system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 Why do diabetics sometimes have to have limbs, particularly their legs, amputated?
gpt
Diabetes is a disease in people where the body does not produce insulin (type 1 diabetes) or does not use glucose properly (type 2 diabetes). In both instances, there can be a high level of glucose, or sugar, in the blood. 

Uncontrolled high blood sugar damages nerves and interferes with their ability to send signals, leading to diabetic neuropathy (tingling and loss of feeling$. High blood sugar also weakens the walls of the small blood vessels (capillaries) that supply the nerves with oxygen and nutrients.

The combination of poor circulation and lack of feeling in the limbs leaves those areas prone to infection or cell death (from not receiving oxygen or nutrients). Infection can go unnoticed for quite some time, past the point of recovery and would require amputation so the infection does not spread. It is difficult/impossible to get an appropriate amount of antibiotic/antifungal medication to an area with poor circulation.