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Vitamin B12

Used for:Vitamin B12 deficiency, Peripheral neuropathy
Chinese name:

What is Vitamin B12 for?

Vitamin B12 is a water-soluble vitamin that is important for our metabolic functions and the normal functioning of nerves and blood cells. Cyanocobalamin is a man-made Vitamin B12 that can be used to treat Vitamin B12 deficiency due to inadequate dietary intake. Vitamin B12 deficiency often occurs in patients with malabsorption or metabolic disorders and who follow a strict vegetarian diet, which may lead to megaloblastic anemia and brain damage.

How to use it?

Vitamin B12 can be taken by mouth or intramuscular injection. 


If you are taking it by mouth, the dose can range from 50-2000 micrograms daily. Higher doses (i.e. 1000-2000 micrograms) by mouth are used for people with problems absorbing Vitamin B12. 


If you are taking it by intramuscular injection, you should start with 1 mg every 2-3 days for 11 doses and then 1 mg every month.

What are the side effects of Vitamin B12?

Vitamin B12 has no potential side effects. If you experience side effects, tell your doctor or pharmacist immediately.

Who should not take Vitamin B12?

  • People who are allergic to or hypersensitive to Vitamin B12, cobalt, or any component of the preparation.

Pharmacist Tips:

  • It is always highly recommended to get nutrients like Vitamin B12 from natural sources first. Food rich in Vitamin B12 is beef, eggs, clams, milk, etc.
  • Vitamin B12 is generally present in animal products. Vegan diets may result in Vitamin B12 deficiency and supplements are often needed. Pay attention to the amount of Vitamin B12 in different products as it can vary.

Common dosing schedule: 

  • Vitamin B12 can be taken with or without food. Long-term (more than 2 weeks) heavy alcohol consumption may reduce Vitamin B12 absorption.

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


Some common medications Vitamin B12 may interact with:

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

Where to buy Vitamin B12 in Hong Kong?

In Hong Kong, oral Vitamin B12 is an over-the-counter medicine which can be purchased without a prescription from any retail outlet in Hong Kong. This includes grocery stores, convenience stores, medicine shops, and pharmacies. It can also be obtained from doctors.


On the other hand, injectable Vitamin B12 is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It 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 https://www.drugoffice.gov.hk

Need more information?

For detailed information about the use of Vitamin B12 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.

Available dosage
  • 500mcg (Tablets)
  • 500mcg/ml (Injections)
Drug class
Sub class
Vitamins (Water Soluble)
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