> Western Medicines > Magnesium


Used for:Dietary supplementation, Constipation, Relief of heartburn and stomach discomfort
Chinese name:

What is Magnesium for?

Magnesium is commonly used in several forms in Hong Kong. Magnesium Hydroxide (often called milk of magnesia) is used as a laxative to treat constipation and as an antacid to treat dyspepsia (heartburn). In Hong Kong, it is often combined in products containing aluminum, and Simethicone or Dimethicone.

Other forms of Magnesium, such as Magnesium Sulphate are used to treat or prevent magnesium deficiency and to empty the bowel (as an enema).


Many people use non-prescription Magnesium supplements to improve their bone health, to prevent migraines, or for sleep. Magnesium is often included as an ingredient in multivitamins.

How to use it?

When Magnesium is used as an antacid, it can be taken up to four times per day. When taken as a laxative for occasional constipation, it can be used either once daily at bedtime or 2 times per day. For other uses, Magnesium can be taken once or twice daily.


Because of the wide variety of Magnesium products available, check with the specific product labelling for detailed dosage instructions.


Administration of Magnesium may need to be separated from the dosing time of your other medications to avoid drug interactions.

What are the side effects of Magnesium?

The most common side effect of oral Magnesium products is diarrhea. Products which also contain aluminum or calcium help reduce the chance of experiencing diarrhea. People with kidney problems should speak with their pharmacist or doctor before using Magnesium.

Who should not take Magnesium?

People who are allergic to or sensitive to any ingredient of the formulation.

Pharmacist Tips:

  • Drink an adequate amount of water (8 ounces) while using Magnesium.
  • Magnesium can cause a metallic taste in the mouth.

Common dosing schedule:
It is best to take Magnesium on an empty stomach.


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


Some common medications Magnesium may interact with:

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

Where to buy Magnesium in Hong Kong?

In Hong Kong, many types of Magnesium 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. They can also be obtained from doctors. The injection forms of Magnesium are prescription only medicines and require a prescription from a doctor to be purchased in a pharmacy or at a doctor’s clinic directly. 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 Magnesium 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.

Brands in Hong Kong
Milk of Magnesia
Maalox Plus
Available dosage
  • 20mg / 40mg (Capsules)
  • 20mg / 40mg (Delayed-Release Tablets)
Drug class
Sub class
Minerals & Electrolytes
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