[8] Common side effects include headaches, swelling of the legs, and upper respiratory tract infections.

[8] Serious side effects may include angioedema, low blood sugar, kidney problems, pancreatitis, and joint pain.

[17] The drugs are approved to improve blood sugar control in adults aged 18 and older with type 2 diabetes.

[17] Adverse effects from sitagliptin are similar to placebo, except for rare nausea, common cold-like symptoms, and photosensitivity.

[22] The existence of rare case reports of kidney failure and hypersensitivity reactions is noted in the United States prescribing information, but a causative role for sitagliptin has not been established.

[26] In 2015, the US Food and Drug Administration (FDA) added a new warning and precaution about the risk of "severe and disabling" joint pain to the labels of all DPP-4 inhibitor medicines.

[28] By preventing breakdown of GLP-1 and GIP, they are able to increase the secretion of insulin and suppress the release of glucagon by the alpha cells of the pancreas.

[medical citation needed] As the blood glucose level approaches normal, the amounts of insulin released and glucagon suppressed diminishes, thus tending to prevent an "overshoot" and subsequent low blood sugar (hypoglycemia), which is seen with some other oral hypoglycemic agents.