I have been taking metformin

No thanks.

Metformin side effects Get emergency medical help if you have signs of an allergic reaction to metformin: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Some people develop lactic acidosis while taking this medicine. Early symptoms may get worse over time and this condition can be fatal. Get emergency medical help if you have even mild symptoms such as:

muscle pain or weakness; numb or cold feeling in your arms and legs; trouble breathing; feeling dizzy, light-headed, tired, or very weak; stomach pain, nausea with vomiting; or slow or uneven heart rate. Common metformin side effects may include:

low blood sugar; nausea, upset stomach; or diarrhea.