Diabetic foot gangrene and black toes: can the foot be saved?

A toe that has turned dark red, purple or black is frightening, and in a person with diabetes it should be treated as urgent. This guide explains what gangrene is, when to seek emergency care, whether a foot with gangrene can be saved or whether it always means amputation, how doctors decide, and what to ask before agreeing to any operation.

When is diabetic foot gangrene an emergency?

If you think you have gangrene, go to an emergency department or call your local emergency number. In the UK, NHS advice is to call 999 or go to A&E immediately. The NHS lists a body part turning dark red, purple or black, and pain that gradually gets worse or suddenly becomes severe, among the symptoms (NHS, gangrene). MedlinePlus adds foul-smelling discharge from a wound, and advises contacting your provider right away if skin turns blue or black (MedlinePlus, gangrene).

Signs that a foot infection has become serious include (IWGDF/IDSA 2023):

• a black, very dark or dead area of tissue (necrosis or gangrene);
• redness that spreads more than about 2 cm from the wound or is spreading quickly;
• fever, chills, confusion or very low blood pressure, which can mean the infection is affecting the whole body;
• a crackling feeling under the skin, blisters, or new numbness or new localised pain at the wound;
• a wound that keeps getting worse even though you are taking antibiotics.

These signs call for urgent assessment. The IWGDF/IDSA guideline advises urgent surgical consultation for severe infection, or for moderate infection complicated by extensive gangrene, necrotizing infection, a deep abscess or severe lower-limb ischaemia (IWGDF/IDSA 2023). Do not wait to see whether it improves, and do not try to treat it at home.

What is diabetic foot gangrene, and what does a black toe mean?

Gangrene is the death of body tissue. The IWGDF defines diabetes-related foot gangrene as a condition that occurs when body tissue dies because of insufficient blood supply, infection or injury (IWGDF/ESVS/SVS 2023). In people with diabetes it often follows reduced blood flow, infection, or both. The NHS notes that gangrene can happen as a complication of diabetes or of conditions that affect circulation (NHS, gangrene).

Doctors often describe two forms. Many cases of dry gangrene are not infected. Wet gangrene is considered to be always infected, and it is the most dangerous type because, if left untreated, it can lead to sepsis. Dry gangrene that becomes infected can progress to wet gangrene (MedicineNet, gangrene). That is why wet gangrene of the foot is treated as an emergency.

Colour change alone cannot tell you what is going on. A toe that is dark red, purple or black may be gangrene, but only an examination, together with tests of blood flow and infection, can tell. In a person with diabetes, treat any new black or very dark area as urgent until a clinician has seen it.

Doctors may describe gangrene limited to part of the forefoot as Wagner grade 4 and gangrene of most of the foot as grade 5. Our guide to the Wagner classification explains what the grades mean, and our pages on Wagner grade 4 and Wagner grade 5 describe those stages in more detail.

Can a foot with gangrene be saved, or does it always mean amputation?

Often the foot can be saved, but the gangrenous tissue itself cannot. Dead tissue does not come back: MedlinePlus notes that it should be removed so that the surrounding living tissue can heal (MedlinePlus, gangrene). Depending on the case, it is removed surgically, or it separates on its own, which is called auto-amputation. The realistic question is therefore usually whether a major amputation (above the ankle) can be avoided and a working foot kept. The goal of limb salvage is to remove what is dead or infected and keep the part of the foot that is still alive working, with enough blood supply to heal.

Whether the foot can be saved depends mainly on blood supply, how far infection has spread, how much tissue is still alive, and the person's overall health.

Research gives a realistic picture. A prospective study followed 476 people with Wagner grade 4 forefoot gangrene, treated by a multidisciplinary team at one university diabetic foot centre in Sweden between 2000 and 2012; 64% had a vascular intervention. Of all participants, 42% healed without a major amputation (11% after auto-amputation and 31% after a minor amputation below the ankle), 22% healed after a major amputation, and 34% died before their wound healed. Healing in this cohort always involved losing some tissue. The participants were older (median age 73), 82% had cardiovascular disease, and the median time to healing was 41 weeks (Elgzyri et al., 2021).

