What are diabetic neuropathies?
Diabetic neuropathies are a family of nerve disorders caused by diabetes. People with diabetes can, over time, develop nerve damage throughout the body. Some people with nerve damage have no symptoms. Others may have symptoms such as pain, tingling, or numbness—loss of feeling—in the hands, arms, feet, and legs. Nerve problems can occur in every organ system, including the digestive tract, heart, and sex organs.

About 60 to 70 percent of people with diabetes have some form of neuropathy. People with diabetes can develop nerve problems at any time, but risk rises with age and longer duration of diabetes. The highest rates of neuropathy are among people who have had diabetes for at least 25 years. Diabetic neuropathies also appear to be more common in people who have problems controlling their blood glucose, also called blood sugar, as well as those with high levels of blood fat and blood pressure and those who are overweight.

What causes diabetic neuropathies?
The causes are probably different for different types of diabetic neuropathy. Researchers are studying how prolonged exposure to high blood glucose causes nerve damage. Nerve damage is likely due to a combination of factors:

metabolic factors, such as high blood glucose, long duration of diabetes, abnormal blood fat levels, and possibly low levels of insulin
neurovascular factors, leading to damage to the blood vessels that carry oxygen and nutrients to nerves
autoimmune factors that cause inflammation in nerves
mechanical injury to nerves, such as carpal tunnel syndrome
inherited traits that increase susceptibility to nerve disease
lifestyle factors, such as smoking or alcohol use
What are the symptoms of diabetic neuropathies?
Symptoms depend on the type of neuropathy and which nerves are affected. Some people with nerve damage have no symptoms at all. For others, the first symptom is often numbness, tingling, or pain in the feet. Symptoms are often minor at first, and because most nerve damage occurs over several years, mild cases may go unnoticed for a long time. Symptoms can involve the sensory, motor, and autonomic—or involuntary—nervous systems. In some people, mainly those with focal neuropathy, the onset of pain may be sudden and severe.

Symptoms of nerve damage may include

numbness, tingling, or pain in the toes, feet, legs, hands, arms, and fingers
wasting of the muscles of the feet or hands
indigestion, nausea, or vomiting
diarrhea or constipation
dizziness or faintness due to a drop in blood pressure after standing or sitting up
problems with urination
erectile dysfunction in men or vaginal dryness in women
weakness
Symptoms that are not due to neuropathy, but often accompany it, include weight loss and depression.

What are the types of diabetic neuropathy?
Diabetic neuropathy can be classified as peripheral, autonomic, proximal, or focal. Each affects different parts of the body in various ways.

Peripheral neuropathy, the most common type of diabetic neuropathy, causes pain or loss of feeling in the toes, feet, legs, hands, and arms.
Autonomic neuropathy causes changes in digestion, bowel and bladder function, sexual response, and perspiration. It can also affect the nerves that serve the heart and control blood pressure, as well as nerves in the lungs and eyes. Autonomic neuropathy can also cause hypoglycemia unawareness, a condition in which people no longer experience the warning symptoms of low blood glucose levels.
Proximal neuropathy causes pain in the thighs, hips, or buttocks and leads to weakness in the legs.
Focal neuropathy results in the sudden weakness of one nerve or a group of nerves, causing muscle weakness or pain. Any nerve in the body can be affected. Neuropathy Affects Nerves Throughout the Body
Peripheral neuropathy affects

toes
feet
legs
hands
arms
Autonomic neuropathy affects

heart and blood vessels
digestive system
urinary tract
sex organs
sweat glands
eyes
lungs
Proximal neuropathy affects

thighs
hips
buttocks
legs
Focal neuropathy affects

eyes
facial muscles
ears
pelvis and lower back
chest
abdomen
thighs
legs
feet

What is peripheral neuropathy?
Peripheral neuropathy, also called distal symmetric neuropathy or sensorimotor neuropathy, is nerve damage in the arms and legs. Your feet and legs are likely to be affected before your hands and arms. Many people with diabetes have signs of neuropathy that a doctor could note but feel no symptoms themselves. Symptoms of peripheral neuropathy may include

numbness or insensitivity to pain or temperature
a tingling, burning, or prickling sensation
sharp pains or cramps
extreme sensitivity to touch, even light touch
loss of balance and coordination
These symptoms are often worse at night.
Peripheral neuropathy affects the nerves in your toes, feet, legs, hands, and arms.

Peripheral neuropathy may also cause muscle weakness and loss of reflexes, especially at the ankle, leading to changes in the way a person walks. Foot deformities, such as hammertoes and the collapse of the midfoot, may occur. Blisters and sores may appear on numb areas of the foot because pressure or injury goes unnoticed. If foot injuries are not treated promptly, the infection may spread to the bone, and the foot may then have to be amputated. Some experts estimate that half of all such amputations are preventable if minor problems are caught and treated in time.

What is autonomic neuropathy?
Autonomic neuropathy affects the nerves that control the heart, regulate blood pressure, and control blood glucose levels. Autonomic neuropathy also affects other internal organs, causing problems with digestion, respiratory function, urination, sexual response, and vision. In addition, the system that restores blood glucose levels to normal after a hypoglycemic episode may be affected, resulting in loss of the warning symptoms of hypoglycemia.
Autonomic neuropathy affects the nerves in your heart, stomach, intestines, bladder, sex organs, sweat glands, eyes, and lungs.