There are four main types of diabetic neuropathy. You may have just one type or symptoms of several types. Most develop gradually, and you may not notice problems until considerable damage has occurred.
The signs and symptoms of diabetic neuropathy vary, depending on the type of neuropathy and which nerves are affected.
Peripheral neuropathy is the most common form of diabetic neuropathy. Your feet and legs are often affected first, followed by your hands and arms. Possible signs and symptoms of peripheral neuropathy include:
- Numbness or reduced ability to feel pain or changes in temperature, especially in your feet and toes
- A tingling or burning feeling
- Sharp, jabbing pain that may be worse at night
- Pain when walking
- Extreme sensitivity to the lightest touch — for some people, even the weight of a sheet can be agonizing
- Muscle weakness and difficulty walking
- Serious foot problems, such as ulcers, infections, deformities, and bone and joint pain
The autonomic nervous system controls your heart, bladder, lungs, stomach, intestines, sex organs and eyes. Diabetes can affect the nerves in any of these areas, possibly causing:
- A lack of awareness that blood sugar levels are low (hypoglycemia unawareness)
- Bladder problems, including frequent urinary tract infections or urinary incontinence
- Constipation, uncontrolled diarrhea or a combination of the two
- Slow stomach emptying (gastroparesis), leading to nausea, vomiting and loss of appetite
- Difficulty swallowing
- Erectile dysfunction in men
- Vaginal dryness and other sexual difficulties in women
- Increased or decreased sweating
- Inability of your body to adjust blood pressure and heart rate, leading to sharp drops in blood pressure when you rise from sitting or lying down (orthostatic hypotension) that may cause you to feel lightheaded or even faint
- Problems regulating your body temperature
- Changes in the way your eyes adjust from light to dark
- Increased heart rate when you're at rest
Radiculoplexus neuropathy (diabetic amyotrophy)
Instead of affecting the ends of nerves, like peripheral neuropathy, radiculoplexus neuropathy affects nerves in the thighs, hips, buttocks or legs. Also called diabetic amyotrophy, femoral neuropathy, or proximal neuropathy, this condition is more common in people with type 2 diabetes and older adults. Symptoms are usually on one side of the body, though in some cases symptoms may spread to the other side too. Most people improve at least partially over time, though symptoms may worsen before they get better. This condition is often marked by:
- Sudden, severe pain in your hip and thigh or buttock
- Eventual weak and atrophied thigh muscles
- Difficulty rising from a sitting position
- Abdominal swelling, if the abdomen is affected
- Weight loss
Mononeuropathy involves damage to a specific nerve. The nerve may be in the face, torso or leg. Mononeuropathy, which may also be called focal neuropathy, often comes on suddenly. It's most common in older adults. Although mononeuropathy can cause severe pain, it usually doesn't cause any long-term problems. Symptoms usually diminish and disappear on their own over a few weeks or months. Signs and symptoms depend on which nerve is involved and may include:
- Difficulty focusing your eyes, double vision or aching behind one eye
- Paralysis on one side of your face (Bell's palsy)
- Pain in your shin or foot
- Pain in the front of your thigh
- Chest or abdominal pain
Sometimes mononeuropathy occurs when a nerve is compressed. Carpal tunnel syndrome is a common type of compression neuropathy in people with diabetes.
Signs and symptoms of carpal tunnel syndrome include:
- Numbness or tingling in your fingers or hand, especially in your thumb, index finger, middle finger and ring finger
- A sense of weakness in your hand and a tendency to drop things
When to see a doctor
Seek medical care if you notice:
- A cut or sore on your foot that doesn't seem to be healing, is infected or is getting worse
- Burning, tingling, weakness or pain in your hands or feet that interferes with your daily routine or your sleep
- Changes in your digestion, urination or sexual function
These symptoms don't always indicate nerve damage, but they may signal other problems that require medical care. In either case, early diagnosis and treatment offer the best chance for controlling symptoms and preventing more-severe problems.
Even minor sores on the feet that don't heal can turn into ulcers. In the most severe cases, untreated foot ulcers may become gangrenous — a condition in which the tissue dies — and require surgery or even amputation of your foot. Early treatment can help prevent this from happening.
Damage to nerves and blood vessels
Prolonged exposure to high blood sugar (glucose) can damage delicate nerve fibers, causing diabetic neuropathy. Why this happens isn't completely clear, but a combination of factors likely plays a role, including the complex interaction between nerves and blood vessels. High blood glucose interferes with the ability of the nerves to transmit signals. It also weakens the walls of the small blood vessels (capillaries) that supply the nerves with oxygen and nutrients.
Other factors that may contribute to diabetic neuropathy include:
- Inflammation in the nerves caused by an autoimmune response. This occurs when your immune system mistakenly attacks part of your body as if it were a foreign organism.
- Genetic factors unrelated to diabetes that make some people more susceptible to nerve damage.
- Smoking and alcohol abuse, which damage both nerves and blood vessels and significantly increase the risk of infections.
Anyone who has diabetes can develop neuropathy, but these factors make you more susceptible to nerve damage:
- Poor blood sugar control. This is the greatest risk factor for every complication of diabetes, including nerve damage. Keeping blood sugar consistently within your target range is the best way to protect the healthof your nerves and blood vessels.
- Length of time you have diabetes. Your risk of diabetic neuropathy increases the longer you have diabetes, especially if your blood sugar isn't well controlled. Peripheral neuropathy is most common in people who have had diabetes for at least 25 years.
