Vitamin B1 (Thiamine)
Also known as: Thiamine, Thiamin Hydrochloride, Benfotiamine
Thiamine is a critical component of thiamine pyrophosphate (TPP), a coenzyme involved in key metabolic reactions such as the decarboxylation of alpha-keto acids (e.g., pyruvate, alpha-ketoglutarate) and the transketolase reaction in the pentose phosphate pathway. These reactions are vital for ATP production and the synthesis of nucleic acids and NADPH. Thiamine deficiency can lead to serious neurological and cardiovascular issues, collectively known as beriberi or Wernicke-Korsakoff syndrome.
Last reviewed: 2026-04-22 · 4 indexed studies
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Overview
Vitamin B1, or Thiamine, is a water-soluble vitamin essential for various metabolic processes, particularly carbohydrate metabolism. It acts as a coenzyme in the conversion of food into energy.
Mechanism & Function
Thiamine · C₁₂H₁₇N₄OS⁺ — source: PubChem CID 1130
White-to-cream crystalline B-vitamin (thiamine HCl or mononitrate). Water-soluble.
- Capsule
- Tablet
- Powder
- Liquid
Capsule is generally preferred for bioavailability or efficacy.
Mechanism of Action
Thiamine, in its active form thiamine pyrophosphate (TPP), functions as a coenzyme for several crucial enzymes. These include pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain alpha-keto acid dehydrogenase, all of which are central to carbohydrate and amino acid metabolism. TPP is also a coenzyme for transketolase in the pentose phosphate pathway, important for nucleotide synthesis and maintaining redox balance.
Physiological Role
Thiamine plays a pivotal role in energy metabolism, particularly the breakdown of carbohydrates to glucose. It is essential for nerve function, as glucose is the primary energy source for the brain. It also contributes to the synthesis of neurotransmitters and the maintenance of myelin sheaths. Its role in the pentose phosphate pathway is critical for generating NADPH and ribose-5-phosphate, necessary for antioxidant defense and nucleic acid synthesis, respectively.
Primary Pathways
Performance / Health Relevance
While thiamine does not directly enhance athletic performance in individuals with adequate intake, it is crucial for sustaining energy production from carbohydrates. Deficiency can significantly impair energy levels, muscle function, and neurological coordination, thereby negatively impacting performance. Supplementation is primarily relevant for preventing deficiency in at-risk populations (e.g., alcoholics, individuals with malabsorption, very high carbohydrate diets without adequate intake).
Evidence Review
Practical Use & Dosage
- Minimum Effective Dose
- 1.2 mg/day (RDA for adult males)
- Optimal Range
- 1.2-2 mg/day for general health; higher doses (e.g., 100-300 mg/day) for specific deficiencies under medical supervision.
- Upper / Caution Level
- No observed adverse effects from high thiamine intake from food or supplements due to its water-soluble nature and rapid excretion of excess.
- Timing
- Can be taken with or without food, typically once daily.
- Best Format
- Oral tablets or capsules. Benfotiamine (a lipid-soluble derivative) may offer superior bioavailability in some contexts.
- Bioavailability
- Water-soluble and readily absorbed in the small intestine. Absorption can be impaired by alcohol, certain medications, and antinutritional factors in food.
- Absorption Considerations
- Active transport at low concentrations, passive diffusion at high concentrations. Alcohol and sulfites can inhibit absorption. High doses of other B vitamins do not typically interfere.
Safety & Interactions
Side Effects
- •Rarely, mild gastrointestinal upset with very high oral doses.
Contraindications
- None known for oral supplementation within normal ranges.
Drug Interactions
- •Diuretics (e.g., furosemide) may increase excretion, potentially leading to deficiency.
- •Fluorouracil (chemotherapy drug) can interfere with thiamine metabolism.
Who Should Avoid
- •Individuals with known hypersensitivity to thiamine (extremely rare).
Monitoring
Monitoring thiamine status is typically only necessary in at-risk populations (e.g., chronic alcoholics, bariatric surgery patients, individuals with malabsorption syndromes).
