RELATED: If You Notice This in the Bathroom, It Could Be the First Sign of Diabetes. If you notice a velvety, dark patch—or multiple patches—on your skin, it could be an early sign of diabetes or pre-diabetes. The spots, referred to as acanthosis nigricans, usually begin “as an asymptomatic darkening and thickening of the skin, but can also progress to itching and larger patches,” says Navinder Jassil, MD, the director of diabetes and endocrinology at Deborah Specialty Physicians. These dark spots most commonly appear in skin folds, such as the neck, groin, or armpits, but they can also be found on palms, the soles of the feet, behind the knees, and on the elbows, according to nurse and educator Jenna Liphart Rhoads, PhD. RELATED: If You See This on Your Nails, It Could Be a Tell-Tale Sign of Diabetes. If you have acanthosis nigricans related to diabetes, it’s likely because you have too much insulin in your bloodstream, Rhoads explains. Per Healthline, “When you eat, your body converts carbohydrates into sugar molecules such as glucose. Some of this glucose is used for energy in your cells while the rest is stored. The hormone insulin must allow glucose to enter cells so that the cells can use glucose for energy.” Some people with diabetes develop an insulin resistance, so although insulin is being produced, the body is unable to use it correctly. According to Healthline, “This creates a buildup of glucose in the bloodstream, which can result in high levels of both blood glucose and insulin in your bloodstream.” Excess insulin can cause skin cells to reproduce at a more rapid rate. In some people, the new cells have more melanin, which then produces a darker patch of skin.ae0fcc31ae342fd3a1346ebb1f342fcb Although acanthosis nigricans is most commonly found in diabetes patients, it can be linked to other conditions. Jassil says the dark spots could be induced by genetic disorders, medication, malignancy, or autoimmune diseases. Endocrinologist and obesity medicine physician Aleem Kanji, MD, adds that polycystic ovary syndrome, Cushing syndrome, some cancers, and acromegaly can also cause acanthosis nigricans. RELATED: For more health content delivered straight to your inbox, sign up for our daily newsletter. There are a handful of other early signs of diabetes that you should know about. According to Healthline, frequent urination, extreme thirst, increased hunger, numbness, blurred vision, itchy skin, dry mouth, fatigue, and irritability can all be early signs of diabetes. If you experience any of these symptoms, make an appointment to talk to your doctor. RELATED: If You See This on Your Feet, You May Have Diabetes, Doctors Say.