Like type 1 diabetes, type 2 diabetes is a metabolic disorder in which blood glucose rises because it isn't being effectively balanced and metabolized into cell energy by insulin. The similarities in physiology between the two diseases end there, however.

Type 2 diabetes is not initially caused by the absence of the hormone insulin, as is the case with type 1, but rather by the body's inability to use insulin properly. People with type 2 have a condition called insulin resistance. They can produce insulin, usually in sufficient amounts at first, but when it's time for the insulin to bind to the insulin receptor — the gateway to cells in muscle, fat, and liver tissue — and initiate chemical signaling that allows the glucose in to be metabolized into cellular energy, something goes wrong and insulin resistance results.

In other words, it's like trying to fit a square peg (insulin) into a round hole (insulin receptor). As a result, glucose doesn't enter the cells and instead builds up in the bloodstream, resulting in high blood sugar levels.

The second condition that contributes to type 2 diabetes is insulin deficiency — the pancreas also has difficulty producing sufficient amounts of insulin to process the rising blood glucose levels. Eventually it does not have sufficient amounts to overcome the deficit.

Over time, inflammatory processes in the body and the toxic effects of long-term high glucose levels on the insulin-producing beta cells on the pancreas (glucotoxicity) can make insulin deficiency worse, and drug therapy is eventually required to preserve or recover beta cell function.