … Solgar, Vitamin B12, 500 mcg, 100 Tablets … Solgar, Vitamin B 12, Sublingual, 1,000 mcg, 100 Nuggets … Jarrow Formulas, Methyl B-12, Lemon, 1,000 mcg, 100 Chewable Tablets … Nutricost, Vitamin B12, 5,000 mcg, 120 Capsules","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:34.039038+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."}