There is inadequate evidence to make a recommendation about the use of metformin for irregular menstrual cycles. Any efficacy in regularising menstruation usually takes at least 5 months. Weight loss has proved more efficient than metformin in restoring menstrual regularity.
The latest PCOS guidelines make the following recommendations regarding the use of metformin for non-conceptional indications:
Metformin in addition to lifestyle, should be considered in adult women with PCOS with BMI ≥ 25kg/m2 for management of weight and metabolic outcomes.
Metformin in additional to lifestyle, could be considered in adolescents with a clear diagnosis of PCOS or with symptoms of PCOS before the diagnosis is made.
Metformin may offer greater benefit in high metabolic risk groups including those with diabetes risk factors, impaired glucose tolerance or high-risk ethnic groups.