Diabetes and Wound Healing: Why Wounds Heal Slowly

Medically reviewed by Gerardo Sison, PharmD · Last updated

Key Takeaways

  • Diabetes can slow healing because high blood sugar, over time, damages nerves and blood vessels.
  • Your feet face the most risk because nerve damage can hide small injuries there.
  • Keeping a wound clean and covered, keeping pressure off it, and following your care team's plan can help it heal.
  • A foot ulcer that is not at least half smaller after four weeks of proper care needs a new look from your care team.
  • Heavy bleeding, bleeding that does not stop after 10 minutes of pressure, or a foot wound that turns black and smells bad needs emergency care.

High blood sugar, a central facet of diabetes, can damage the nerves and blood vessels essential to healing if left unchecked. Damaged nerves can keep you from feeling a small cut or blister on your foot, and damaged blood vessels let less blood reach the wound.

The wound can then stay longer in the early inflammation stage of healing. It also has a higher risk of infection. A chronic wound is one that stays open and does not heal as expected. Diabetes raises your risk that a wound turns chronic.

A foot ulcer is a sore on the foot. In people with diabetes, foot ulcers come before about four in five amputations of a toe, foot, or leg.

How Does Diabetes Slow Wound Healing?

High blood sugar from diabetes can damage nerves and blood vessels over time, and that damage slows healing. Nerve damage and poor blood flow then do much of the harm to a wound. High blood sugar can also weaken your defense against germs and keep a wound in an early stage of healing.

Nerve Damage Hides Small Injuries

Peripheral neuropathy is nerve damage that most often affects the feet and legs. Up to half of people with diabetes have it.

Over time, high blood sugar and high levels of fats in the blood can damage nerves. They can also damage the small blood vessels that feed the nerves.

Nerve damage can cause you to lose feeling in your feet. Without feeling, you may not notice a pebble in your sock. You may also miss a cut, blister, or sore. Small problems can become serious if they are not treated early.

A foot ulcer is often painless for the same reason.

Poor Blood Flow Slows Repair

High blood sugar can damage blood vessels over time. This damage can lower blood flow to your legs and feet.

Without enough blood flow, a sore or an infection can be hard to heal. Less oxygen can reach the wound. Fewer white blood cells, which fight germs, can reach it too.

Peripheral artery disease is a buildup of plaque in the arteries that lowers blood flow, most often to the legs and feet. About half or more of people with a diabetic foot ulcer have it.

Sometimes a bad infection never heals and can lead to gangrene. A foot infection that turns black and smells bad can be a sign of gangrene.

A Weaker Defense Against Infection

Diabetes can weaken your body's defense against germs. That raises your risk of a wound infection.

About half of diabetic foot ulcers become infected. A foot infection can spread quickly into deeper tissue. About one in five moderate-to-severe foot infections leads to an amputation.

Healing Stalls in the Inflammation Stage

Diabetic wounds can stay in the inflammation stage longer than other wounds.

A wound passes through the stages of healing, which overlap. They are clotting, inflammation, new tissue growth, and remodeling into a scar.

During inflammation, the body sends immune cells to the wound. A diabetic wound can be slow to move on to growing new tissue. This delay can lead to a chronic wound.

Why Do Diabetic Wounds Turn Chronic?

Diabetic wounds can turn chronic when nerve damage, poor blood flow, infection, or a long inflammation stage keeps them from healing. People with diabetes and obesity are at high risk of chronic wounds.

Diabetic foot ulcers are one of the main kinds of chronic wounds. Pressure sores and leg ulcers from vein problems are two other main kinds.

Gangrene and foot ulcers that do not get better with treatment can lead to an amputation. Diabetes is a leading cause of amputations that are not caused by an injury.

In one national US study of 2015 data, the rate of these amputations was more than 20 times higher in adults with diabetes.

Which Wounds Are Most at Risk?

Wounds on your feet are most at risk when you have diabetes. Nerve damage can hide small injuries there. Diabetes can also lower blood flow in the feet, which can slow healing.

About 1.6 million people in the United States get a diabetic foot ulcer each year. Up to about one in three people with diabetes get one during their lifetime.

