* if patient with BMI above 25kg/m2 - start metformin
* if patient with BMI 25kg/m2 or less - consider starting metformin or prescribe an insulin secretagogue (sulphonylurea)
Consider the following when starting metformin [6,7]:
* step up metformin over several weeks to minimise risk of gastrointestinal (GI) side effects
* consider trial of extended-absorption metformin if GI tolerability prevents the person continuing with metformin
* review metformin dose if serum creatinine is greater than 130micromol/L or estimated glomerular filtration rate (eGFR) is less than 45mL/minute/1.73m2
* stop metformin if serum creatinine is more than 150micromol/L or the eGFR is less than 30mL/minute/1.73m2
* prescribe metformin with caution for those at risk of a sudden deterioration in kidney function, and those at risk of eGFR falling to less than 45mL/minute/1.73m2
* if the patient has mild to moderate liver dysfunction or cardiac impairment, discuss benefits of metformin so due consideration can be given to its cardiovascular-protective effects before any decision is made to reduce the dose
Consider sulphonylurea if [6,7]:
* patient is not overweight (tailor the assessment of body-weight-associated risk according to ethnic group); or
* metformin is not tolerated or is contraindicated; or
* a rapid therapeutic response is required due to hyperglycaemic symptoms
References:
[6] National Institute for Health and Clinical Excellence (NICE). Type 2 diabetes: newer agents. Clinical Guideline 87. London: NICE; 2009.
[7] Srinivasan B, Lawrence I, Davies M. Diabetes: glycaemic control in type 2. Clin Evid 2008; 07: 607.