Condition
Diabetic foot infections: signs, severity and when surgery helps
An infection of the skin, deeper tissue or bone of the foot in a person with diabetes, usually starting in a wound.
Medically reviewed by Dr. Efe Ozturk · Last reviewed
Watch: Diabetic foot infections: signs, grades and when surgery helps
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Most foot infections in people with diabetes start at a break in the skin, usually a diabetic foot ulcer. Foot infection is the most common event that leads to an amputation, so early treatment matters. Every open wound carries bacteria; infection means they have invaded the tissue. Untreated, infection can spread along tendons and between the foot’s compartments into joints and bone, sometimes quickly. In one large study, about one in five people with a foot infection also had a bone infection, called osteomyelitis. A wound counts as infected when at least two of these are present: swelling or firmness, redness, tenderness or pain, warmth, or pus. The redness has to reach more than half a centimeter beyond the wound edge. Nerve damage, poor circulation and a weaker immune response can each mask these signs. About half of people with a foot infection have a normal white blood cell count. Infections are graded mild, moderate or severe, and the risk of a hospital stay or an amputation rises with the grade. A mild infection stays in the skin and the fat beneath, and can almost always be treated without a hospital stay. A moderate one has redness of 2 centimeters or more, or reaches tendon, muscle, joint or bone. A severe infection brings two or more whole-body signs, such as fever, a fast heart rate or fast breathing, and hospital care is usually advised. The exam checks how far the redness reaches, how deep the wound goes, and whether a gentle probe touches bone. Because the exam can miss poor circulation, we also do noninvasive circulation testing at our practice. For cultures, a tissue sample from the cleaned wound identifies the germs more accurately than a surface swab. We take X-rays at our practice, arrange MRI at an outside imaging center, and when needed, Dr. Ozturk performs bone biopsies. Treating the infection alone makes failure much more likely, so care has several parts. When an infection needs antibiotics, we start them promptly and adjust them once culture results are back. Removing dead tissue, called debridement, and taking pressure off the wound both count. So do restoring circulation when needed and controlling blood sugar. While the wound heals, we usually see you every week or two to clean and measure it. A collection of pus, especially one under pressure, needs to be opened and drained promptly, usually within 24 hours. Dr. Ozturk performs these operations, draining the pus and removing dead and infected tissue. In one study of 112 hospital patients, prompt surgery went with about half as many above-ankle amputations as antibiotics alone for the first three days. Studies like this looked back at past records, so the evidence is low-certainty, but surgery needed to control a spreading infection shouldn’t wait. With the right care, most of these infections can be treated successfully, though closing the wound itself often takes months. See us within a day or two for any foot wound that isn’t healing, especially if you have diabetes. If a wound becomes red, warm, swollen or painful, or starts to drain, call us that day. For redness that spreads quickly or comes with fever, a cold, pale or blue foot, or black tissue, call 911 or go to the emergency department. Dr. Ozturk, a Foot and Ankle Surgeon board certified in wound care, treats foot wounds in Lyndhurst, Paramus and Millburn. To learn more, visit our website, or call the office to arrange a visit.
General education only; not a substitute for individual medical advice.
What a diabetic foot infection is
Most foot infections in people with diabetes start at a break in the skin, usually a diabetic foot ulcer. Every open wound carries bacteria; infection means they have invaded the tissue. Foot infection is one of the most frequent reasons people with diabetes need a hospital stay and the most common event that leads to an amputation, so early treatment matters.[1]
Untreated, infection can spread along tendons and between the foot’s compartments into joints and bone, sometimes quickly.[1] In a two-year study of 1,666 people with diabetes, 9.1% developed a foot infection, nearly always starting in a wound or a puncture wound. About one in five of those infected had a bone infection (osteomyelitis).[6]
Who is most at risk
In that study, infection was more likely when a wound reached bone, had been open more than 30 days, kept coming back or was caused by an injury, and when leg arteries were narrowed.[6] Long-term kidney failure raises the risk too.[1]
Poor circulation (peripheral artery disease) counts twice: it makes infection more likely and harder to overcome, so blood flow should be checked as soon as an infection is found.[1]
Signs to watch for, and why they can be quiet
A wound counts as infected when at least two of these are present: swelling or firmness, redness reaching more than half a centimeter beyond the wound edge, tenderness or pain, warmth, or pus.[1] An infected area that turns black and smells bad can be a sign of gangrene.[7] If that happens, go to the emergency department or call 911 (more on dark or black toes).
