Severe side effects of taking Metformin drug prescribed to 120 million people worldwide

Said to be prescribed to over 120 million people around the globe, metformin is also commonly dropped by patients.

The medicine is used primarily to treat type 2 diabetes and gestational diabetes as well as being used to help prevent type 2 diabetes by those at high risk of developing it.

In some cases, it is also used to improve fertility for those with polycystic ovary syndrome (PDCOS).

Metformin works by improving the way the body handles insulin in order to lower blood sugar levels. The NHS adds that even for those without diabetes, the drug can therefore improve ovulation and encourage regular periods.

While it does not cause weight gain like some other medicines for diabetes, metformin carries a number of side effects – just as most medications do. And it’s thought that the toll it takes on the digestive system puts many people off.

The medicine helps the insulin you produce work better. (Scott Olson/Getty Images)

Common side effects

Both the NHS and Diabetes UK stress the importance of taking metformin with food to help with any nausea the medicine may cause.

The medicine may also cause vomiting, diarrhoea, stomach ache, loss of appetite and a metallic taste in the mouth.

A more longer-term side effect of metformin (particularly for those on a high dose) is lower levels of vitamin B12 (this vitamin helps keep red blood cells and nerves healthy).

Symptoms of this deficiency include new or much worse extreme tiredness, mouth ulcers, vision problems, pins and needles, a red and sore tongue and pale or yellow skin.

Doctors can check your B12 serum levels and you should call your GP or 111 if you experience this.

Metformin doesn’t usually cause blood sugar levels to get too low but hypos can happen when its taken with other diabetes medications. So, it’s important to have regular meals and carry a fast-acting carbohydrate with you.

It's typically used to treat type-2 diabetes. (Joan Slatkin/Education Images/Universal Images Group via Getty Images)

Severe side effects

The more serious side effects are rare but they can happen.

If you are taking metformin and get a general feeling of being unwell with severe tiredness, fast or shallow breathing, being cold and a slow heartbeat, you must call your doctor or 111 straight away.

The same goes if the whites of your eyes or your skin turns yellow as this can be a sign of liver problems.

And in rare cases, some patients may have a serious allergic reaction to the medicine. You should call 999 if you display signs of anaphylaxis such as your lips, mouth, tongue or throat becoming suddenly swollen or struggles breathing.

Always seek advice from a healthcare professional if you have any concerns.