Medicines & Supplements A to Z > Vitamin B1

Vitamin B1

Last updated on 17/09/2021.

Overview   |   Dosage   |    Side Effects   |   Precautions  |   Tips  |   Where To Buy  

GENERIC NAMES: Vitamin B1, Thiamine 



AVAILABLE DOSAGE FORMS: 100mg, 300mg (capsules)

What is Vitamin B1 for?

Vitamin B1 is a vitamin that can convert the food you eat into energy. It is therefore very important for the proper functioning of your body. Vitamin B1 supplement is needed to treat those who have Vitamin B1 / Thiamine deficiency or to prevent deficiency. The injection forms of Vitamin B1 can be used to treat Wernicke-Korsakoff syndrome, which is a brain disorder caused by insufficient Vitamin B1 in people who consume alcohol Thiamine deficiency can be caused by chronic dieting, alcoholism, and diets that mainly include highly processed foods. Some symptoms of thiamine deficiency include:

  • Irritability
  • Depression
  • Memory loss
  • Muscular weakness
  • Rapid heart rate
  • Fatigue

How to use it?

Vitamin B1 can be taken by mouth or by injection. 

If you are taking it for Vitamin B1 deficiency, usual doses range from 1.5-100 mg daily by mouth in mild cases or 200-300 mg daily in divided doses by mouth in severe cases. 

If you are taking it for Wernicke-Korsakoff syndrome, your doctor would start with 100-500 mg by intravenous injection, followed by maintenance dosing of 100 mg daily by injection. Chronic supplementation of Vitamin B1 is by mouth.

What are the side effects of Vitamin B1?

Vitamin B1 is water-soluble and accumulation in the body is unlikely. It  has no potential side effects. If you experience side effects, tell you doctor or pharmacist immediately.

Who should not take Vitamin B1?

Patients allergic to any component of the formulation.

Pharmacist Tips:

– Although you should obtain enough vitamin B from diet, your body may require supplementation if you are over 50 years old, are pregnant, or are eating a vegetarian/vegan diet.
– It is always best to consult your doctor or pharmacist before starting any supplement, especially if you already take medication, have health concerns, or are pregnant.
– Most people should get enough vitamin B in a healthy diet. Various food sources derived from vitamins, such as milk and products, meat, life, shells, fruits and vegetables, grains, nuts, beans and legume products.

Common dosing schedule:
Please refer to specific product instructions.

This schedule is for reference only, adjustments may be made according to individual needs. 

Some common medications Vitamin B1 may interact with:
– Antacids

Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Vitamin B1 in Hong Kong?

In Hong Kong, many types of Vitamin B1 are over-the-counter medicines and can be purchased without a prescription from any retail outlet in Hong Kong. This includes grocery stores, convenience stores, medicine shops, and pharmacies. The injection form of Vitamin B1 is a prescription only medicine and requires a prescription from a doctor to be purchased in a pharmacy. Vitamin B1 can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.

For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at

For detailed information about the use of Vitamin B1 in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.