vitamin B-1, thiamin (U.S. spelling), thiamine (European spelling)
Thiamin is a part of the B family of vitamins (B complex). It was the first water-soluble vitamin discovered. It is also known as vitamin B-1. Like all B vitamins, thiamin is best known for helping make energy. Beriberi and Wernicke-Korsakoff syndrome are the most common diseases linked with thiamin deficiency. But they are not common in the U.S.
Thiamin is needed to turn glucose and carbohydrates into energy. It works with other enzymes in more than 20 metabolic processes.
Thiamin is also needed for the nervous system and the brain to work well. Because thiamin is needed for nerve function, low levels can lead to nerve problems.
Thiamin is used to treat or prevent beriberi. It’s also used to treat Wernicke-Korsakoff syndrome (WKS). This is a severe thiamin deficiency. It’s caused by a low intake of and less ability to use thiamin. It’s common in people with any of these:
A severe digestive disorder
Fast-growing blood cancer
Drug use disorders
There may be benefits that have not yet been proven through research.
Thiamin may repel mosquitoes. It may also lower blood sugar levels in people with diabetes. More studies are needed to see if thiamin supplements can lower glucose levels in people with diabetes or lessen problems from diabetes.
It may also help improve mental stability. It’s also been used to boost appetite. It may also treat rare metabolic issues related to learning disabilities.
How much thiamin you need depends on how many calories from carbohydrates you get in your diet. The more carbohydrates you eat, the more thiamin you need. Thiamin is measured in milligrams (mg). Adults need about 0.4 mg to 0.5 mg for every 1,000 calories they eat.
The RDA in the chart below is the Recommended Dietary Allowance.
Infants (0 to 6 months)
Infants (7 months to 1 year)
Children (1 to 3 years)
Children (4 to 8 years)
Children (9 to 13 years)
Males (14 years and older)
Females (14 to 18 years)
Females (19 years and older)
*Adequate Intake (AI). This is based on the average intake in healthy, breastfed infants.
Nutrient content per 100 grams
Dried yeast, baker's
Pistachios, dry roasted
Thiamin is not stable at high temperatures. Because of this, cooking reduces its amount in food by 10% to 25%. Thiamin dissolves in water. So if you cook foods high in thiamin in water and then discard the water, you won’t get as much thiamin.
Using sulfur dioxide to preserve dried fruit will destroy the thiamin content.
Thiamin is sensitive to light. Store foods with thiamin in light-resistant containers.
Thiamin supplements may be needed for any of the below:
People with alcoholism or heavy alcohol use
People who eat diets high in refined carbohydrates
Breastfed babies whose mothers have a poor diet
People with hyperthyroidism
People with hypermetabolic problems, such as pheochromocytoma
People who have a lot of stress
People doing a lot of heavy physical activity
Women who are pregnant or breastfeeding (talk with your healthcare provider first)
Older adults with poor diets and natural decrease of absorption due to aging
Early symptoms of thiamin deficiency include:
Loss of appetite
Severe tiredness (fatigue)
Short-term memory loss
Later symptoms may include:
The later stages of thiamin deficiency can turn into beriberi. This includes dry beriberi, wet beriberi, and Wernicke-Korsakoff syndrome.
Dry beriberi can cause nerve and muscle problems. It can cause peripheral nerve changes (polyneuritis). Symptoms of dry beriberi may include:
Numbness and tingling of toes
Burning feeling in feet
Pain in the legs with muscle cramping and wasting (atrophy)
Wet beriberi is linked to cardiovascular disease. Symptoms can include:
Increased heart rate
Right-side heart failure
Symptoms of Wernicke-Korsakoff syndrome include:
Loss of memory
Confusion between real and imagined memories
In the U.S., WKS is often linked with alcoholism. If the damage from WKS isn’t too severe, it can often be quickly reversed with thiamin. If not treated, it can lead to coma and death.
There are no known side effects of too much thiamin. Extra thiamin comes out in the urine.
You shouldn’t take thiamin if you’re allergic to it.
There are no known food interactions with thiamin.
Furosemide is a loop diuretic used to treat edema and hypertension that may decrease thiamin levels by increasing urinary output.