Thiamine (Vitamin B1) Supplements

Food sources include pork, fish, whole grains, fortified foods and legumes. Common supplement forms are thiamine mononitrate and thiamine hydrochloride. Benfotiamine is a different synthetic derivative; evidence for one preparation should not be assumed to prove the effects of every B1 product.^{See reference 1}

NHS describes thiamine medicines as treatment or prevention for deficiency. Too little thiamine can affect the nervous system and heart. Deficiency related to illness, poor absorption or alcohol problems needs assessment of the cause and an appropriate treatment plan; this guide does not supply a regimen.^{See reference 1,See reference 2}

A 2024 meta-analysis included seven randomised, double-blind trials with 274 people who had chronic heart failure. Pooled results did not show a clear improvement in heart pumping function, walking distance or the other reported clinical measures, although thiamine status improved.^{See reference 3}

These were small studies with varying results and regimens. The finding does not make deficiency treatment unnecessary. It also cannot establish a benefit for healthy people, a particular shop product or a longevity claim. A biochemical role is not the same as a demonstrated additional treatment effect.^{See reference 3}

A 2019 acute-heart-failure trial randomised 130 people; 118 had evaluable data, and only one had thiamine deficiency. The study used 100 mg thiamine or placebo on the first two evenings. Thiamine levels increased, but the authors did not find an overall improvement in breathlessness, biomarkers or the other clinical measures.^{See reference 4}

The amount is a description of a hospital trial, not a home supplement dose. One breathlessness measurement differed between groups, while the other measurements did not. That mixed result is more informative than selecting a single positive number and calling the treatment successful.^{See reference 4}

The U.S. FDA Daily Value for thiamin is 1.2 mg for adults and children aged four and over. It is a labelling reference, not a personal prescription; other label systems or populations may use different references.^{See reference 1,See reference 5}

For example, a label amount of 1.2 mg against a 1.2 mg reference is 100%. An invented 12 mg amount is 1,000% of that reference. This tenfold difference describes quantity, not ten times the benefit. Read both the amount and serving size.

The U.S. Food and Nutrition Board did not set a tolerable upper intake level for thiamine because adverse-effect evidence was insufficient. NIH still cautions that excessive intake could cause harm. Lack of a limit is not proof that any dose is useful or safe.^{See reference 1}

Medicines such as furosemide and fluorouracil can affect thiamine status. That calls for a professional review, not automatic supplementation or changing a medicine yourself. Include combination products when describing what you take.^{See reference 1}

NHS lists nausea and stomach ache among usually mild side effects of thiamine medicine. Report troublesome effects and follow the instructions for the prescribed product.^{See reference 2}