High blood sugar, technically termed hyperglycemia, occurs when the body has deficient amounts of insulin or when the body can't utilize insulin properly. Hyperglycemia can happen to most anyone; however, it is the primary cause of complications in people with diabetes, according to the American Diabetes Association--ADA. While occasional, mild peaks in blood sugar are unlikely to cause serious health problems; severe cases can pose numerous negative effects, some of which are life-threatening.
Eye Problems
If high blood sugar isn't properly managed eye health and vision can suffer. According to the ADA, people with diabetes are 60 percent more likely to develop cataracts than non-diabetics due to chronic high blood sugar. High blood sugar can also lead to forms of retinopathy--disorders of the retina, or back of the eye, glaucoma--the result of built-up pressure in the eye--and poor eyesight. Failure to manage or seek treatment for hyperglycemia further increases these risks. People who develop eye problems associated with hyperglycemia may require medical treatment, eyeglasses or, in some cases, surgery.
Peripheral Neuropathy
Peripheral neuropathy refers to nerve damage that causes tingling, numbness or pain in a person's extremities. According to MayoClinic.com, neuropathy is a potential long-term complication of high blood sugar. Peripheral neuropathy usually develops first in the feet and hands. Numbness may then spread into a person's arms and legs. Though symptoms of nerve damage vary, they may include sharp, jabbing or burning pain in the extremities, reduced coordination, muscle weakness, paralysis and bladder problems, if nerves in the bladder are affected.
Foot Problems
When high blood sugar causes nerve damage in the feet, additional complications may arise. A person may not feel a blister or wound from stepping on a sharp object and fail to treat it, which can give way to foot damage and infection. Nerve damage associated with hyperglycemia can also alter the shape of a person's feet and toes, according to the ADA, making it difficult to walk properly without use of a brace or therapeutic shoes. Foot problems can also increase risk of falling and injuries, if mobility becomes affected.
Ketoacidosis
If high blood sugar remains untreated for an elongated period of time and insulin problems prevent use of glucose for energy, the body turns to fat for energy. In turn, the body produces toxic acids called ketones. When the body can't fully rid itself of excess ketones, the result is a life-threatening condition known as ketoacidosis or diabetic coma. Initial symptoms of ketoacidosis include frequent urination, fruit-smelling breath, difficulty breathing, nausea, vomiting, mental confusion and extreme dry mouth and thirst. The ADA suggests prompt emergency medical care at the first sign of ketoacidosis.