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is Vitamin B1 (Thiamine) typically used or indicated?
Vitamin B1 (Thiamine) is most commonly used for: Metabolism support, Nerve health, Energy production. Thiamine plays a pivotal role in energy metabolism, particularly the breakdown of carbohydrates to glucose. It is essential for nerve function, as glucose is the primary energy source for the brain. It also contributes to the synthesis of neurotransmitters and the maintenance of myelin sheaths. Its role in the pentose phosphate pathway is critical for generating NADPH and ribose-5-phosphate, necessary for antioxidant defense and nucleic acid synthesis, respectively.
How does Vitamin B1 (Thiamine) work?
Thiamine, in its active form thiamine pyrophosphate (TPP), functions as a coenzyme for several crucial enzymes. These include pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain alpha-keto acid dehydrogenase, all of which are central to carbohydrate and amino acid metabolism. TPP is also a coenzyme for transketolase in the pentose phosphate pathway, important for nucleotide synthesis and maintaining redox balance.
What is the recommended dose of Vitamin B1 (Thiamine)?
The optimal range is 1.2-2 mg/day for general health; higher doses (e.g., 100-300 mg/day) for specific deficiencies under medical supervision.. with a minimum effective dose of 1.2 mg/day (RDA for adult males). Best taken: Can be taken with or without food, typically once daily.. Upper / caution level: No observed adverse effects from high thiamine intake from food or supplements due to its water-soluble nature and rapid excretion of excess..
What are the side effects of Vitamin B1 (Thiamine)?
Reported side effects include: Rarely, mild gastrointestinal upset with very high oral doses.. Monitoring: Monitoring thiamine status is typically only necessary in at-risk populations (e.g., chronic alcoholics, bariatric surgery patients, individuals with malabsorption syndromes).
Does Vitamin B1 (Thiamine) interact with medications?
Known or theoretical interactions: Diuretics (e.g., furosemide) may increase excretion, potentially leading to deficiency.; and Fluorouracil (chemotherapy drug) can interfere with thiamine metabolism.. Always check with a clinician before combining with prescription medication.
Who should avoid Vitamin B1 (Thiamine)?
Vitamin B1 (Thiamine) is generally not recommended for: Individuals with known hypersensitivity to thiamine (extremely rare).; and None known for oral supplementation within normal ranges..
How strong is the evidence for Vitamin B1 (Thiamine)?
Evidence level: Moderate (overall score 65/100), based on 4 indexed studies on SuppIndex.
Research & References (4)
Thiamine deficiency and implications for the kidney and liver
This review summarizes the role of thiamine in metabolic processes and the systemic consequences of its deficiency, particularly focusing on kidney and liver function. It highlights that thiamine deficiency, even subclinical, can impair organ function and energy metabolism.
Thiamine (vitamin B1) and its derivatives in the treatment of diabetes mellitus: A review
Reviews the therapeutic potential of thiamine and its derivatives (e.g., benfotiamine) in managing diabetes and its complications by addressing underlying metabolic dysfunction, particularly advanced glycation end-product (AGE) formation.
Thiamine in health and disease: a review of the literature 1990-2000
This comprehensive review examines various aspects of thiamine, including its biochemistry, metabolism, deficiency states, and therapeutic uses over a decade of research. It covers a broad spectrum of conditions associated with thiamine status.
Wernicke-Korsakoff syndrome: a clinical review
A review focusing on Wernicke-Korsakoff syndrome, a serious neuropsychiatric disorder primarily caused by thiamine deficiency, often associated with chronic alcoholism. It details the pathophysiology, clinical presentation, and management including thiamine supplementation.
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Research Overview
Moderate EvidenceCite this ingredient
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Stable URL
https://thesuppindex.com/ingredients/vitamin-b1-thiamine
SuppIndex. (2026). Vitamin B1 (Thiamine): Evidence summary, dosage and clinical studies. Retrieved October 23, 2026, from https://thesuppindex.com/ingredients/vitamin-b1-thiamine
Based on 4 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Generally safe and compatible with most supplements. Often included in B-complex formulations.