Thursday, June 01, 2023
DIABETES Diabetic Infections

Why Do Diabetics Develop Foot Gangrene? is a participant in the Amazon Services LLC Associates Program. As an Amazon Associate, I earn from qualifying purchases. Read full Disclosure here.

Diabetes can cause several foot problems. When there is long-standing hyperglycemia (elevated blood sugar levels), this can affect the sensation in your feet. This places you at higher risk for injury.

Not only that, elevated blood sugar levels can cause peripheral vascular disease. These factors can cause diabetics to develop foot gangrene. 

black lesions foot

There are 3 types of gangrene: 

  • Dry Gangrene
  • Wet Gangrene
  • Gas Gangrene 

In this article, we will break down the different types of gangrene, what causes it, as well as treatment. 

We will also discuss what preventative measures you can take to make sure you don’t develop gangrene in the feet. 

Let’s dive in…

What Is the Cause of Dry Gangrene in the Diabetic Foot?

Dry gangrene occurs when the tissue in the foot dies due to inadequate blood supply. This can occur gradually. When someone has diabetes, elevated blood sugar levels can affect the blood vessels that supply blood to the feet. The blood vessels can become hardened and narrow. This restricts blood flow to the feet. A good number of diabetics have peripheral vascular disease. 

The tissues in the feet need to be properly perfused. If there is a blockage in the blood vessels, then the tissues will die, causing dry gangrene. This is often seen in the toes of the feet. If you have other risk factors for peripheral vascular disease such as high cholesterol or smoking, your risk for dry gangrene is higher. 

man with pain in foot

What Are the Symptoms of Dry Gangrene?

  • Intermittent Claudication

When someone has a significant blockage in their feet, they may feel a cramping-type pain in their thighs, legs, and feet. You may feel cramping pain when you are walking and may be forced to stop and sit down. This is called “intermittent claudication”. You may also even start to feel cramping pain in the legs during rest. This is suggestive of severe peripheral vascular disease. 

  • The Skin on Your Feet May Feel Cold and Pale

When there is limited blood flow in the feet, the feet will feel cold and the skin will look pale. 

  • Hair Loss

With peripheral vascular disease, hair growth can be affected. You may notice slower hair growth in the toes of your feet or no hair growth at all. 

  • Swelling and Pain in the Feet

Gangrene can be very painful. However, some people may not feel any pain due to neuropathy.

  • Purple, Blue, or Black Discoloration of the Skin

With tissue death, you may notice a purple and blue color on your feet, followed by black color. The skin can feel hard and shrunken. 

  • Inability to Walk

If you have severe gangrene, you may feel like your foot is numb. Due to extensive tissue death, you may not be able to move your foot and walk. 

How Is Dry Gangrene in the Foot Treated?

Due to tissue death, dry gangrene can usually be treated with auto-amputation. Auto-amputation occurs when the affected gangrenous portion of the foot spontaneously falls off. This may take months to happen. As long as the pain is managed and there is no superimposed infection, auto-amputation is acceptable. 

Your doctor will perform a thorough physical exam. Your doctor will be checking the pulses in your feet (Dorsalis Pedis and Posterior Tibial Pulses). These two pulses supply blood flow to the feet.

The pulses may be diminished or absent in dry gangrene. In some cases though, the foot pulses may be palpable, but blood flow may be blocked closer to the toes. This can cause the toes to turn black. 

If your doctor cannot feel the pulses in your feet, he/she will order an Ankle Brachial Index (ABI) test. This is a non-invasive painless test that can be done to check the circulation in your feet. 

Your doctor may also order an Arterial Duplex Ultrasound which can provide more information about which vessels are blocked in the legs/feet. 

If you have significant blockage in your feet, your doctor will refer you to a vascular surgeon. Your vascular surgeon may need to perform surgery to help replenish blood flow in the legs and feet. This can be done with a stent or bypass. 

It’s very important to address any blood flow issues in the feet so that the gangrene does not spread. Even if auto-amputation occurs, good blood flow is still needed to heal the amputation site.

You should keep the gangrenous tissue clean by applying Betadine to the area. Betadine is an antiseptic and will keep the tissue dry.

Your doctor may also place you on antibiotics to prevent the tissue from becoming infected. 

However, if the gangrene is extremely painful, it would not be feasible to wait months for auto-amputation. In these cases, surgery would be needed. 

Your doctor will perform surgery under anesthesia to amputate the affected portion of the foot. You will need to be in a cast boot after the procedure for a few weeks. Depending on what is amputated (the toes or the feet), your doctor will instruct you on whether you can bear weight on the foot or not. 

What Is the Cause of Wet Gangrene in the Diabetic Foot?

Wet gangrene is essentially dry gangrene that becomes infected. Wet gangrene can spread quickly and is a limb-threatening infection. Wet gangrene can also form from burns and frostbite injuries. It is important to address wet gangrene quickly. 

