Diabetes Mellitus (DM) is a heterogeneous group of disorders, characterised by hyperglycaemia and it's complications.
Hyperglycaemia according to American Diabetes Association is when
1. Fasting Blood Sugar level is more than or equal to 126mg/dL
2. Post prandial Blood sugar is more than or equal to 200mg/dL
The interesting part is here
DM Type 2 is either because of
i) increased glucose production by the liver ( when a person is sleeping) or
ii) impaired insulin secretion ( usually noticed after meals as insulin reserves are not sufficient or there is insulin resistance)
Let's talk of 2 scenarios,
In case i) Fasting blood glucose is high and
In case ii) Post Prandial blood glucose is high.
For case i), Metformin which is said to decrease the glucose production from liver is a better treatment option.
(Remember, Metformin also works against Insulin Resistance, so it also works in case ii !)
For case ii), since the problem is with insulin secretion or its resistance, Insulin Secretagogs work the best! Sulfonylurea increase the insulin secretion from ß cells in the pancreas, thereby tackling the problem.
Remember, Sulfonylureas are commonly used after Metformin!
If you want a super drug :P to tackle both these scenarios then Metformin and Thiazolidinediones are your best options. However, the side effect profile of the latter one is worrisome so used less often.
Here's one of my favourite quotes, Hardwork beats talent when talent doesn't work hard !