Dark patches in the skin
During type 2 diabetes and even before the disease starts, there’s a skin condition called acanthosis nigricans. You can see it as dark patches in the skin, mainly located in folds such as the armpit, the neck, and other joint areas. These dark patches usually appear in people with a reduced sensibility to insulin, and it might be used to detect type 2 diabetes and pre-diabetes (clinically named metabolic syndrome).
Thus, if you see dark patches in your skin and darker skin in your articulations, it would be a good idea to ask your doctor. Such a small symptom may turn out to be the leading sign for a doctor to diagnose metabolic syndrome and prevent type 2 diabetes. It may also help you detect the onset of diabetes and start treating your condition right away.