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Vitamin B1

Also indexed as: Thiamin, Thiamine


Vitamin B1 is is a water-soluble vitamin needed to process carbohydrates, fat, and protein. Every cell of the body requires vitamin B1 to form the fuel the body runs on—adenosine triphosphate (ATP). Nerve cells require vitamin B1 in order to function normally.

Where is it found?

Wheat germ, whole wheat, peas, beans, enriched flour, fish, peanuts, and meat are all good sources of vitamin B1.

Vitamin B1 has been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings Health Concerns

Anemia (for genetic thiamine-responsive anemia)


Alzheimer’s disease

Canker sores

Childhood intelligence (for deficiency)

Dialysis (for encephalopathy and neurologic damage; take only under medical supervision)


Low back pain (in combination with vitamin B6 and vitamin B12)

Type 1 diabetes

Type 2 diabetes


Cardiomyopathy (only for wet beri beri)

Dysmenorrhea (painful menstruation)


HIV support

Multiple sclerosis

Pre- and post-surgery health

3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Who is likely to be deficient?

A decline in vitamin B1 levels occurs with age, irrespective of medical condition.1 Deficiency is most commonly found in alcoholics, people with malabsorption conditions, and those eating a very poor diet. It is also common in children with congenital heart disease.2 People with chronic fatigue syndrome may also be deficient in vitamin B1.3 4 Individuals undergoing regular kidney dialysis may develop severe vitamin B1 deficiency, which can result in potentially fatal complications.5 Persons receiving dialysis should discuss the need for vitamin B1 supplementation with their physician.

How much is usually taken?

While the ideal intake is uncertain, one study reported the healthiest people consumed more than 9 mg per day.6 The amount found in many multivitamin supplements (20–25 mg) is more than adequate for most people.

Vitamin B1 is nontoxic, even in very high amounts.

Are there any side effects or interactions?

Vitamin B1 works hand in hand with vitamin B2 and vitamin B3. Therefore, nutritionists usually suggest that vitamin B1 be taken as part of a B-complex vitamin or other multivitamin supplement.

Are there any drug interactions?
Certain medicines may interact with vitamin B1. Refer to drug interactions for a list of those medicines.


1. Wilkinson TJ, Hanger HC, George PM, Sainsbury R. Is thiamine deficiency in elderly people related to age or co-morbidity? Age Ageing 2000;29:111–6.

2. Shamir R, Dagan O, Abramovitch D, et al. Thiamine deficiency in children with congenital heart disease before and after corrective surgery. JPEN J Parenter Enteral Nutr 2000;24:154–8.

3. Heap LC, Peters TJ, Wessely S. Vitamin B status in patients with chronic fatigue syndrome. J R Soc Med 1999;92:183–5.

4. Grant JE, Veldee MS, Buchwald D. Analysis of dietary intake and selected nutrient concentrations in patients with chronic fatigue syndrome. J Am Diet Assoc 1996;96:383–6.

5. Hung SC, Hung SH, Tarng DC, et al. Thiamine deficiency and unexplained encephalopathy in hemodialysis and peritoneal dialysis patients. Am J Kidney Dis 2001;38:941–7.

6. Cheraskin E, Ringsdorf WM, Medford FH, Hicks BS. The “ideal” daily vitamin B1 intake. J Oral Med 1978; 33:77–9.

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