There are four main types of diabetic neuropathy. You can have one or more than one type of neuropathy. Your symptoms will depend on the type you have and which nerves are affected. Usually, symptoms develop gradually. You may not notice anything wrong until considerable nerve damage has occurred.

Peripheral neuropathy

Peripheral neuropathy is the most common type of diabetic neuropathy. It affects the feet and legs first, followed by the hands and arms. Signs and symptoms of peripheral neuropathy are often worse at night, and may include:

• Numbness or reduced ability to feel pain or temperature changes
• Tingling or burning sensation
• Sharp pains or cramps
• Increased sensitivity to touch — for some people, even the weight of a bedsheet can be painful
• Muscle weakness
• Loss of reflexes, especially in the ankle
• Loss of balance and coordination
• Serious foot problems, such as ulcers, infections, and bone and joint pain

Autonomic neuropathy

The autonomic nervous system controls your heart, bladder, stomach, intestines, sex organs and eyes. Diabetes can affect nerves in any of these areas, possibly causing:

• A lack of awareness that blood sugar levels are low (hypoglycemia unawareness)
• Bladder problems, including urinary tract infections or urinary retention or incontinence
• Constipation, uncontrolled diarrhea or both
• Slow stomach emptying (gastroparesis), causing nausea, vomiting, bloating and loss of appetite
• Difficulty swallowing
• Increased or decreased sweating
• Problems controlling body temperature
• Changes in the way your eyes adjust from light to dark
• Increased heart rate at rest
• Sharp drops in blood pressure after sitting or standing that may cause you to faint or feel lightheaded
• Erectile dysfunction
• Vaginal dryness
• Decreased sexual response

Radiculoplexus neuropathy (diabetic amyotrophy)

Radiculoplexus neuropathy affects nerves in the thighs, hips, buttocks or legs. It's more common in people with type 2 diabetes and older adults. Other names for this type are diabetic amyotrophy, femoral neuropathy or proximal neuropathy.

Symptoms are usually on one side of the body, but sometimes may spread to the other side. You may have:

• Severe pain in a hip and thigh or buttock that occurs in a day or more
• Eventual weak and shrinking thigh muscles
• Difficulty rising from a sitting position
• Abdominal swelling, if the abdomen is affected
• Weight loss

Most people improve at least partially over time, though symptoms may worsen before they get better.

Mononeuropathy

Mononeuropathy, or focal neuropathy, is damage to a specific nerve in the face, middle of the body (torso) or leg. It's most common in older adults. Mononeuropathy often strikes suddenly and can cause severe pain. However, it usually doesn't cause any long-term problems.

Symptoms usually go away without treatment over a few weeks or months. Your specific signs and symptoms depend on which nerve is involved. You may have pain in the:

• Shin or foot
• Lower back or pelvis
• Front of thigh
• Chest or abdomen

Mononeuropathy may also cause nerve problems in the eyes and face, leading to:

• Difficulty focusing
• Double vision
• Aching behind one eye
• Paralysis on one side of your face (Bell's palsy)

Sometimes mononeuropathy occurs when something is pressing on a nerve (nerve compression). Carpal tunnel syndrome is a common type of compression neuropathy in people with diabetes. It can cause numbness or tingling in your hand or fingers, except your pinkie (little finger). Your hand may feel weak, and you may drop things.

Damage to nerves and blood vessels

The exact cause likely differs for each type of neuropathy. Researchers think that over time, uncontrolled high blood sugar damages nerves and interferes with their ability to send signals, leading to diabetic neuropathy. High blood sugar also weakens the walls of the small blood vessels (capillaries) that supply the nerves with oxygen and nutrients.

However, a combination of factors may lead to nerve damage, including:

• Inflammation in the nerves caused by an autoimmune response. The immune system mistakes nerves as foreign and attacks them.
• Genetic factors unrelated to diabetes may make some people more likely to develop nerve damage.
• Smoking and alcohol abuse damage both nerves and blood vessels and significantly increase the risk of infection.

Anyone who has diabetes can develop neuropathy, but these risk factors make you more likely to get nerve damage:

• Poor blood sugar control. Uncontrolled blood sugar puts you at risk of every diabetes complication, including nerve damage.
• Diabetes history. Your risk of diabetic neuropathy increases the longer you have diabetes, especially if your blood sugar isn't well-controlled.
• Kidney disease. Diabetes can damage the kidneys. Kidney damage sends toxins into the blood, which can lead to nerve damage.
• Being overweight. Having a body mass index (BMI) greater than 24 may increase your risk of diabetic neuropathy.
• Smoking. Smoking narrows and hardens your arteries, reducing blood flow to your legs and feet. This makes it more difficult for wounds to heal and damages the peripheral nerves.

Diabetic neuropathy can cause a number of serious complications, including:

• Loss of a toe, foot or leg. Nerve damage can make you lose feeling in your feet. Foot sores and cuts may silently become severely infected or turn into ulcers. Even minor foot sores that don't heal can turn into ulcers. In severe cases, infection can spread to the bone, and ulcers can lead to tissue death (gangrene). Removal (amputation) of a toe, foot or even the lower leg may be necessary.
• Joint damage. Nerve damage can cause a joint to deteriorate, causing a condition called Charcot joint. This usually occurs in the small joints in the feet. Symptoms include loss of sensation and joint swelling, instability and sometimes joint deformity. Prompt treatment can help you heal and prevent further joint damage.
• Urinary tract infections and urinary incontinence. If the nerves that control your bladder are damaged, you may be unable to fully empty your bladder. Bacteria can build up in the bladder and kidneys, causing urinary tract infections. Nerve damage can also affect your ability to feel when you need to urinate or to control the muscles that release urine, leading to leakage (incontinence).
• Hypoglycemia unawareness. Low blood sugar (below 70 milligrams per deciliter, or mg/dL) normally causes shakiness, sweating and a fast heartbeat. But if you have autonomic neuropathy, you may not notice these warning signs.
• Sharp drops in blood pressure. Damage to the nerves that control blood flow can affect your body's ability to adjust blood pressure. This can cause a sharp drop in pressure when you stand after sitting (orthostatic hypotension), which may lead to dizziness and fainting.
• Digestive problems. If nerve damage strikes your digestive tract, you can have constipation or diarrhea, or bouts of both. Diabetes-related nerve damage can lead to gastroparesis, a condition in which the stomach empties too slowly or not at all. This can interfere with digestion and severely affect blood sugar levels and nutrition. Signs and symptoms include nausea, vomiting and bloating.
• Sexual dysfunction. Autonomic neuropathy often damages the nerves that affect the sex organs. Men may experience erectile dysfunction. Women may have difficulty with lubrication and arousal.
• Increased or decreased sweating. Nerve damage can disrupt how your sweat glands work and make it difficult for your body to control its temperature properly. Some people with autonomic neuropathy have excessive sweating, particularly at night or while eating. Too little or no sweating at all (anhidrosis) can be life-threatening.