Medicines & Supplements A to Z > Vitamin K

Vitamin K

Last updated on 16/07/2021.

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



BRAND NAME(S) IN HONG KONG: Doctor’s Best, Now Foods

DRUG CLASS: Vitamins

SUB CLASS: Vitamins (fat soluble)

USED FOR: Nutritional supplementation, prevention and treatment of Vitamin K deficiency

AVAILABLE DOSAGE FORMS: 45mcg (capsules)

What is Vitamin K for?

Vitamin K is a family of fat-soluble vitamins that activate proteins which helps blood clotting, wound healing and bone growth. The two main forms of Vitamin K found in our diet are Vitamin K1 (Phylloquinone) and Vitamin K2 (Menaquinone). Vitamin K1 primarily comes from plant sources of leafy green vegetables. It makes up about 75-90% of all Vitamin K we consume. Vitamin K2 is found in fermented foods and animal products, and is also produced by gut bacteria. There are several subtypes of Vitamin K2, named by the length of their side chains, ranging from menaquinone MK-4 to MK-13.

Most people can obtain enough Vitamin K by eating a balanced diet, however in some individuals it is still possible to be deficient. People who take medications that block Vitamin K metabolism such as antibiotics, or those with conditions that cause malabsorption of food and nutrients are more prone to Vitamin K deficiency. Signs and symptoms of vitamin K deficiency include longer time for blood to clot, bleeding, haemorrhaging, and osteoporosis.

How to use it?

Vitamin K is available as oral preparations. For specific dosages, please refer to specific product labels.

Healthy children and adults do not need supplements as they can obtain enough from a normal diet. However, people with Vitamin K deficiency may take Vitamin K supplements. Adults need approximately 1 mcg per body weight of Vitamin K each day. The recommended adequate intake for vitamin K is based only on vitamin K1 and is set at 90 mcg daily for adult women and 120 mcg daily for adult men.

What are the side effects of Vitamin K?

Vitamin K is generally safe to use. However, some people may experience stomach discomfort or diarrhoea.

Who should not take Vitamin K?

Patients allergic to any component of the formulation.

Pharmacist Tips:

– It is always highly recommended to get nutrients like Vitamin K from natural sources first, such as leafy green vegetables.
– Since Vitamin K is fat-soluble, you may eat Vitamin K foods with some fat to improve absorption. For example, you may add olive oil or diced avocado in a leafy green salad.
– Chew the tablets before swallowing for chewable preparations.
– 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.
– Vitamin K is primarily found in leafy green vegetables and vegetable oils, while small amounts are found in meat and dairy foods. Vitamin K1 mostly comes from plant sources, especially leafy green vegetables like spinach, broccoli and lettuce. Vitamin K2 comes from fermented food such as Japanese Natto and hard cheese, and animal sources including eggs, liver and organ meats, beef, pork and chicken.

Common dosing schedule:
Vitamin K can be taken with or without meals. Please refer to specific product instructions.

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

Some common medications Vitamin K may interact with:
– Antibiotics
– Bile acid sequestrants, e.g. Cholestyramine

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

Where to buy Vitamin K in Hong Kong?

In Hong Kong, Vitamin K is an over-the-counter medicine and 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. 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

Need more information?

For detailed information about the use of Vitamin K (supplement) 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.