Reviewed on 8/17/2021

What Is Thiamine and How Does It Work?

Thiamine is a prescription and over-the-counter (OTC) vitamin, also called vitamin B1. Vitamin B1 is found in many foods including yeast, cereal grains, beans, nuts, and meat. It is often used in combination with other B vitamins.

Thiamine is taken for conditions related to low levels of thiamine, including beriberi and inflammation of the nerves (neuritis) associated with pellagra or pregnancy. Thiamine is also used for digestive problems including poor appetite, ulcerative colitis, and ongoing diarrhea.

Thiamine is also used for AIDS and boosting the immune system, diabetic pain, heart disease, alcoholism, aging, a type of brain damage called cerebellar syndrome, canker sores, vision problems such as cataracts, and glaucoma, motion sickness, and improving athletic performance. Other uses include preventing cervical cancer and progression of kidney disease in patients with type 2 diabetes.

Some people use thiamine for maintaining a positive mental attitude; enhancing learning abilities; increasing energy; fighting stress; and preventing memory loss, including Alzheimer's disease.

Healthcare providers give thiamine shots for a memory disorder called Wernicke's encephalopathy syndrome, other thiamine deficiency syndromes in critically ill people, alcohol withdrawal, and coma.

Thiamine is available under the following different brand names: vitamin B1.

What Are Dosages of Thiamine?

Dosages of Thiamine:

Adults and Pediatric Dosages


  • 50 mg
  • 100 mg
  • 250 mg


  • 50 mg

Injectable solution

  • 100 mg/ml

Dosage Considerations – Should be Given as Follows:

Recommended Daily Average


  • Males: 1.2 mg/day
  • Females: 1.1 mg/day
  • Pregnancy/Lactation: 1.4 mg/day


  • Infants 0-6 months: 0.2 mg/day
  • Infants 6-12 months: 0.3 mg/day
  • Children 1-3 years old: 0.5 mg/day
  • Children 3-8 years old: 0.6 mg/day
  • Children 8-13 years old: 0.9 mg/day
  • Children 13-18 years old: 1.2 mg/day (male), 1 mg/day (female)


  • 10-50 mg/day orally in divided doses



  • Intramuscularly: 5-30 g three times daily (if critically ill); then 5-30 mg three times daily for 1 month
  • Duration dependent on the persistence of symptoms


  • 10-25 mg intravenously/intramuscularly per day (if critically ill) or 10-50 mg dose orally per day for at least 2 weeks, then 5-10 mg/day orally for 1 month
  • Duration dependent on the persistence of symptoms

Wernicke Encephalopathy

  • 100 mg intravenously; then 50-100 mg/day intramuscularly or intravenously until consuming a regular balanced diet

Thiamin Deficiency

  • 1 tablet or capsule/day
  • The need for thiamin increased when the carbohydrate content of the diet is high


Next to red peppers, you can get the most vitamin C from ________________. See Answer

What Are Side Effects Associated with Using Thiamine?

Side effects of thiamine include:

  • warmth
  • severe allergic reaction (anaphylaxis)
  • skin discoloration
  • sweating
  • restlessness
  • rapid swelling of the skin
  • itching
  • hives
  • fluid in the lungs (pulmonary edema)
  • weakness
  • tightness of the throat
  • nausea

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Thiamine?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Thiamine has no known severe interactions with other drugs.
  • Thiamine has no known serious interactions with other drugs.

Moderate interactions of thiamine include:

Thiamine has mild interactions with at least 69 different drugs.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

What Are Warnings and Precautions for Thiamine?


  • This medication contains thiamine. Do not take vitamin B1 if you are allergic to thiamine or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


  • Hypersensitivity

Effects of Drug Abuse

  • No information available

Short-Term Effects

  • See "What Are Side Effects Associated with Using Thiamine?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Thiamine?"


  • In pregnancy (doses exceeding the recommended daily average)
  • Acute thiamine deficiency reported with dextrose administration; use caution when thiamine status uncertain
  • Hypersensitivity reactions reported following repeated parenteral doses
  • Parenteral production may contain aluminum; use caution in patients with impaired kidney (renal) function
  • Evaluate for additional vitamin deficiencies if patient diagnosed with thiamin deficiency; single vitamin deficiencies are rare

Pregnancy and Lactation

  • Thiamine (injectable) is generally acceptable during pregnancy
  • Controlled studies in pregnant women show no evidence of fetal risk
  • Only use thiamine in doses exceeding the recommended daily average during pregnancy with caution if benefits outweigh risks
  • Animal studies show risk and human studies are not available, or neither animal nor human studies were done
  • Thiamine is safe to use while breastfeeding


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Medscape. Thiamine.
RxList. Vitamin B1.

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