Diabetic foot ulcers are partly caused by too much pressure on one part of the foot. A callus is a thick patch of rough skin from rubbing or pressure on the same spot. If you have nerve damage, a callus can turn into an ulcer.

Early signs of a foot wound can include:

  • A cut, sore, or blister
  • A red spot
  • A warm spot, which can be the first sign that a blister or ulcer is starting
  • A callus with dried blood inside it, which can be the first sign of a wound under it

People with diabetes also have a higher risk of wound problems after surgery. These can include infection or a surgical wound that opens back up.

How Can a Diabetic Wound Heal Faster?

A diabetic wound can heal faster when you treat it early, keep it clean and covered, and keep pressure off it. Keeping your blood sugar in range and getting professional care can also help.

Treat New Cuts and Blisters Right Away

Treat a new cut or blister right away. Prompt first aid can help prevent infection and speed healing.

For a minor cut, take these steps in order:

  1. Wash your hands with soap and water.
  2. Wash the cut well with mild soap and water.
  3. Press on the cut to stop the bleeding.
  4. Put on antibacterial ointment and a clean bandage that will not stick.

Foot wounds often become infected in people with diabetes. Cover a blister, cut, or sore on your foot with a bandage.

Call your care team right away if a cut, blister, or bruise on your foot does not start to heal after a few days.

Keep the Wound Clean, Covered, and Moist

Keep a foot ulcer clean and covered with a bandage, as your care team directs. Clean the wound every day, or as often as your care team advises.

Your care team will choose the dressing, which is the covering on the wound. The right dressing controls extra fluid and keeps the wound moist.

Keep the skin around the ulcer from getting too wet. Wash your feet, but do not soak them.

Take Pressure Off the Wound

Taking pressure off a foot ulcer can help it heal faster. This is called offloading.

Sometimes even a few minutes of pressure on a healing ulcer can undo the healing so far.

Your care team may give you special shoes, a brace, or a special cast. You may need a wheelchair or crutches until the ulcer heals.

For a sore on the bottom of the foot caused by nerve damage, guidelines prefer a knee-high cast or boot you cannot remove. However, for those with an infection or already poor blood flow, a removable boot may be recommended. Try to keep weight off the ulcer while it heals.

Keep Your Blood Sugar in Range

Keeping your blood sugar in your target range may help you heal. It can also help your body fight infection.

Some diabetes medicines lower blood sugar. Your care team can explain your options for lowering your blood sugar.

One analysis of people with foot ulcers tied a higher A1C level to a higher risk of amputation. It found no clear link between A1C level and whether the ulcer healed. Your care team sets the target range that fits you.

Stop Smoking and Keep Blood Flowing

Smoking lowers blood flow to your feet. Nicotine can also raise blood sugar. People with diabetes who smoke are more likely to have complications, including amputation.

After you quit, your circulation can improve within two weeks to three months.

You can also help blood flow to your feet with these daily habits:

  • Put your feet up when you sit.
  • Wiggle your toes and move your ankles for a few minutes through the day.
  • Avoid tight socks, and do not hold up socks with rubber bands.
  • Stay active in ways that keep weight off an open foot ulcer.

Eat Enough to Heal

Healing raises your body's nutritional needs. Poor nutrition can slow healing. Eat enough food while your wound heals.

Vitamin, mineral, and protein supplements have not been shown to help foot ulcers heal. Ask your care team before taking any supplement.

Get Professional Wound Care

Professional care for a foot ulcer rests on five basic steps:

  • Taking pressure off the ulcer
  • Removing dead tissue
  • Restoring blood flow when needed
  • Treating infection
  • Using the right dressings

Removing dead tissue is called debridement. A provider, such as a foot doctor, does it. Never try to do it yourself. The ulcer may look bigger and deeper afterward.

Your care team may prescribe antibiotics if the wound is infected.

If poor blood flow is likely, your care team may refer you to a blood vessel specialist. Delays in this care can lead to more tissue loss.

