Diabetic Foot Problems: Numbness, Ulcers and Prevention

Diabetic neuropathy is nerve damage caused by diabetes. The nerves most at risk are the longest ones in the body, those running from the spine to the toes, which is why the feet are affected first.

Doctors call the common form peripheral neuropathy (or distal symmetric polyneuropathy). It starts in the toes of both feet and moves up the legs slowly, over years. By the time it reaches the knees, the fingertips may be involved too.

It does not behave the same way in everyone. One person has burning pain that keeps them awake. Another feels nothing at all and only learns about it when a doctor tests their feet. Some people have both, with feet that hurt and yet cannot feel a pin.

What are the types of diabetic neuropathy?

Peripheral neuropathy is behind most diabetic foot ulcers, and it is the main subject of this guide.

Glucose that stays high for years injures nerve fibres directly. It also damages the very small blood vessels that keep those nerves alive. Starved and injured, the nerves gradually stop reporting pain, heat and pressure.

At the same time, diabetes speeds up narrowing of the larger arteries in the legs, a condition called peripheral arterial disease (PAD). A foot with poor blood supply heals slowly. A scrape that should close in a week can stay open for months.

High sugar also blunts the body's response to infection, which is why a small crack in the heel can become a spreading infection in a short time. And when the nerves that control sweating are affected, the skin of the foot turns dry and splits, giving germs a way in.

Who is more likely to get diabetic neuropathy?

Duration and control matter most. The longer someone has had diabetes, and the longer their HbA1c (average sugar over about 3 months) has stayed high, the greater the risk. Smoking and chewing tobacco add to it, as do high blood pressure, high cholesterol and triglycerides, extra weight around the waist, kidney disease from diabetes and regular alcohol use.

Long-term metformin use can lower vitamin B12 in some people, and low B12 can cause or worsen numbness on its own.

Neuropathy is sometimes already present on the day type 2 diabetes is diagnosed. In many people, sugar has been high for years before the first test.

The first symptoms usually appear in the toes and soles of both feet, and patients describe them in their own ways. Burning, as if the soles are on hot sand. Pins and needles. A feeling of walking on cotton wool, or of wearing socks when the feet are bare. Sudden shooting or electric-shock pains. Skin so sensitive that the touch of a bedsheet is uncomfortable.

Other signs are easy to miss. Chappals slip off without the wearer noticing. Calf cramps come at night. Walking feels unsteady in the dark, or on a muddy path, because the feet are no longer telling the brain exactly where the ground is.

A large number of people have no symptoms whatsoever. That is the reason routine foot checks exist.

Why does burning in the feet get worse at night?

Lying still in a quiet room, with nothing else to occupy the mind, damaged nerves feel louder. Many people throw off the blanket or press their feet against the cool floor.

Some soak their feet in hot water for relief. On numb skin this is dangerous. The foot cannot tell how hot the water is, and deep burns can happen without any pain at the time.

Is numbness in the feet always caused by diabetes?

No. Low vitamin B12, an underactive thyroid, alcohol, kidney disease, some medicines and nerve compression in the lower spine can produce the same sensations, and several of these can be treated. Numbness confined to one foot, or weakness that develops over days or weeks, does not fit the usual pattern of diabetic neuropathy and needs further assessment.

A diabetic foot ulcer is an open wound, most often on the sole, the tip or side of a toe, or the heel, that is slow to heal. It rarely starts with anything dramatic.

The sequence is fairly predictable. Neuropathy has dulled sensation. A tight shoe rubs, or a small stone lodges in a chappal, and there is no pain to make the person stop. They carry on walking for hours, then days. Thick hard skin (callus) forms over the pressure point, and beneath it the tissue quietly breaks down. One day the skin gives way. Germs enter, and with high sugar and poor circulation, the body struggles to contain them. Without treatment, the infection can travel into deeper tissue and bone.

What causes foot injuries in everyday life?

In Bongaigaon and across Lower Assam, the causes are usually ordinary. Walking barefoot is the most common, whether around the house, in the courtyard, in the fields, or at the namghar, temple or mosque. Thin rubber chappals are comfortable but offer little against thorns and sharp gravel on a long walk.

Occasions bring their own risk. A pair of new shoes worn all day at a wedding or on a Bihu or Puja visit can raise a blister that the wearer never feels.

The monsoon is hard on diabetic feet. Hours in wet footwear soften the skin and let fungus settle between the toes, and the cracks it leaves are an easy route for bacteria. In winter, the danger flips to heat, with burns from sitting too close to a fire or heater, or from a hot water bottle left against the feet overnight.

