Biguanides

Metformin (Glucophage, Glucophage XR) is the generic name of this drug. It works by inhibiting the production and release of glucose from your liver. It also lowers down the insulin secretion. One good thing about biguanides drug is that it tends to low down weight gain than do others. It can also improve blood cholesterol level, which is generally high if you are type 2 diabetic.

Side Effects:

If you already have a kidney problem, metformin may build up in your body. Inform your doctor when you are placed on this medication regarding your kidney problem.
If you are vomiting, have diarrhea, and can't drink enough fluids, you may need to stop taking this diabetes medication for a few days.
You may feel metallic taste.
If you are going for medical test using dye, or planning to opt for any surgery, then inform your doctor about your metformin intake. He will instruct you to stop taking metformin for some specific period.