Sitagliptin (trade name Januvia) is the first in a new class of drugs for diabetes – the dipeptidyl peptidase-4 (DPP-4) inhibitors. This new, oral hypoglycaemic agent has recently been approved for the treatment of type 2 diabetes. It is available on prescription and can be prescribed in primary care. Principal advantages include lack of weight gain and hypoglycaemia, which should make sitagliptin very popular with patients. This article looks at what a DPP-4 inhibitor is and how it works to lower blood glucose, as well as where this class of drug fits into current practice.