Metformin is a biguanide and is the only one in this class registered for use for Australia.  

Metformin is an insulin sensitiser and does not cause hypoglycaemia as a side effect. It is one of the few diabetes medicines that will continued to be prescribed once insulin is initiated to keep the prescribed dose of insulin as low as practicable. 

  • Immediate Release: prescribed up to three times a day   
  • Modified Release: (MR) or sustained release (SR) prescribed once or twice daily 
  • Metformin lowers blood glucose levels mainly by reducing gluconeogenesis (the production of glucose from non-carbohydrate carbon substrates) in the liver and as a result reduces the level of glucose in the blood.
  •  Metformin also makes the body more able to absorb glucose in the blood (reduces insulin resistance).  
  • Metformin does not stimulate the production of  more insulin and so does not cause hypoglycaemia as a side effect. 
  • All doses of metformin should be taken with food and never on an empty stomach since it is known for causing gastrointestinal side effects including nausea, bloating and diarrhoea. Sometimes however it may also cause constipation.  
  • It is also known for causing intermittent diarrhoea which people may put down to something they have eaten especially when eating out and when they have limited control over their food intake (i.e., at a friend’s house for a meal).