Sometimes a major amputation is the safest choice. The IWGDF guideline advises against revascularisation when there is no realistic chance of wound healing, when major amputation is inevitable, or when a functional foot is unlikely. It says the decision to proceed to primary amputation should be made together with the person and a multidisciplinary team, including a vascular specialist, unless an emergency procedure is needed (IWGDF/ESVS/SVS 2023).

What tests decide whether the foot can be saved?

Two questions drive the decision: is there enough blood flow to heal, and how far has infection spread?

• Blood flow. A pulse examination, ankle-brachial index, toe pressure and Doppler waveforms. If toe pressure cannot be measured, transcutaneous oxygen pressure (TcPO2) or skin perfusion pressure can be used instead. Signs of severe ischaemia, for example a toe pressure below 30 mmHg, should trigger an urgent consultation with a vascular specialist about possible revascularisation (IWGDF/ESVS/SVS 2023).
• The arteries. When revascularisation is being considered, the guideline recommends evaluating the whole arterial circulation of the leg, from the aorta to the foot, with detailed views of the arteries below the knee and in the foot (IWGDF/ESVS/SVS 2023).
• Infection. Examination, blood inflammatory markers such as CRP, a probe-to-bone test and X-rays, with MRI when the diagnosis of bone infection remains in doubt after those first tests (IWGDF/IDSA 2023). See also our guide to bone infection in the diabetic foot.
• Staging the limb threat. The Global Vascular Guidelines endorse the Wound, Ischemia and foot Infection (WIfI) system to stage how severely the limb is threatened, and prefer toe pressures for objective blood-flow testing (Conte et al., 2019).

Guidelines also say who should be involved. Anyone with suspected chronic limb-threatening ischaemia, meaning poor blood flow together with rest pain, gangrene or an ulcer that has not healed for more than two weeks, should be referred urgently to a vascular specialist (Conte et al., 2019). A person with diabetes, peripheral artery disease and a foot ulcer or gangrene should be treated by a multidisciplinary team as part of a comprehensive care plan (IWGDF/ESVS/SVS 2023).

What limb-salvage options exist for diabetic foot gangrene?

Options depend on the cause. They are listed here with what the main guidelines say. The strength of the evidence differs a lot from one option to the next.

• Restoring blood flow (revascularisation). The IWGDF/ESVS/SVS guideline recommends considering revascularisation when ischaemia is present, with an urgent vascular consultation when infection or gangrene is present. For people who have a suitable vein and are suitable for either approach, it suggests considering bypass in preference to endovascular treatment (conditional recommendation, moderate certainty). It advises treatment in centres with expertise in, or rapid access to, both approaches (IWGDF/ESVS/SVS 2023).
• Removing infected and dead tissue, with antibiotics. This may include drainage, debridement or a minor amputation. For moderate and severe infections, early surgery within 24 to 48 hours may be considered (conditional recommendation, low certainty) (IWGDF/IDSA 2023). When there is an abscess that needs immediate drainage, or gangrene that must be removed to control the infection, the PAD guideline says immediate surgery should be considered first, with broad-spectrum antibiotics. Once the infection is controlled, the arteries should be assessed with a view to prompt revascularisation (IWGDF/ESVS/SVS 2023).

Beyond restoring blood flow and removing infected or dead tissue, specialist centres may use additional wound therapies. Negative pressure wound therapy (NPWT) applies a vacuum dressing to help some wounds heal, particularly after surgery. Hyperbaric oxygen therapy delivers extra oxygen and is used as an add-on for some ischaemic wounds. Tibial cortex transverse transport (TCT), a bone-surgery technique used mainly in China, is offered at some centres as part of limb-salvage care, and stem-cell and other cell-based therapies are used at some specialist centres.

Which of these, if any, is appropriate depends on your arteries, infection, overall health and where you are treated. A multidisciplinary team should be able to explain why each option is or is not suitable for your specific case.

What should you ask before agreeing to amputation?

