Vitamin B1
Thiamin helps cells use energy from food.
The formula matches the form shown in the 3D model. Other forms of this vitamin can have different formulas.Loading molecular structure…
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One representative form. Hydrogens omitted; bonds simplified.
PubChem · CID 1130Where you can find it
- Whole grains
- Fortified cereals
- Pork
- Beans
- Seeds
What it does in the body
Thiamin supports energy metabolism and normal cell function.
Recommended amounts & upper limit
US reference values for healthy adults aged 19–50, excluding pregnancy and breastfeeding. These are daily dietary intakes, not blood-test ranges or prescribed supplement doses. Other ages and life stages have different needs; see the original source.
- Men · RDA
- 1.2 mg/day
- Women · RDA
- 1.1 mg/day
- Upper limit · UL
- No established ULEvidence is insufficient to set an upper intake limit.
How to read these levels
RDA means Recommended Dietary Allowance; AI means Adequate Intake, used when an RDA cannot be set. The upper limit (UL) is not a target or an exact toxicity threshold. Going below the RDA on one day does not diagnose deficiency. No established UL does not mean unlimited amounts are safe.
mg = milligrams; mcg = micrograms. 1 mg = 1,000 mcg. IU is vitamin-specific and cannot be converted with one rule for all vitamins.
What happens when the balance changes?
These are possible effects, not a diagnosis or a prediction from one low or high result.
Too little
Deficiency may cause weakness, weight loss, confusion and memory problems. Severe deficiency can cause beriberi, with nerve and heart problems, or Wernicke–Korsakoff syndrome.
Body areas affected
Brain, peripheral nerves, muscles and heart.
Too much
Oral thiamin has not been shown to cause harm at high intakes, but this does not establish that every dose is safe.
Body areas affected
No specific organ toxicity established for oral intake.
What about blood-test levels?
Blood-test levels and daily intake use different units and cannot be compared directly. Test methods, reference ranges and clinical context vary. Symptoms alone cannot establish a vitamin deficiency or toxicity; a clinician can decide which tests and treatment are appropriate.
The body connection
The nervous system and heart are especially affected by severe deficiency.
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