Nerve damage (peripheral neuropathy (external site)), poor circulation and a weaker immune response can each mask these signs. Fever and chills are uncommon, but when they appear they signal a more serious infection. So do redness that spreads quickly, a racing heart, fast breathing or blood sugar that suddenly runs high.[1]
An active Charcot foot, gout, a fracture or a blood clot can also make a foot red, warm and swollen.[1] Our guide to a red, hot, swollen foot explains the differences.
How severe is it? The infection grades
The grading scale, from the International Working Group on the Diabetic Foot (IWGDF) and the Infectious Diseases Society of America (IDSA), guides where and how you are treated.[1]
| Grade | What it looks like | What it usually means |
|---|---|---|
| Mild | Signs only in the skin and the fat beneath; any redness reaches less than 2 cm from the wound | Can almost always be treated without a hospital stay |
| Moderate | Redness 2 cm or more, or infection in tendon, muscle, joint or bone; no whole-body signs | Many can be treated as outpatients unless poor circulation or other illnesses add risk; early surgery considered |
| Severe | Two or more whole-body signs, such as fever, fast heart rate or fast breathing | Hospital care usually advised, with an urgent surgical opinion |
When the infection has reached bone, “(O)” for osteomyelitis is added to the grade.[1]
How a foot infection is evaluated
The exam checks how far the redness reaches, how deep the wound goes and whether a gentle probe touches bone. It can miss poor circulation, so blood flow should also be checked with noninvasive circulation tests. Blood tests for inflammation help when the picture is unclear.[1]
For cultures, the guideline prefers a tissue sample from the cleaned wound, taken by scraping or biopsy, over a surface swab, because it identifies the germs more accurately.[1] For suspected bone infection, the usual first steps are the probe test, X-rays and blood tests, with MRI if doubt remains. A bone sample is the accepted standard for confirming it.[1] We take X-rays and do noninvasive circulation testing at our practice. When needed, Dr. Ozturk performs bone biopsies, and we arrange MRI at an outside imaging center.
Antibiotics and wound care: the foundation
About half of diabetic foot ulcers aren’t infected when first seen. The guideline advises against antibiotics for these: they haven’t been shown to help healing or prevent infection, and they carry side effects and resistance risks.[1]
For a skin and soft tissue infection, the guideline recommends 1–2 weeks of antibiotics, possibly up to 3–4 weeks when a large infection is improving slowly or circulation is badly reduced.[1] When an infection needs antibiotics, we start them promptly and adjust them once culture results are back.
Removing dead tissue (debridement), taking pressure off the wound, restoring circulation when needed and controlling blood sugar all count. Treating the infection alone makes failure much more likely.[1] While the wound heals, we usually see you every week or two to clean and measure it (see wound care visits).
The guideline suggests not using hyperbaric oxygen or negative-pressure wound therapy just to treat an infection.[1] Once the infection is under control, the IWGDF wound-healing guideline gives conditional support to negative-pressure wound therapy for wounds left after surgery, and to hyperbaric oxygen for some ulcers with poor circulation that good standard care hasn’t healed.[8] For the wounds that need them, we use negative-pressure wound therapy and refer you for hyperbaric oxygen therapy.
When surgery is the step that saves the foot
A collection of pus, especially one under pressure or alongside dead tissue, needs to be opened and drained promptly, usually within 24 hours.[1] Any severe infection needs an urgent surgical opinion, as does a moderate one with extensive gangrene, a tissue-destroying (necrotizing) infection, a deep abscess, rising pressure inside the foot (compartment syndrome) or severely reduced blood flow.[1]
Among 112 hospital patients with a diabetic foot infection, those operated on promptly needed an above-ankle amputation about half as often (13% versus 27.6%) as those given only intravenous antibiotics for the first three days. Their hospital stays were also at least six days shorter.[3] In 106 people with diabetes and a deep foot abscess, delayed surgery (about six days on average) went with a higher amputation level. The longer the wait, the higher the level tended to be.[4]
Surgery drains pus and removes dead and infected tissue. If infected bone has to be removed, the guideline favors taking a limited amount and avoiding amputation where possible, with bone sent for culture.[1] Dr. Efe Ozturk, a Foot and Ankle Surgeon who is also board certified in wound care (FAPWH), performs these operations and, once the infection is controlled, can correct the foot shape that let the wound form.
With poor circulation as well, the guideline calls for urgent input from both a surgeon and a vascular specialist.[1] We coordinate with vascular specialists, who restore blood flow; see revascularization.
