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Overview: Thiamine (vitamin B1) is commonly used to increase vitamin B1 levels and treat vitamin B1 deficiency. It is available in various forms, including as a prescription and as a dietary supplement. Thiamine is usually well tolerated. Before using thiamine, tell your health care provider about all of your health conditions and any medicines or supplements you may be using.

Uses

What is thiamine used for?

Thiamine (vitamin B1) is commonly used to prevent low vitamin B1 levels. It is also used to treat conditions caused by low vitamin B1 levels, including the following.

Thiamine may also be used for other conditions as determined by your health care provider.

Note: The FDA has not reviewed thiamine for safety and effectiveness. Learn more about dietary supplements here.

Vitamin B1 is also available in the form of benfotiamine, a synthetic substance that is made in a lab. See Benfotiamine for more information.

How does thiamine work (mechanism of action)?

Thiamine is vitamin B1. Your body uses this vitamin to produce energy and help your cells to grow and function properly.

In the United States, most people get enough vitamin B1 from their diet. It is found in grains, fish, meat, black beans, soybeans, seeds, and nuts. It is also found in many fortified cereals and breads. For most adults, the recommended daily intake of vitamin B1 is 1.1 to 1.2 milligrams (mg). But some people either do not get enough from their diet or have trouble absorbing it. When this happens, you can take thiamine to replace what you are not getting from your diet.

People who regularly consume large amounts of alcohol may have low levels of vitamin B1. This increases their risk of vitamin B1 deficiency (beriberi) and a serious brain and nerve problem called Wernicke-Korsakoff syndrome. Taking thiamine can help treat these conditions.

How is thiamine supplied (dosage forms)?

Brands and other names

  • Betalin S
  • Betamin

Example dosage forms and strengths

Thiamine, also known as vitamin B1, is available as a dietary supplement in various strengths and dosage forms. Thiamine is also found as an ingredient in some multivitamins, B-complex vitamins, or other supplements.

Thiamine is also available as a prescription in an injectable form that is given by a health care provider.

How should I store thiamine?

Thiamine products should be stored according to the product label. If you are not sure how to store your product, ask your pharmacist.

Side Effects

What are the most common side effects of thiamine?

Thiamine is usually well tolerated. Tell your health care provider if you have any side effects that bother you.

There may be side effects of thiamine that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of thiamine?

While less common, the most serious side effects of thiamine are described below, along with what to do if they happen.

Severe Allergic Reactions. Thiamine may cause allergic reactions, which can be serious. Stop using thiamine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown, depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use thiamine?

Allergies to Ingredients. People who are allergic to any of the following should not use thiamine.

  • Betalin S
  • Betamin
  • Thiamin
  • Thiamine
  • Vitamin B1
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific thiamine products they stock.

What should I know about thiamine before using it?

Thiamine dietary supplements are taken by mouth. Thiamine may also be given as an injection into your vein (intravenously, or IV) or muscle (intramuscularly, or IM) by a health care provider in a health care facility.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider. Do not take more than the recommended amount.

Keep thiamine out of the reach of children.

People who are over the age of 65 are more likely to have low thiamine levels. If you are in this age group, talk to your health care provider about whether you should use a thiamine dietary supplement.

The FDA has not tested thiamine dietary supplement products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using thiamine?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if thiamine is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have or have had any of the following.

Other Medicines and Supplements. Thiamine may interact with other medicines and supplements. Before taking thiamine, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should take thiamine while you are pregnant or trying to get pregnant.

Breastfeeding. Thiamine passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take thiamine while breastfeeding.

Interactions

Does thiamine interact with foods or drinks?

There are no known interactions between thiamine and foods or drinks.

It is unknown if drinking alcohol will affect thiamine, but drinking large amounts of alcohol may lower the levels of vitamin B1 in your body. It is best to limit the amount of alcohol you drink.

Does thiamine interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using thiamine.

  • Fluorouracil (5-FU), which is a type of chemotherapy used to treat cancer
  • Furosemide (Lasix), which is a type of diuretic, also called a water pill 

This may not be a complete list of medicines that can interact with thiamine. Always check with your health care provider.

Overdose/Missed Dose

What should I do if I accidentally use too much thiamine?

If you or someone else has used too much thiamine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of thiamine?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.