Diabetes Complications

High blood sugar (glucose) that circulates in the bloodstream instead of being absorbed into cells damages nerves and blood vessels throughout the body and, ultimately, the major organs such as the kidneys and heart. It has been said that there isn’t a system in the body that isn’t affected by diabetes.

The good news is that diabetes can be managed and the risk of developing complications significantly reduced. A nationwide study conducted from 1983-1993 called the Diabetes Control and Complications Trial showed that when blood sugar levels are checked consistently throughout the day – and kept close to normal – complications of the disease can be reduced by as much as 70 percent. This method is also referred to as "tight control" of blood sugar and has become standard of care in diabetes management.

Diabetic Neuropathy (Nerve Damage)

Approximately 60-70 percent of people with diabetes have mild to severe forms of nerve damage. Often the first symptoms of diabetes are tingling, numbness or pain in some part of the body, which is an indication that nerves have been damaged. Neuropathy from diabetes can affect many different parts of the body, including the lower limbs (legs, feet), the bladder and the gastrointestinal tract.

Several theories exist as to why diabetes has such a devastating effect on the nervous system. One theory holds that excess sugar in the bloodstream reacts negatively with an enzyme in the cells surrounding the nerves and damages them. Another theory suggests that decreased blood flow to nerves, from damaged blood vessels caused by diabetes, results in neuropathy.

In general, there are three types of neuropathy: sensory, autonomic and motor. Sensory neuropathy is the most common, affecting how we perceive temperature, texture and pain. Autonomic neuropathy affects nerves involved in involuntary actions in the body such as emptying of the stomach, intestines and bladder. Motor neuropathy, affecting the nerves involved in movement, is rare in diabetes.

Several of the more common conditions associated with diabetic neuropathy include the following:

  • Distal neuropathy affects the hands and feet and is the most common form of diabetic neuropathy. It usually affects both hands or both feet, but may affect only one hand or foot.

  • Diabetic amyotrophy affects the nerves in the thighs and may be present in one or both legs.

  • Gastroparesis affects the nerves in the stomach, preventing it from emptying as it should. Food that is not absorbed normally can cause malnutrition and hypoglycemia (low blood sugar) and, later, hyperglycemia (high blood sugar) as the meal is finally digested. The condition can also cause vomiting, bloating and pain in the stomach.

  • Diabetic diarrhea can occur when the nerves in the small intestine are affected. If the nerves in the large intestine are damaged, constipation may result. Additionally, if nerves affecting the sphincter muscles in the rectum are involved, stools may be passed without warning.

  • Neuropathy of the bladder can occur when the nerves that bring sensation from and control the bladder no longer function properly, allowing urine to stay in the bladder. The condition can lead to urinary tract infections.

  • Charcot joint may occur if the bones in the feet develop fractures and the foot becomes misaligned. The condition can be painless because nerves were damaged from diabetes before the fracture developed. The foot or feet may then lose muscle support, eventually becoming deformed.

  • Foot drop, an inability to pick up the foot, may occur if nerve and muscle damage is present.

  • Postural hypotension (low blood pressure when standing) can occur when nerves are damaged and cannot compensate for the rise in blood pressure. Fainting or dizziness can result.

Diabetic Retinopathy (Eye Disease)

Approximately 12,000-24,000 people with diabetes lose their eyesight each year because of damage to the small blood vessels in the retina. The retina is the light-sensitive tissue at the back of the eye. People with diabetes are also at higher risk of developing cataracts (loss of transparency in the lenses of the eyes) and glaucoma (excessive pressure of fluid in the eye).

In diabetic retinopathy, the blood vessels in the retina weaken and may leak fluid onto the macula, the area in the eye that allows precise vision. The macula then swells, blurring vision. If the disease progresses, new fragile blood vessels can grow along the retina (called proliferative retinopathy) that also leak blood, eventually causing serious hemorrhage, scarring and retinal damage leading to poor vision and even blindness.

Yearly eye exams are recommended for people with diabetes. Treatment with laser surgery or vitrectomy has a high success rate (90 percent) but only if permanent damage has not occurred to the retina.

