> Western Medicines > Metformin

What is Metformin for?

Metformin is the first-line medication for the treatment of type 2 diabetes mellitus. It can also be used for polycystic ovary syndrome.

How to use it?

The dose of Metformin is gradually increased over time in order to avoid stomach related side effects such as stomach pain and diarrhea. You should initiate Metformin at a low dose (250 to 500 mg once daily) and gradually increase the dose as discussed with your doctor or pharmacist. Standard immediate release Metformin is usually taken 2 or 3 times daily. The extended release (XR), modified release (MR), sustained release (SR or retard) formulations of Metformin release the drug more slowly and are more conveniently dosed 1 time per day.


For Type 2 diabetes mellitus

Orally using immediate-release medicines


Start with 500 mg once daily with breakfast for at least a week, followed by 500 mg twice daily with breakfast and dinner for at least a week, and then 500 mg 3 times daily with breakfast, lunch and dinner; The maximum daily dose is 2g.


Orally using modified-release medicines


Start with 500 mg once daily with dinner, increase gradually every 10-15 days if necessary up to 2 g once daily with dinner. If you glucose level cannot be controlled with this regimen, you may increase the dose to twice daily with meals. If it still fails, you may change to the immediate-release medicines.


For polycystic ovary syndrome

Orally using immediate-release medicines


Start with 500 mg once daily with breakfast for a week, followed by 500 mg twice daily with breakfast and dinner for a week, then 1.5-1.7 g daily in 2-3 divided doses.

What are the side effects of Metformin?

Common side effects of Metformin include abdominal pain, decreased appetite, transient diarrhoea, gastrointestinal disorder, nausea and vomiting, and altered taste.

Who should not take Metformin?

  • People who are allergic to Metformin or any ingredient of the formulation
  • People with acute or chronic metabolic acidosis

Pharmacist Tips:

  • Avoid heavy consumption of alcohol while you are taking Metformin.
  • Non-drug management, including diet and exercise, also plays an important role in controlling diabetes
  • Tell your doctor or pharmacist if you have symptoms of low blood sugar level, such as sweating, feeling dizzy, fast heartbeat, and pale skin.
  • Always carry a fast-acting carbohydrate with you, such as sweets, in case of a low blood sugar level.

Common dosing schedule:
Take Metformin with or after a meal to decrease gastrointestinal discomfort.


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


Some common medications Metformin may interact with:

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

Where to buy Metformin in Hong Kong?

In Hong Kong, Metformin 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 Metformin 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
Available dosage
  • 500mg / 750mg (Prolonged-Release Tablets)
  • 500mg / 850mgl1000mg (Tablets)
Drug class
Antidiabetic Drugs
Sub class
Other drugs in same class