Then there are corns and calluses shaved with a blade at home or by a roadside corn cutter, and toenails cut too short or dug out at the corners. Both are frequent starting points for infection.

What is peripheral arterial disease, and how does it affect the feet?

Peripheral arterial disease is narrowing of the arteries that supply the legs. In diabetes it is common and can go unnoticed for a long time.

The typical complaint is calf pain or tightness while walking that eases after a few minutes of standing still. Look also for a foot that feels cold, or colder than the other one, thin and shiny skin on the shins, little or no hair on the toes, and weak pulses at the ankle. Toe wounds that will not close, and foot pain at night that settles when the leg hangs over the side of the bed, point the same way.

When the leg arteries are narrowed, the arteries of the heart and brain often are too. A finding of PAD therefore prompts a wider look atheart health.

What is Charcot foot?

Charcot foot is an uncommon complication in which the bones and joints of a numb foot weaken, fracture and gradually collapse. It typically presents as a hot, red, swollen foot with much less pain than the swelling would suggest.

Because it looks like a sprain or an infection, the diagnosis is sometimes delayed. Treatment depends on keeping weight off the foot entirely in the early phase, and late treatment can leave the foot permanently misshapen. Anyone with neuropathy who notices one foot becoming warm and swollen should be seen promptly.

Diagnosis depends mainly on a careful examination of the feet. It is quick and does not hurt.

Blood tests help confirm the cause and assess overall risk. The usual set includes HbA1c, vitamin B12 (especially for people on metformin), kidney function, thyroid tests and a lipid profile.

Most people do not need a nerve conduction study. It is reserved for an unusual picture, such as numbness in one leg only or weakness that is progressing quickly.

How often should a person with diabetes have a foot examination?

The ADA Standards of Care recommend a full foot examination at least once a year for everyone with diabetes. Screening for neuropathy should begin at diagnosis in type 2 diabetes and about 5 years after diagnosis in type 1.

Feet that already show changes need closer follow-up. The intervals below reflect the general approach of the International Working Group on the Diabetic Foot (IWGDF). Your doctor will tailor them to you.

At every diabetes visit, take off your shoes and socks. Doctors are busy, and bare feet on the examination couch tend to get looked at.

Nerve damage that is already established rarely recovers fully. Progression, however, can be slowed, and symptoms can be controlled.

Tighter sugar control, particularly in the first years after diagnosis, slows further injury. Nerve pain usually improves with appropriate medicine. When low B12 is contributing, correcting it may bring partial relief. With consistent care, most people with neuropathy keep both feet intact and walk on them comfortably for many years.

Control of sugar, blood pressure and cholesterol

Everything else rests on stable blood sugar. For many adults the HbA1c target is around 7%, though it may be set higher or lower depending on age, other illnesses and the risk of low sugar episodes.

Blood pressure and lipids affect the small vessels that nourish the nerves, so they are treated with the same seriousness. Stopping cigarettes, bidi, gutkha, khaini and other tobacco benefits both nerves and circulation. For some patients,continuous glucose monitoring uncovers swings in sugar that fasting tests miss, which allows treatment to be adjusted more precisely.

Medicines for nerve pain

Common painkillers do little for neuropathic pain. Doctors generally use other drug groups instead, including medicines originally developed for seizures (pregabalin, gabapentin) and for depression (duloxetine, amitriptyline). Creams applied to the skin help some people.

These medicines reduce pain signalling. They do not heal the nerve. Drowsiness, dizziness and a dry mouth are common side effects, and some of these drugs are unsuitable for people with certain heart, kidney or eye conditions. The choice of medicine and dose is your doctor's decision, so avoid over-the-counter purchases and never take tablets prescribed for a relative.

Vitamin B12

Years on metformin can lower B12 levels in some patients, and the resulting deficiency can add to numbness. Periodic B12 testing is sensible for anyone on metformin, and more so when foot symptoms appear. A low level is easily treated. Metformin itself remains one of the most useful diabetes medicines, so do not stop it without speaking to your doctor.

Treatment of a diabetic foot ulcer

An ulcer needs medical treatment from the start. The first priority is to take pressure off the wound, using special footwear, a cast or rest, because an ulcer that is walked on will not heal. The wound is cleaned and dead tissue removed by a doctor or trained nurse, then dressed correctly. Antibiotics are used when there is infection, chosen to match it.

Blood supply to the foot has to be assessed, since no dressing can make up for poor circulation, and some patients need a vascular surgeon. Good sugar control throughout healing makes a real difference. Deep infection, infection of the bone or severely reduced blood flow may require hospital admission and a surgical team. In every case, earlier treatment means a better chance of saving the foot.

