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Vitamin B1

Supplement vitamin energybrain & mood
Aka: thiamine, thiamin
Brands seen in Singapore: California Gold Nutrition, NOW Foods, Life Extension, Thorne, Nature's Way
Third-party tested: Thorne certifies other products with NSF Certified for Sport, but nothing for vitamin b1.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
Energy metabolism · growth and function of cells
When to take
No timing rule · short half-life, so a steady supply matters
Take with
Water · active transport at food doses, diffusion at high
Pros & cons
Pros
  • RDA is small — 1.2 mg men / 1.1 mg women
  • No UL — no adverse effects reported at 50 mg/day+
  • Excess is excreted in the urine
Cons
  • Absorption falls sharply at intakes above 5 mg
  • Diabetes/heart-failure trials: too small to conclude
  • SG caps B1 in health supplements at 100 mg/day
Sources
  1. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Introduction · read 2026-08-27
    what it says
    “Thiamin (or thiamine) is one of the water-soluble B vitamins. It is also known as vitamin B1 … This vitamin plays a critical role in energy metabolism and, therefore, in the growth, development, and function of cells”
  2. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Introduction (absorption) · read 2026-08-27
    what it says
    “Ingested thiamin from food and dietary supplements is absorbed by the small intestine through active transport at nutritional doses and by passive diffusion at pharmacologic doses”
  3. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Introduction (storage, half-life) · read 2026-08-27
    what it says
    “Humans store thiamin primarily in the liver but in very small amounts. The vitamin has a short half-life, so people require a continuous supply of it from the diet”
  4. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Table 1 RDAs + DV note · read 2026-08-27
    what it says
    “Table 1: Recommended Dietary Allowances (RDAs) for Thiamin … 19–50 years 1.2 mg 1.1 mg 1.4 mg 1.4 mg … 51+ years 1.2 mg 1.1 mg … The DV for thiamin is 1.2 mg for adults and children age 4 years and older”
  5. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Dietary supplements · read 2026-08-27
    what it says
    “Multivitamin/mineral supplements with thiamin typically provide about 1.5 mg thiamin … The most commonly used forms of thiamin in supplements are thiamin mononitrate and thiamin hydrochloride … Benfotiamine is not water soluble and is converted to thiamin in the body”
  6. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Groups at risk (alcohol, older adults) · read 2026-08-27
    what it says
    “chronic alcohol use disorders appear to be the most common cause of thiamin deficiency … Up to 20%–30% of older adults have laboratory indicators that suggest some degree of thiamin deficiency”
  7. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Groups at risk (bariatric surgery, diabetes) · read 2026-08-27
    what it says
    “Bariatric surgery for weight loss is associated with some risks, including severe thiamin deficiency due to malabsorption … thiamin levels in plasma are up to 76% lower in people with type 1 diabetes than in healthy volunteers”
  8. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Thiamin and health (diabetes, heart failure) · read 2026-08-27
    what it says
    “Well-designed studies with larger sample sizes and longer durations are required to determine whether thiamin supplements can reduce glucose levels in patients with diabetes … More research is needed to determine whether thiamin supplements might benefit people with heart failure”
  9. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Health risks from excessive thiamin · read 2026-08-27
    what it says
    “The body excretes excess amounts of thiamin in the urine. Because of the lack of reports of adverse effects from high thiamin intakes (50 mg/day or more) from food or supplements, the FNB did not establish ULs for thiamin”
  10. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Health risks from excessive thiamin (cont.) · read 2026-08-27
    what it says
    “the apparent lack of toxicity may be explained by the rapid decline in absorption of thiamin at intakes above 5 mg … in spite of the lack of reported adverse events, excessive intakes of thiamin could have adverse effects”
  11. NIH ODS — Thiamin (Health Professional), updated February 9, 2023 — Interactions with medications · read 2026-08-27
    what it says
    “Research has linked the use of furosemide to decreases in thiamin concentrations, possibly to deficient levels, as a result of urinary thiamin loss … several cases of beriberi or Wernicke's encephalopathy resulting from treatment with this drug [fluorouracil]”
  12. HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020 (January 2026), s4.8 general-adult limits, Table 4 Vitamins Limits + List of Health Claims rows 23, 56, 80 · read 2026-08-27
    what it says
    “Table 4: Vitamins Limits … Vitamin B1 100mg … Contribute to normal energy-yielding metabolism … Biotin, vitamin B1, B2, B3, B5, B6, C, D … Maintain/support energy production … Vitamin B1, B5 … Maintain/support nervous system function … Biotin, vitamin B1, B2, B3, B6”
  13. HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev. 001 (October 2025), Annex A row 108 · read 2026-08-27
    what it says
    “108. Vitamin B1 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 100mg”
  14. FDA — Daily Value on the Nutrition and Supplement Facts Labels (Reference Guide: Daily Values for Nutrients), content current as of 03/05/2024 · read 2026-08-27
    what it says
    “Thiamin 1.2mg … DVs are the recommended amounts of nutrients to consume or not to exceed each day”
  15. iHerb Singapore — Vitamin B1 Thiamine category page (default order), first listings · read 2026-08-27
    what it says
    “1 - 19 of 19 results … California Gold Nutrition, Benfotiamine with Thiamine, 250 mg … NOW Foods, B-1, 100 mg … Life Extension, Mega Benfotiamine … Thorne, B-Complex #12 … Nature's Way, Vitamin B1, 100 mg”
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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.