Medicines & Supplements A to Z > Vitamin D2

Vitamin D2

Last updated on 16/07/2021.

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

GENERIC NAME: Ergocalciferol / Vitamin D2

CHINESE NAME: 麥角鈣化醇 / 維他命D2


DRUG CLASS: Vitamins

SUB CLASS: Vitamins (fat soluble), Vitamin D analogue

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

What is Vitamin D2 for?

Vitamin D is a fat-soluble vitamin that promotes calcium absorption, regulates bone growth, and facilitates immunological functions. In the Vitamin D family, Vitamin D2 and Vitamin D3 are most commonly found in your diet. While both types help you reach your daily Vitamin D requirements, they differ in several ways. Vitamin D2 mainly comes from plant sources and fortified foods, while Vitamin D3 is only found in animal sources. Research also suggests that Vitamin D2 is less easily absorbed by the body than Vitamin D3. 

Your body cannot get adequate amounts of Vitamin D from diet alone. Instead, your skin produces most of the Vitamin D your body requires when exposed to sunlight. Vitamin D deficiency is usually observed in people with limited sunlight exposure or with a diet that is deficient in Vitamin D. Vitamin D deficiency can be prevented and reversed by taking oral supplements of ergocalciferol (Vitamin D2) or cholecalciferol (Vitamin D3) on a daily basis for months.

How to use it?

Vitamin D2 is available as oral preparations. If you are using it for the prevention of Vitamin D deficiency, you can take 400 units daily. If you are using it for the treatment of Vitamin D deficiency, you can take 800 units daily. For severe deficiency, higher doses may be required.

What are the side effects of Vitamin D2?

Vitamin D2 is generally safe to use. However, abdominal pain, headache, high calcium level in blood or urine, and/or nausea may occasionally occur.

Who should not take Vitamin D2?

– Anyone who has an increased calcium level in blood
– Anyone who has metastatic calcification

Pharmacist Tips:

– It is always highly recommended to get nutrients like Vitamin D from natural sources first, such as salmon, foods fortified with Vitamin D, and egg yolk. Vitamin D is also produced by sunlight exposure.
– Pay attention to the amount of Vitamin D in different products as it can vary. Taking too much Vitamin D may lead to Vitamin D toxicity. You may experience symptoms such as nausea, vomiting, and sweating.
– 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.
– Many food sources contain Vitamin D. Vitamin D2 mostly comes from plant sources such as mushrooms. Vitamin D3 comes from animal sources including oily fish and fish oil (salmon, sardines, tuna), egg yolk, cheese and liver.
– Apart from diet, your skin produces Vitamin D when exposed to sunlight. Note that your body cannot make enough Vitamin D if you stay indoors by a sunny window, as ultraviolet B (UVB), the light which triggers Vitamin D3 formation in the skin, may be filtered.

Common dosing schedule:
Vitamin D2 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 D2 may interact with:
Aluminium hydroxide
– Bile acid sequestrants, e.g. Cholestyramine
– Thiazide diuretics, e.g. Hydrochlorothiazide

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

Where to buy Vitamin D2 in Hong Kong?

In Hong Kong, Vitamin D2 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 D2 (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.