Nerve damage, blindness, and kidney disease are common complications of type 1 diabetes.

People with type 1 diabetes lack the hormone insulin, which regulates the body's use of glucose for energy.

This results in high blood glucose, or hyperglycemia, as glucose builds up in the bloodstream.

The main treatment for type 1 diabetes is lifelong insulin therapy, which lowers blood glucose and allows the body to use glucose as fuel.

High blood glucose is associated with a number of symptoms, such as increased urination, extreme thirst or hunger, and slow-healing sores.

Over time, elevated blood glucose levels can also lead to various complications in different areas of the body, since hyperglycemia damages many different types of tissue.

Diabetic Neuropathy

Neuropathy is a type of nerve damage, or nerve dysfunction.

In people with diabetes, neuropathy may develop when high blood glucose levels damage blood vessels that supply oxygen to nerves.

As many as 60 to 70 percent of all people with diabetes have some form of neuropathy, according the National Institute of Diabetes and Digestive and Kidney Diseases.

A common form of diabetic neuropathy is peripheral neuropathy, which causes numbness, pain, and weakness in the toes, feet, legs, hands, or arms.

Because of this widespread complication, people with diabetes must take special care of their feet.

Nerve damage may cause people to lose feeling in their feet, leading to unnoticed injuries that may become infected (poor blood flow can also lead to slower healing).

What's more, nerve damage may cause foot deformations that lead to additional pressure at certain points on the feet — and these pressure points may develop into blisters, sores, or ulcers.

Diabetic neuropathy may also affect various other areas of the body, including the digestive tract, heart, sex organs, facial muscles, buttocks, and urinary tract.

Diabetic Retinopathy

By affecting the blood vessels in the retina, diabetes may cause retinopathy, a type of eye disease.

In some people, diabetic retinopathy causes blood vessels in the eye to swell and leak fluid, while in others, there is abnormal growth of new blood vessels on the retina.

Diabetic retinopathy often leads to blurred vision, and sometimes blindness.

In fact, it’s the leading cause of blindness among adults 20 to 74 years old, according to a 2010 report in the journal Endocrinology and Metabolism Clinics of North America.

People with diabetes are also more likely to develop cataracts (cloudiness of the eye lens) and glaucoma (optic nerve damage).

Diabetic Nephropathy

About 20 to 40 percent of people with diabetes develop nephropathy, a form of kidney disease, according to the 2010 report.

The kidneys work to filter blood, keeping it clean of waste products.

Diabetic nephropathy develops when high blood glucose levels damage blood vessels in the kidneys, causing them to gradually lose their filtering ability — and allowing waste products to build up in the body.

The first symptom of nephropathy is often swelling in certain areas of the body. In many cases, however, nephropathy doesn't cause any symptoms until almost all kidney function is gone.

Dialysis is often necessary if kidney function drops below a certain level. If the kidneys fail completely, a kidney transplant may be necessary.

Other Diabetes Complications

Type 1 diabetes can also lead to other complications, including:

High blood pressure

Cardiovascular disease

Stroke

Skin and mouth infections

Gastroparesis (delayed gastric emptying), a type of neuropathy

Sexual dysfunction

Depression

Diabetes can also cause pregnancy complications — such as an increased risk of stillbirth, miscarriages, and birth defects — if blood glucose is not controlled properly.