Diabetic Nephropathy (Kidney Disease)

An estimated 28,000 people with diabetes develop kidney failure each year because of damage, over time, to the kidney’s sensitive filtering system, which removes waste products from blood. Eventually, the kidneys lose their ability to perform this vital function and patients must rely on dialysis or a kidney transplantation.

Uncontrolled high blood pressure (hypertension) also can damage the kidneys, presenting a double whammy for patients with diabetes. Additionally, people with diabetes who did not have high blood pressure before can develop it in later stages of kidney disease. This situation occurs when physical changes in the kidneys cause a rise in blood pressure.

People with diabetes should have blood and urine tests annually to check for early signs of kidney disease.

Cardiovascular Complications (Heart and Blood Vessel Disease)

Heart and blood vessel disease are the most common long-term complications of uncontrolled diabetes. High glucose levels in the blood damage blood vessels by making the walls of the vessels thicker. As a result, blood has a harder time passing through them.

Additionally, diabetes causes higher lipid (fat) levels in blood that can lead to clogged and narrowed arteries. High blood pressure is another risk factor for clogged arteries. The condition, called atherosclerosis, can occur anywhere in the body and may eventually lead to angina (pain in the heart), heart attack, stroke, and pain in the legs or feet. People with diabetes are two to four times more likely to have a stroke or heart attack than those without the disease.

Stopping smoking, losing weight and keeping blood sugars, cholesterol and blood pressure under control are some of the ways to reduce risks of developing heart and blood vessel disease. The American Diabetes Association recommends a blood glucose goal of 80-120 mg/dl before meals, a cholesterol level of less than 200 mg/dl and a blood pressure reading of less than 130/85.

Diabetic ketoacidosis

Ketoacidosis occurs from a lack of insulin, primarily in individuals with type 1 diabetes. Without insulin, the body breaks down fat instead of metabolizing sugar properly for energy. The process produces ketones, which are dangerous byproducts of fat similar in chemical composition to acetone, which is found in solvents. The ketones turn the blood more acidic, which can be a life-threatening condition. Because ketones are released in urine, a simple urine test can detect their presence. People with type 1 diabetes should test for ketones when blood glucose is elevated and during times of illness. The main symptoms of ketoacidosis are nausea and vomiting, profound weakness and hyperventilation.

Diabetic ketoacidosis must often be treated in the hospital with insulin and intravenous fluids. The person must get treatment immediately to avoid lapsing into a coma.

Hyperosmolar coma

This condition occurs primarily in people with type 2 diabetes. It is caused from a reduced level of insulin and increased insulin resistance that cause blood sugar to rise dangerously high. Unlike the condition ketoacidosis, high acid levels in the blood are usually not present. However, dehydration may be present and may be serious.

Hyperosmolar coma

is treated in the hospital with a small amount of insulin and intravenous fluids. The person must get treatment immediately to avoid lapsing into a coma.

Hypoglycemia (low blood sugar)

Hypoglycemia can be caused by a delayed or skipped meal, increased activity or taking more diabetes medicine than is needed. The condition can affect people with type 1 or type 2 diabetes who use insulin or sulfonylureas.

Hypoglycemia is treated by immediately ingesting 15 grams of carbohydrate. This equals ½ cup of juice, three glucose tablets, ½ cup of a regular soft drink or other carbohydrate food. The treatment should be followed by a meal if it is mealtime or a snack.


Men with diabetes run a greater risk of developing impotence because of blood vessel and nerve damage caused from high glucose (sugar) levels in the blood. There are many effective treatments for impotence including medication (Viagra®), devices and surgery.

Stopping smoking, which constricts blood vessels, and keeping blood fats, sugars and cholesterol under control are some of the ways to reduce risks of developing impotence.

Foot problems

Nerve and blood vessel damage – causing a lack of pain sensation and decreased blood flow – can result in serious foot problems. People with diabetes are particularly at risk for foot ulcers and infections: they may not know, for example, that an injury has occurred to the foot. And a lack of blood flow may slow the healing process. In severe cases, sores may never heal, leading to gangrene and amputation.

For people with diabetes, it is important always to wear shoes and to inspect your feet every day, including the bottoms of your feet, for sores and infections.

American Diabetes Association
Centers for Disease Control and Prevention (CDC)