Thiamine at a glance
Medicine class
Vitamin B1 replacement.
Main role
Prevention or treatment of thiamine deficiency, depending on the formulation.
Available routes
Oral tablets and an injection given into a muscle or vein by a healthcare professional.
Food
Tablets can be taken with or without food. Food may help if they cause stomach upset.
What is Thiamine used for?
The selected UK products are licensed for:
Oral tablets: treatment of thiamine deficiency.
Injection: prevention and treatment of vitamin B1 deficiency, including beriberi, deficiency associated with chronic alcohol use and Wernicke–Korsakoff syndrome.
How does Thiamine work?
The body converts thiamine into an active coenzyme needed to release energy from carbohydrates. Replacing deficient thiamine supports normal cellular metabolism, particularly in the nervous and cardiovascular systems.
Thiamine preparations and strengths
Tablet
Route: Oral
Strengths: 50 mg, 100 mg
Injection
Route: Parenteral
Strengths: 50 mg/mL, 125 mg/mL
How to take Thiamine
Follow the prescription or pack instructions. Swallow tablets with water, with or without food. The selected tablet's break line makes it easier to swallow but does not produce equal portions. A healthcare professional gives the injection into a muscle or slowly into a vein.
Tell the healthcare team about previous reactions to thiamine before an injection.
Check other vitamin or mineral supplements because they may already contain thiamine.
Thiamine side effects
Common or expected effects
- Feeling sick or vomiting
- Diarrhoea
- Abdominal pain or stomach upset
- Pain or burning at the injection site
Get urgent medical advice
- Severe allergic reaction, including facial or throat swelling, breathing difficulty, rapid heartbeat, collapse or shock
- Worsening injection-site inflammation or an allergic reaction following an injection
Thiamine in pregnancy
Thiamine can be used in pregnancy when recommended to correct or prevent deficiency. Product and route should be selected by the prescriber. The selected injection requires individual benefit–risk assessment, while the selected tablet should be used only under medical direction.
Thiamine while breastfeeding
Thiamine occurs naturally in breast milk and can usually be taken when recommended by a clinician. Product and route matter: information after high exposure to the selected injection is limited, and the selected tablets should be used only under medical direction.
Thiamine interactions
Thiamine has relatively few recognised medicine interactions, but the following may affect replacement or monitoring:
Fluorouracil and other fluoropyrimidines, such as capecitabine
These medicines may reduce thiamine's effect.
Ifosfamide
It may antagonise thiamine and contribute to deficiency.
Common questions about Thiamine
Answers are fully visible for fast scanning and source review.
Why is thiamine hydrochloride sometimes injected?
Injection may be chosen when thiamine must be restored rapidly or tablets are unsuitable because of vomiting, malabsorption or another clinical reason.
Can the selected tablet be split?
It may be broken along the score line to make swallowing easier, but the line is not intended to produce equal portions.
Does thiamine hydrochloride contain lactose?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.