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Metformin is a prescription medication primarily used to control high blood sugar in people with type 2 diabetes.

Last Modified: 09 May 2024

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What is Metformin? 

Metformin is a prescription medication primarily used to control high blood sugar in people with type 2 diabetes. 

Metformin's active ingredient is metformin hydrochloride. It may also contain inactive ingredients to form the tablet or extended-release tablet. 

Metformin is a biguanide and is composed of two linked guanidine rings. It is synthesized in a laboratory setting and is not derived from any natural sources. 

Global Name

Generic name: Metformin
Brand names:  Glucophage, Metformin ER, Glumetza, Fortamet, Riomet


What is Metformin used for? 

Metformin is used to improve blood sugar control in adults and children with type 2 diabetes. It is also used in polycystic ovary syndrome (PCOS) and, less commonly, for the prevention of type 2 diabetes. 

How do you use Metformin? 


Metformin is available in tablet, extended-release tablet, and liquid forms. 

Dosage information:

  • Adults: Start with 500 mg orally twice a day or 850 mg once a day, with gradual dose increases to reduce gastrointestinal side effects. 
  • Children (10 years and older): Initial dose typically 500 mg orally twice a day. 


  • Children: Yes, for those 10 years and older. 
  • Adults: Yes. 
  • Elderlies: Yes, with consideration for renal function. 
  • Pregnancy and Lactation: Consult a healthcare provider; may be used in some cases under medical supervision, generally safe in pregnancy (FDA Category B)  

Is there anyone who can’t take Metformin? 

  • Children: Not recommended for children under 10 years. 
  • Adults: Those with severe kidney or liver problems should not take it. 
  • Elderlies:  Elderly with compromised renal function are at-risk for lactic acidosis therefore use is generally avoided. 
  • Allergy to metformin or any other components of the drug.

Warnings and Precautions:

Monitor blood sugar levels regularly, take after meals to reduce gastrointestinal upset, and watch for signs of lactic acidosis, a rare but serious complication. 

Drug and Food/Beverage Interactions

Metformin should not be used with iodinated contrast media or with medications that can affect renal function. Can have additive hypoglycemic effect when used with insulin and other anti-diabetes medication. High-fat and high-calorie diet can lower the absorption of metformin from the intestines. Alcohol should be avoided due to the risk of lactic acidosis. 


Side Effects

Common side effects include gastrointestinal issues such as diarrhea, nausea, and abdominal pain. Lactic acidosis is a severe but rare side effect. 

Pharmacist Tips

Storage information:  

  • Gradual Introduction: Start Metformin at the lowest dose and gradually increase as directed by your healthcare provider to minimize gastrointestinal side effects. 
  • Timing of Doses: Take Metformin with meals to help reduce stomach upset. If you’re on an extended-release formula, remember to take it with your evening meal. 
  • Maintain Diet and Exercise: For the best glucose control, maintain a diet low in sugars and refined carbs and follow a regular exercise routine, as advised by your healthcare provider. 
  • Understanding Side Effects: If you experience minor side effects, such as gastrointestinal discomfort, these may decrease over time. However, if you experience symptoms like muscle pain, difficulty breathing, stomach pain with nausea, or any unusual symptoms, contact your doctor immediately as these could be signs of lactic acidosis. 
  • Missed Dose Protocol: If you miss a dose, take it as soon as you remember unless it’s almost time for your next dose. Do not double up on doses to make up for the missed one. 
  • Traveling with Medication: When traveling, keep Metformin in its original container, labeled by the pharmacy, and always carry it in your carry-on baggage. 
  • Regular Blood Sugar Testing: Keep track of your blood sugar levels as your doctor has instructed. This will help you determine how well Metformin is working for you. 
  • Kidney Function Monitoring: Since Metformin is cleared by the kidneys, it's essential to have your kidney function checked before starting the medication and regularly thereafter. 
  • Proper Disposal: Do not flush unused or expired Metformin down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed by bringing it to a take-back program if available. 
  • Consult Before Adding Supplements: Some vitamins and herbal supplements may interact with Metformin. Always consult with your healthcare provider before starting any new supplements. 
  • Stay Hydrated: Drinking plenty of fluids may help prevent some of the side effects associated with Metformin, such as headaches and dehydration. 


Where is Metformin available in Hong Kong?

Metformin is a prescription medication that can be prescribed by healthcare providers then bought in pharmacies. 



Is Metformin safe for long-term use?

Metformin is generally safe for long-term use under medical supervision.

Can Metformin cause weight loss?

Metformin is not a weight loss drug, but it may lead to modest weight loss in some people. 

Is Metformin available for purchase over the counter?

No, Metformin requires a prescription from a healthcare professional.

How fast does Metformin work?

Metformin typically starts working within a few hours of taking the medication, but its full effects may take several weeks to manifest. The medication works by reducing the production and release of glucose from the liver, improving insulin sensitivity, and helping the body use insulin more effectively. 

This website provides content related to drug use and medicine for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Do not use the information on this website to diagnose or treat a health problem or disease without consulting a qualified healthcare provider. The website's owners and contributors are not liable for any repercussions, adverse effects, or consequences resulting from the use of any medication or information provided herein.

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