Surgery has limits. The early-surgery studies reviewed past records rather than randomly assigning treatment, so the evidence is low-certainty.[1] Wound infection after foot and ankle surgery is also more common with diabetes (9.5% versus 2.4% without it, in one surgeon’s 1,465 operations), and nerve damage was the strongest predictor.[9] Sometimes controlling an infection means removing a toe or part of the foot.[7,4] When that is needed, Dr. Ozturk performs toe, ray and other partial foot amputations, aiming to remove only what’s necessary and keep a foot you can walk on. If an amputation has been recommended and it isn’t urgent, a second opinion can help. Surgery needed to control a spreading infection shouldn’t wait.[1,4]
Recovery and keeping the foot healthy
Clearing the infection comes first; closing the wound often takes much longer. In a study of 299 people with an infected diabetic foot ulcer, 45.5% of the ulcers had healed within a year. Ulcers already open about two months or more healed less often, as did those in feet with reduced blood flow.[5] That is one more reason to have a wound seen early.
Most people who have had a foot infection stay at high risk of new foot problems, so regular foot exams are recommended for life.[1] See keeping your foot in remission, and make a daily foot check (external site) a habit.
When to seek care
See us within a day or two for any foot wound that isn’t healing, especially if you have diabetes. If a wound becomes red, warm, swollen, painful or starts to drain, call us that day at 908-215-5953. If we’re closed, go to urgent care or the emergency department. We treat foot wounds at all three offices: Lyndhurst, Paramus and Millburn.
References
- 1.Senneville É, Albalawi Z, van Asten SA, Abbas ZG, Allison G, Aragón-Sánchez J, et al. IWGDF/IDSA guidelines on the diagnosis and treatment of diabetes-related foot infections (IWGDF/IDSA 2023). Diabetes Metab Res Rev. 2024;40(3):e3687. PubMed 37779323 (external site)
- 2.Lavery LA, Armstrong DG, Murdoch DP, et al. Validation of the Infectious Diseases Society of America's diabetic foot infection classification system. Clin Infect Dis. 2007;44(4):562-5. PubMed 17243061 (external site)
- 3.Tan JS, Friedman NM, Hazelton-Miller C, et al. Can aggressive treatment of diabetic foot infections reduce the need for above-ankle amputation? Clin Infect Dis. 1996;23(2):286-91. PubMed 8842265 (external site)
- 4.Faglia E, Clerici G, Caminiti M, et al. The role of early surgical debridement and revascularization in patients with diabetes and deep foot space abscess: retrospective review of 106 patients with diabetes. J Foot Ankle Surg. 2006;45(4):220-6. PubMed 16818148 (external site)
- 5.Ndosi M, Wright-Hughes A, Brown S, et al. Prognosis of the infected diabetic foot ulcer: a 12-month prospective observational study. Diabet Med. 2018;35(1):78-88. PubMed 29083500 (external site)
- 6.Lavery LA, Armstrong DG, Wunderlich RP, et al. Risk factors for foot infections in individuals with diabetes. Diabetes Care. 2006;29(6):1288-93. PubMed 16732010 (external site)
- 7.National Institute of Diabetes and Digestive and Kidney Diseases. Diabetes and Foot Problems. niddk.nih.gov (external site)
- 8.Chen P, Vilorio NC, Dhatariya K, Jeffcoate W, Lobmann R, McIntosh C, et al. Guidelines on interventions to enhance healing of foot ulcers in people with diabetes (IWGDF 2023 update). Diabetes Metab Res Rev. 2024;40(3):e3644. PubMed 37232034 (external site)
- 9.Wukich DK, McMillen RL, Lowery NJ, Frykberg RG. Surgical site infections after foot and ankle surgery: a comparison of patients with and without diabetes. Diabetes Care. 2011;34(10):2211-3. PubMed 21816974 (external site)
This page is general health information and isn’t a substitute for advice from a clinician who knows your history. Read our medical disclaimer and how we review content.
Related topics
Treatment
Diabetic foot infection surgery
An operation that drains pus and removes dead and infected tissue from a diabetic foot infection, often in stages, before the wound is closed.
Condition
Osteomyelitis (bone infection)
An infection of the bone in the foot, usually spreading from a diabetic foot ulcer, treated with culture-based antibiotics and often surgery to remove the infected bone.
Symptom guide
Red, hot, swollen foot
How infection, active Charcot, gout and a blood clot differ when a foot with diabetes turns red, hot and swollen, and why it needs a call the same day.
Condition
Necrotizing infections
A rare, fast-spreading infection beneath the skin of the foot or leg that needs emergency surgery.
Condition
Diabetic foot ulcers
Open sores on the feet of people with diabetes, and the step-by-step care, including surgery when it’s needed, that aims to heal them and keep them closed.