What Are the Symptoms of Wet Gangrene in the Diabetic Foot?

  • Purple, Blue, and Black Discoloration of the Skin
  • Pain
  • Foul Odor 
  • Blisters
  • Pus 
  • Fever
  • Lightheadedness
  • Increased Respiratory Rate and Heart Rate

How Is Wet Gangrene Treated?

Your doctor will perform a thorough physical exam. Your doctor will order x-rays as well as an MRI to evaluate the extent of tissue and bone damage. Your doctor will also assess the blood flow in your feet by ordering arterial testing. 

Your doctor will obtain a wound culture to determine what bacteria are present in the wound.

You will need to be admitted to the hospital to receive strong IV antibiotics. 

Surgery is indicated to treat wet gangrene and control the infection. Your doctor will suggest amputating the dead tissue in the foot. This will be done under anesthesia. Your doctor will remove necrotic tissue in the foot until healthy tissue is visible. This is of utmost importance because wet gangrene can spread quickly if not treated completely. 

While in surgery your doctor will obtain samples of the gangrenous tissue as well as the bone to determine the organism present. This will help dictate which antibiotics will work best to clear the infection. If a bone infection is present, you may need IV antibiotics for 6 weeks. 

To read more about Diabetic Bone Infections In The Foot, check out this supplemental post. 

Diligent wound care will be required after the surgery. In most cases, if extensive amputation is done, you may have to remain off of your feet for several weeks in a cast boot after surgery until the foot heals. 

What Is the Cause of Gas Gangrene in the Diabetic Foot?

Like wet and dry gangrene, gas gangrene can occur in diabetics due to injury secondary to numbness, and lack of blood flow. However, gas gangrene can turn into a life-threatening infection if not addressed immediately.

In gas gangrene, a bacteria called Clostridium perfringens produces toxins and gas in the tissues. This can lead to extensive tissue loss. Gas gangrene can spread quickly.

What Are the Symptoms of Gas Gangrene in the Foot?

  • Air in the Tissues
  • Crackling Noise When the Foot Is Pressed On
  • Blue, Purple, Brown, and Black Discoloration of the Skin
  • Foul Smell on the Foot
  • Blisters
  • Foot Swelling
  • Systemic Signs of Infection Such as Fevers, Chills, Nausea, Lightheadedness
surgery instruments

How Is Gas Gangrene Treated?

IV antibiotics and surgical resection with amputation of dead tissue are required for gas gangrene. Your doctor will work quickly to remove dead tissue in the foot to control the infection and salvage as much of the foot as possible. 

The infection in gas gangrene can spread quickly. If it is not treated quickly, the patient may develop shock and even die. 

After surgical resection, daily wound care will be required to make sure the wound is healing appropriately. You will need to remain non-weight bearing in a cast boot until your doctor clears you to walk. If extensive amputation is done, you will need a prosthetic as well as diabetic shoes.  

Your doctor will manage any pain you have after surgery with pain medications. Phantom pain from an amputation can last up to 6 months after surgery. However, phantom sensation from limb loss can last up to 2 years. 

doctor performs foot exam

How Can Diabetics Prevent Dry Gangrene?

It’s very important to visit your local foot doctor regularly. If you are at high risk for developing gangrene due to numbness in your feet, you should see your foot doctor every 2-3 months. 

Your foot doctor will perform a diabetic foot exam and assess your blood flow. He/she will address any foot issues early on. 

It’s also important to pay attention to symptoms associated with poor blood flow, such as cramping in your feet. If you smoke, it’s important to try to quit smoking. It’s also important to follow a healthy diet to reduce the risk of high blood glucose levels. 

Gentle massages can help improve circulation in the legs. Make sure you are not wearing compression stockings if you have peripheral vascular disease. This can limit blood flow and cause pain. 

Make sure to check your feet daily for any cuts and bruises. Check your feet for skin changes. If you notice purple, red, blue, or black discoloration in your feet, call your doctor immediately. 

Avoid walking barefoot and make sure to wear protective diabetic socks and shoes. You cannot spread gangrene from person to person. 


In conclusion, diabetics with neuropathy and peripheral vascular disease are at increased risk for developing gangrene in the foot. Foot exams should be done regularly to prevent gangrene from occurring in the first place. Gangrene can spread rapidly and can be limb and life-threatening. It should be addressed quickly to ensure the best possible outcomes.

Related articles: Diabetic Neuropathy in the feet- A Simple Treatment Guide

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gangrene pin


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Vaishnavi Bawa
Dr. Vaishnavi Bawa is a Podiatrist who specializes in treating foot and ankle pathology. LifesLittleSteps mission is to educate the public about foot health in an easy-to-understand manner using evidence-based medicine.
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