If an amputation has been recommended, it is reasonable to ask:

• Has my blood flow been measured (toe pressure, ankle-brachial index or TcPO2), and has a vascular specialist reviewed my arteries?
• Is there an infection that needs urgent surgery, and what is the plan if I do not have the operation today?
• At what level is the amputation proposed, why that level, and could a smaller operation be enough?
• What outcome should I expect from trying to save the foot compared with amputation, including healing time, the chance of further surgery and my ability to walk?
• Which team will look after the wound and the rest of my foot, and who can review my records for a second opinion?

These questions are not a way to delay surgery that is urgently needed. The PAD guideline warns that delay in treatment can lead to rapid tissue destruction (IWGDF/ESVS/SVS 2023). They are a way to make sure the decision rests on a full assessment.

When should you get a second opinion?

A second opinion is worth seeking if you have been told that nothing can be done, if no vascular assessment has been done, or if you are unsure about the recommended operation.

The PAD guideline notes that lack of access to specialist care is associated with worse foot outcomes, and says referral pathways, including virtual ones, are essential in rural and remote areas where specialist access is difficult (IWGDF/ESVS/SVS 2023).

If you would like a remote review of your records, DFU Care China offers a free review by a multidisciplinary specialist team, and we will tell you honestly if we do not think treatment in China would help in your situation. Delay can lead to rapid tissue destruction, so if you have any of the warning signs above, go to emergency care first and contact us afterwards. You can read more about how a second opinion works and about alternatives to amputation, or share your wound photos and reports on WhatsApp to start.

Frequently asked questions

Can gangrene go away on its own?

Dead tissue does not recover. In some cases the gangrenous tissue separates by itself, which is called auto-amputation, and 11% of all participants in the cohort above healed this way. They were managed by a multidisciplinary foot team, 64% of the cohort had a vascular intervention, and healing after auto-amputation took a median of 48 weeks (Elgzyri et al., 2021). This is not a reason to wait at home: the underlying cause, whether poor blood supply, infection or injury, still has to be found and treated (IWGDF/ESVS/SVS 2023).

How dangerous is wet gangrene?

Wet gangrene is infected, and it is described as the most dangerous type of gangrene because, if left untreated, it can lead to sepsis (MedicineNet, gangrene). You cannot tell dry from wet gangrene reliably at home, so treat any spreading dark area, discharge or fever as an emergency.

What is the difference between dry and wet gangrene?

The difference between dry and wet gangrene is whether infection is present. Dry gangrene develops when tissue loses its blood supply but is not infected; the affected part, often a toe, turns dark and dries out slowly. Wet gangrene is infected, can spread quickly, and is described as the most dangerous type because it can lead to sepsis if untreated (MedicineNet, gangrene; NHS, gangrene). A dry gangrene toe that becomes infected can turn into wet gangrene. Because you cannot reliably tell them apart at home, treat any black toe, spreading darkness, discharge or fever in a diabetic foot as an emergency.

What are the early signs of gangrene in the feet?

Early signs of gangrene in the feet include skin that turns dark red, purple, blue or black, pain that gets worse, and an area that becomes cold or numb; in wet gangrene there may also be swelling, a foul-smelling discharge or fever (NHS, gangrene; MedlinePlus, gangrene). In a person with diabetes, nerve damage can blunt the pain, so a change in colour may be the first sign. Any of these symptoms of gangrene in the feet needs urgent assessment rather than waiting to see whether it improves.

Does a black toe always mean a major amputation?

No, but it usually means losing the dead tissue. A black toe needs urgent assessment, and what happens next depends on blood flow, infection and how much tissue is affected. In the Wagner grade 4 cohort above, 42% of all participants healed after auto-amputation or a minor amputation, for example of a toe, and 22% healed after a major amputation (Elgzyri et al., 2021). The realistic aim is usually to keep a working foot, even if the dead toe is lost.

This article is for educational purposes. Every patient's situation is different. The information here is general guidance, not a substitute for professional medical advice. Always consult a qualified healthcare professional about your specific case.