Metformin

Metformin is a medicine used to help control blood sugar levels. It is mainly used to treat type 2 diabetes, and it is sometimes used for diabetes in pregnancy, alongside insulin in type 1 diabetes, or to help with polycystic ovary syndrome [1].

It comes as standard and slow-release tablets, a liquid and a powder, and is available only on prescription [1].

• Metformin is usually taken with or just after food to reduce stomach side effects [1].
• Feeling sick or having diarrhoea is common at first and often settles within a couple of weeks [1].
• It is often needed long term, and doses are usually increased slowly [1].
• You will normally have regular blood tests to check how well it is working [1].

Metformin can be taken by most adults and by children aged 10 and over, but it does not suit everyone [1]. It may not be suitable if you have had an allergic reaction to it, have certain liver or kidney problems, a severe infection, uncontrolled heart failure, or drink a lot of alcohol [1]. Tell your prescriber about your health and any other medicines so they can check it is right for you [1].

Take metformin as your prescriber tells you and as set out on the label — standard tablets should be swallowed whole with water and not crushed or chewed [1]. It is usually taken with meals, and the dose depends on the person and the type of tablet [1]. If you miss a dose, skip it if your next one is due soon rather than doubling up [1]. Do not stop taking it without advice [1].

Common side effects can include feeling sick, being sick, diarrhoea, stomach ache and a loss of appetite, and these often improve as your body gets used to the medicine [1]. Long-term use can occasionally affect vitamin B12 levels [1]. Rarely, metformin can cause a serious problem called lactic acidosis — get urgent medical help if you feel very unwell with fast breathing, severe drowsiness or muscle pains [1].

Metformin can interact with some medicines, including water tablets (diuretics), steroids and some blood pressure medicines, and dehydration or certain scans using contrast dye can also affect it [1]. Tell a pharmacist or doctor what else you take, including over-the-counter and herbal products, before starting it [1].

Suspected side effects from metformin can be reported to the MHRA through the Yellow Card scheme, which helps monitor medicine safety in the UK [2]. Seek medical help for any serious reaction as well as reporting it.