If you have diabetes, your blood glucose, or blood sugar, levels are too high. Over time, this can cause problems with other body functions, such as your kidneys, nerves, feet, and eyes. Having diabetes can also put you at a higher risk for heart disease and bone and joint disorders. Other long-term complications of diabetes include skin problems, digestive problems, sexual dysfunction, and problems with your teeth and gums.
Very high or very low blood sugar levels can also lead to emergencies in people with diabetes. The cause can be an underlying infection, certain medicines, or even the medicines you take to control your diabetes. If you feel nauseated, sluggish or shaky, seek emergency care.
NIH: National Institute of Diabetes and Digestive and Kidney Diseases