Thiamine (vitamin B1) is found in many foods and is used to treat low thiamine, beriberi, certain nerve diseases, and Wernicke-Korsakoff syndrome (WKS).

Thiamine is required by our bodies to properly use carbohydrates. It also helps maintain proper nerve function. It's found in foods such as yeast, cereal grains, beans, nuts, and meat. It's often used in combination with other B vitamins, and is found in many vitamin B complex products.

People take thiamine for conditions related to low levels of thiamine, including beriberi and inflammation of the nerves (neuritis). It's also used for digestive problems, diabetic nerve pain, heart disease, and other conditions, but there is no good scientific evidence to support these other uses.
When taken by mouth: Thiamine is commonly consumed in the diet and is likely safe when taken in appropriate amounts.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Thiamine is likely safe when taken by mouth as part of the diet. There isn't enough reliable information to know if higher doses are safe to use when pregnant and breast-feeding.

Children: Thiamine is likely safe when taken by mouth as part of the diet. There isn't enough reliable information to know if higher doses are safe or what the side effects might be.

Alcohol use disorder: People with alcohol use disorder often have low levels of thiamine and might need thiamine supplements. Nerve pain from alcohol use disorder can be worsened when thiamine levels are low.

Hemodialysis: People undergoing hemodialysis treatments might have low levels of thiamine and might need thiamine supplements.

Liver disease: People with chronic liver disease often have low levels of thiamine and might need thiamine supplements.


NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
  • Thiamine deficiency. Taking thiamine by mouth helps prevent and treat thiamine deficiency.
  • A brain disorder caused by low levels of thiamine (Wernicke-Korsakoff syndrome). Taking thiamine by IV helps decrease the risk and symptoms of Wernicke-Korsakoff syndrome (WKS), which is related to low levels of thiamine. It is often seen in people with alcohol use disorder. IV products can only be given by a healthcare provider.
Likely effective Effectiveness definitions
Possibly effective Effectiveness definitions
  • Menstrual cramps (dysmenorrhea). Taking thiamine by mouth seems to reduce menstrual pain in teenagers and young females.
Likely ineffective Effectiveness definitions
Possibly ineffective Effectiveness definitions
  • Surgery to improve blood flow to the heart (CABG surgery). Giving thiamine by IV before and after CABG surgery doesn't improve surgery outcomes. IV products can only be given by a healthcare provider.
  • Heart failure. Giving thiamine by IV or taking thiamine by mouth doesn’t seem to reduce the risk of dying or improve heart function in people with heart failure.
  • Mosquito repellent. Taking thiamine by mouth doesn't help to repel mosquitos.
  • Blood infection (sepsis). Giving thiamine by IV, or taking thiamine orally, alone or with vitamin C and the drug hydrocortisone, does not reduce the risk of dying or duration of hospital stay in people with sepsis. IV products can only be given by a healthcare provider.
There is interest in using thiamine for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.
Insufficient evidence Effectiveness definitions

Dosing & administration

Thiamine is an important nutrient. It's found in many foods, including cereal grains, beans, nuts, and meat.

The amount that should be consumed on a daily basis is called the recommended dietary allowance (RDA). For adult males, the RDA is 1.2 mg daily. For adult females 18 years of age, the RDA is 1 mg daily. For adult females 19 years and older, the RDA is 1.1 mg daily. The RDA during pregnancy and breastfeeding is 1.4 mg daily. Recommended amounts for children depend on age. Speak with a healthcare provider to find out what dose might be best for a specific condition.

Interactions with pharmaceuticals

Trimethoprim (Proloprim)

Interaction Rating=Minor Be watchful with this combination.

Thiamine is moved in and out of cells by pumps. Trimethoprim might change how these pumps work and increase how much thiamine stays in the body. In some cases, this might change the effects and side effects of thiamine.

Interactions with herbs & supplements

Betel Nut: Betel nuts change thiamine so it doesn't work as well. Regular, long-term chewing of betel nuts may contribute to thiamine deficiency.
Horsetail: Horsetail contains a chemical that can destroy thiamine in the stomach, possibly leading to thiamine deficiency. The Canadian government requires that horse chestnut products be certified as free of this chemical. Stay on the safe side, and don't use horsetail if you are at risk for thiamine deficiency.

Interactions with foods

Eating certain foods might reduce how much thiamine the body can absorb, which could lead to thiamine deficiency. Tannin-containing foods and beverages, such as coffee and tea, might have this effect. But you would need to consume a very large amount every day to cause deficiency. People who consume normal amounts of thiamine and vitamin C in the diet should not have this issue.

Eating a lot of raw fish or shellfish can also contribute to thiamine deficiency. But cooked fish and seafood aren't a problem. They don't have any effect on thiamine, since cooking destroys the chemicals that harm thiamine.
5.0 (2)
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Per tablet:
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5.0 (1 prac)
5.0 (1 client)
Practitioner product
Tresos Activated B PluSe
4.7 (11 pracs)
4.8 (28 clients)
Per tablet:
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GenoMulti Active B
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This monograph was last reviewed on 19/02/2024 11:00:00 and last updated on 16/04/2022 07:46:35. Monographs are reviewed and/or updated multiple times per month and at least once per year.
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