If an ulcer does not heal with standard care, your care team may consider other treatments. One is negative pressure therapy, which uses a sealed dressing attached to a vacuum pump. International guidelines suggest it mainly for wounds after foot surgery. Others are some skin substitutes and oxygen applied to the wound.

Hyperbaric oxygen therapy can deliver more oxygen to the wound. It may be considered as an added treatment for ulcers with poor blood flow that have not healed with standard care.

What Should You Avoid?

While a diabetic wound heals, avoid these things:

  • Soaking your feet
  • Walking on an open foot ulcer without the shoe, boot, or cast your care team gives you
  • Cutting corns or calluses yourself
  • Using corn or callus removers
  • Going barefoot, even indoors
  • Putting a heating pad or hot water bottle on your feet
  • Putting antiseptic dressings on a foot ulcer unless your care team chooses them
  • Putting honey, bee products, or herbal products on a foot ulcer

How Can You Tell If a Wound Is Not Healing?

One sign a wound is not healing well is a cut, blister, or bruise on your foot that does not start to heal after a few days. Call your care team right away if this happens.

If a foot ulcer is not at least half smaller after four weeks of proper care, guidelines call for your care team to consider advanced treatments. They should also look again at what is slowing healing.

If an ulcer shows no sign of healing after four to six weeks of good care, your care team may consider imaging of the blood vessels. They may also consider restoring blood flow.

Even with good care, a foot ulcer can take weeks to months to heal. About three or four in 10 heal within 12 weeks. Nearly one in four is still open after a year.

How Can You Prevent New Wounds?

Checking and caring for your feet every day can help prevent new wounds. It helps you catch problems early and get them treated. Early treatment can greatly lower your risk of amputation.

Check your feet every day, including between your toes. If you cannot see the bottoms of your feet, use a mirror or ask a family member to help. If you care for someone with diabetes, you can do this check for them.

A daily routine can include these elements of a foot care regimen:

  • Wash your feet in warm, not hot, water, and do not soak them.
  • Dry your feet well, especially between the toes.
  • Put lotion on the tops and bottoms of your feet, but not between the toes.
  • Trim your toenails straight across and smooth the edges with a nail file.
  • Wear socks and shoes that fit well.
  • Check inside your shoes before you put them on.

See a foot doctor for nail trims if you cannot see, feel, or reach your feet.

Have your feet checked at every care visit. See a foot doctor at least once a year, and more often if you have nerve damage.

When Should You Call a Doctor?

Call your care team right away if you see signs of infection around a wound. Do not wait for your next appointment.

Watch for these signs:

  • Redness, warmth, or swelling around the wound
  • More drainage than before
  • Pus
  • A bad smell
  • More pain
  • Firmer skin around the wound
  • A red streak spreading from the wound
  • An ulcer that looks very white, blue, or black
  • Fever or chills

Call 911 if a wound bleeds heavily or does not stop bleeding after 10 minutes of pressure.

Get emergency care right away if a foot wound turns black and smells bad, which can be a sign of gangrene.

Frequently Asked Questions

How Long Does a Diabetic Wound Take to Heal?

A diabetic wound such as a foot ulcer can take weeks or even several months to heal. About three or four in 10 diabetic foot ulcers heal within 12 weeks. If an ulcer is not at least half smaller after four weeks of proper care, your care team should check it again.

Should Diabetic Wounds Be Covered?

Yes, diabetic wounds should be covered with a clean bandage or the dressing your care team chooses. The dressing should keep the wound moist while the skin around it stays dry.

Which Ointment Is Good for Diabetic Wounds?

Which ointment is good for a diabetic wound depends on whether it is a fresh minor cut or a foot ulcer. For a fresh minor cut, antibacterial ointment and a clean bandage that will not stick are standard first aid. For a foot ulcer, ask your care team before putting any ointment on it.

Does Honey Help Diabetic Wounds Heal?

Some small studies suggest honey dressings may help diabetic foot ulcers heal, but the evidence is too limited for guidelines to recommend them. Guidelines advise against putting honey or bee products on a diabetic foot ulcer. Ask your care team before putting any home remedy on a wound.

Sources

This article is for general information only and is not medical advice.