What is Vitamin B1?

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.

Uses & Effectiveness?

Effective for

• 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.

Possibly Effective for

• Menstrual cramps (dysmenorrhea). Taking thiamine by mouth seems to reduce menstrual pain in teenagers and young females.

Possibly Ineffective for

• 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.
• Mosquito repellent. Taking thiamine by mouth doesn't help to repel mosquitos.
• Blood infection (sepsis). Giving thiamine by IV, 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.

Side Effects

When taken by mouth: Thiamine is commonly consumed in the diet and is likely safe when taken in appropriate amounts.

Special Precautions and Warnings

Pregnancy and breastfeeding: 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 breastfeeding.

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. The 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.