Biguanides are a class of drugs that are prescribed for patients with type 2 diabetes. These are oral medications and have antihyperglycemic properties. They are sometimes also prescribed for patients with type 1 diabetes in conjunction with insulin therapy. In people with type 2 diabetes, biguanide reduces blood sugar levels in two ways. First, they reduce the amount of glucose produced by the liver. Secondly, they assist in increasing the amount of glucose that is absorbed by the muscles of the body. This action is the reduction of insulin resistance. They are also known to reduce the LDL cholesterol levels and lower the HbA1c levels better than other diabetes medications. As such, biguanides do not act by affecting the intrinsic output of the insulin (as against other anti-diabetic medications). They increase the glucose uptake and reduce plasma glucose levels. People who are not able to control their blood sugar levels with modifications in diet and exercise are generally prescribed biguanides; however, these medications are not generally prescribed for those with low insulin levels as this might lead to liver and kidney damage. Also, people about to undergo a surgery in the near future are asked not to take this medication. A common biguanide that is available for patients with type 2 diabetes is metformin (See: Metformin). Metformin is available in a single form or in a combination. The common names for metformin in a single form include Glucophage and Glucophage XR. In a combination form, it comes in the form of metformin and glipizide, metformin and repaglinide, and metformin and rosiglitazone. Metformin is also known to induce weight loss. Some common side effects of biguanides and metformin include lactic acidosis, swelling of the tongue or face, muscle pain and weakness, trouble breathing, lightheadedness, stomach pain, nausea, vomiting, low sugar level, and diarrhea.