A daily foot routine takes about 5 minutes and prevents more ulcers than any medicine.

• Examine both feet every day, including the soles, heels and the spaces between the toes. Look for cuts, cracks, blisters, redness, swelling or colour change. Use a mirror, or ask someone at home to look if bending is difficult.
• Wash the feet in lukewarm water with mild soap. Test the water with your elbow before putting your feet in. Avoid long soaks.
• Dry carefully, especially between the toes.
• Apply a plain cream or oil to dry skin and cracked heels, keeping it out of the toe spaces.
• Trim toenails straight across after bathing, when they are soft, and smooth the corners with a file. If your eyesight or reach is limited, have someone help.
• Leave corns and calluses alone. Blades and acid corn plasters do more harm than good.
• Wear footwear at all times, inside the house as well.
• Use clean, dry socks without tight elastic or thick seams. Cotton works well in humid weather.
• Keep your feet away from fires, heaters, hot water bottles and heating pads.
• After rain, field or garden work, wash and dry the feet and change into dry footwear.

What kind of footwear is best for diabetic feet?

A good diabetic shoe has a closed toe, a firm heel counter that holds the back of the foot, and a deep, roomy front so the toes are not cramped. The inside should be smooth with soft lining and no hard seams, and the sole thick enough that a thorn cannot pass through. Velcro straps or laces allow adjustment on days when the feet swell.

Buy shoes in the evening, when the feet are at their largest. Break in a new pair gradually, an hour or two at a time, and check for red marks each time you take them off.

Thin rubber chappals are acceptable for a few minutes around the house but not for long walks or outdoor work. People with loss of sensation or a foot deformity may need custom footwear or moulded insoles, and their doctor can advise on these.

Many ulcers become serious through home treatment given with good intentions. Turmeric, toothpaste, herbal pastes and coffee powder can irritate the wound and hide signs of infection. Hot fomentation can burn skin that has lost feeling. Popping a blister or trimming the hard skin around a wound opens a path for germs.

Two mistakes come up again and again. The first is continuing to walk on a wound because it does not hurt. The second is starting leftover antibiotics, or buying them from a shop without a prescription, which can mask an infection without treating it properly.

The right first step is simple. Rinse the area gently with clean water, cover it with a clean dry dressing, keep weight off the foot, and have it seen by a doctor within a day.

"Walking barefoot keeps the feet healthy." For someone with diabetes and any loss of feeling, bare feet are one of the commonest routes to injury.

"Burning feet come from heat in the body." In a person with diabetes, burning soles far more often reflect nerve damage.

"A foot ulcer means amputation is coming." Most ulcers heal when treated early and correctly. The risk of losing a toe or a foot rises sharply with delay, not with the ulcer itself.

"Insulin harms the nerves." Insulin does not cause neuropathy. Prolonged high sugar does, and insulin, when it is needed, helps protect the nerves by bringing sugar down.

"Nerve pain tablets are addictive." Most medicines used for neuropathic pain are not habit-forming when taken as prescribed. Concerns about side effects are best raised with your doctor rather than settled by avoiding treatment.

The same long-term exposure to high sugar, high blood pressure and high cholesterol that injures the nerves of the feet also damages blood vessels in the heart, kidneys and eyes. A person with neuropathy or PAD is more likely to have, or to develop, heart disease, kidney disease and diabetic eye disease.

For that reason, a finding in the feet usually leads to checks elsewhere. Autonomic neuropathy can also disturb heart rate and blood pressure control, causing light-headedness when standing up or a fast pulse at rest. Mention these at your next visit.

Calf pain that comes on with walking and settles with rest, or sugar readings that have been creeping up, are also good reasons to book a visit. More on long-term care is on ourdiabetes care page.

Dr. Das examines the feet of people with diabetes as a routine part of their visits, with diabetic foot checks for sensation, pulses, skin and footwear done at the clinic. Findings are read together with your HbA1c, which is usually ready before you leave, and with your blood pressure and heart assessment. Family members are welcome to sit in, since they are often the ones who help with foot checks at home. You can read more on ourdiabetic foot care page.

• Diabetic neuropathy is nerve damage from long-term high sugar, and it usually begins in the toes of both feet.
• Reduced feeling allows small injuries to go unnoticed, which is how most diabetic foot ulcers start.
• A foot examination at least once a year is recommended for everyone with diabetes, more often once sensation or blood flow is reduced.
• Established nerve damage rarely reverses, but good control of sugar, BP and cholesterol, and stopping tobacco, slow its progress.
• A daily foot check and protective footwear, worn indoors and out, prevent most serious problems.