- Kidney disease. Diabetes can cause damage to the kidneys, which may increase the toxins in the blood and contribute to nerve damage.
- 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 integrity of the peripheral nerves.
Diabetic neuropathy can cause a number of serious complications, including:
Loss of a limb. Because nerve damage can cause a lack of feeling in your feet, cuts and sores may go unnoticed and eventually become severely infected or ulcerated — a condition in which the skin and soft tissues break down. The risk of infection is high because diabetes reduces blood flow to your feet.
Infections that spread to the bone and cause tissue death (gangrene) may be impossible to treat and require amputation of a toe, foot or even the lower leg. More than half the nontraumatic lower limb amputations performed every year in the United States are due to diabetes.
- Charcot joint. This occurs when a joint, usually in the foot, deteriorates because of nerve damage. Charcot joint is marked by loss of sensation, as well as swelling, instability and sometimes deformity in the joint itself.
- Urinary tract infections and urinary incontinence. Damage to the nerves that control your bladder can prevent it from emptying completely. This allows bacteria to multiply in your bladder and kidneys, leading to 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.
- Hypoglycemia unawareness. Normally, when your blood sugar drops too low — below 70 milligrams per deciliter (mg/dL), or below 3.9 millimoles per liter (mmol/L) — you develop symptoms such as shakiness, sweating and a fast heartbeat. These symptoms alert you to the problem so that you can take steps to raise your blood sugar quickly. Autonomic neuropathy can interfere with your ability to notice these symptoms. This is extremely serious — untreated hypoglycemia can be fatal.
- Low blood pressure. Damage to the nerves that control circulation 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. Damage to the nerves in the digestive system can cause a range of problems, including severe constipation or diarrhea — or alternating bouts of constipation and diarrhea — as well as nausea, vomiting, bloating and loss of appetite. One particularly serious digestive problem is gastroparesis, a condition in which the stomach empties too slowly or not at all. This can interfere with digestion, cause nausea and vomiting, and severely affect blood sugar levels and nutrition.
- Sexual dysfunction. Autonomic neuropathy often damages the nerves that affect the sex organs, leading to erectile dysfunction in men and problems with lubrication and arousal in women.
- Increased or decreased sweating. When the sweat glands don't function normally, your body isn't able to regulate its temperature properly. A reduced or complete lack of perspiration (anhidrosis) can be life-threatening. Autonomic neuropathy also causes excessive sweating, particularly at night.
- Social isolation. The pain, disability and embarrassment caused by nerve damage can rob people — particularly older adults — of their independence, leaving them increasingly isolated and depressed.
You can help prevent or delay diabetic neuropathy and its complications by keeping your blood sugar consistently well controlled, taking good care of your feet and following a healthy lifestyle.
Blood sugar control
Keeping your blood sugar tightly controlled every day is a big commitment. It requires constant monitoring and, if you take insulin, frequent doses of medication. But keeping your blood sugar as close to normal as possible is the best way to help prevent neuropathy and other complications of diabetes. Consistency is important because shifts in blood sugar levels can accelerate nerve damage.
For the best control, aim for a blood glucose level from 70 to 130 mg/dL (3.9 to 7.2 mmol/L) before meals and an A1C reading that is less than 7 percent. An A1C test measures your average blood sugar level over a period of two to three months. The American Diabetes Association recommends that people with diabetes have an A1C test at least twice a year if blood sugar levels are consistently in a healthy range. If your blood sugar isn't well controlled or you change medications, get tested more often.
Foot problems, including sores that don't heal, ulcers and even amputation, are a common complication of diabetic neuropathy. But you can prevent many of these problems by having a comprehensive foot exam at least once a year, having your doctor check your feet at each office visit and taking good care of your feet at home.
To protect the health of your feet:
- Check your feet every day. If you can't see some parts of your feet, use a mirror or ask a family member or friend to examine those areas. Look for blisters, cuts, bruises, cracked and peeling skin, and redness and swelling.
- Keep your feet clean and dry. Wash your feet every day with lukewarm water. If your feet can't sense temperature, test the water by touching a dampened washcloth to a sensitive part of your body, such as your neck or wrist. Dry your feet gently by blotting or patting. Rubbing may damage your skin. Dry carefully between your toes. Then moisturize your skin thoroughly to prevent cracking. Try to avoid getting lotion between your toes, however, as this can encourage fungal growth.
- Trim your toenails carefully. Cut your toenails straight across, and file the edges carefully so there are no sharp edges. If you're not able to reach your feet, ask a family member, your doctor or a podiatrist to help you.
- Wear clean, dry socks. You don't need to buy special socks for people with diabetes, but do look for socks made of cotton or moisture-wicking fibers that don't have tight bands or thick seams.
- Wear cushioned shoes that fit well. Always wear shoes to protect your feet from injury. Make sure that your shoes fit properly. It's best to try on shoes later in the day when your feet are more swollen to ensure that the shoes aren't too tight. A podiatrist can teach you how to buy properly fitted shoes and to prevent problems such as corns and calluses.
If problems do occur, a podiatrist can help treat them to prevent more-serious conditions from developing. Even small sores can quickly turn into severe infections if left untreated.
Shoes that fit well can be costly. If you qualify for Medicare, your plan may cover the cost of at least one pair of shoes a year. For more information, talk to your doctor or diabetes educator.