A red, hot, swollen foot with diabetes: infection, Charcot or gout?

If you have diabetes and one foot turns red, hot and swollen, call us the same day; you don’t need to work out the cause first. If the redness is spreading fast, or you have a fever, chills, confusion or feel unwell, call 911 or go to the emergency department instead. If our office is closed, don’t wait for the next business day: go to urgent care or the emergency department.

Why a red, swollen foot is different with diabetes

With diabetes-related nerve damage (neuropathy), a hot, swollen foot may hurt only a little or not at all, which makes it easy to keep walking on a foot that needs rest.⁠^[2] The Lower Extremity Nerve Institute explains peripheral neuropathy (external site).

Fever, chills and a very high white blood cell count are uncommon in diabetic foot infections; when they appear, they signal a serious one. About half of people diagnosed with a diabetic foot infection have a normal white count.⁠^[1]

Before calling a red foot infected, the infection guideline asks doctors to rule out injury, gout, active Charcot, a fracture, a blood clot and poor vein circulation (venous stasis).⁠^[1]

The usual causes and how they differ

The table shows typical patterns. Real feet don’t always follow them, and Charcot can occur alongside an ulcer or an infection.⁠^{[1,2,3,5,6,7]}

Infection. In a diabetic foot, infection most often follows a break in the skin, usually an ulcer, and almost all bone infections start from an infected ulcer.⁠^[1,3] Redness alone can mislead: at one large hospital, 79 of 259 people (30.5%) admitted with leg cellulitis turned out to have another condition.⁠^[8] Read more about diabetic foot infections.

Active Charcot foot. Charcot usually affects the midfoot, while bone infection more often involves the toes and forefoot. Feeling is badly reduced, but the foot pulses are usually normal or even stronger than normal.⁠^[3] A temperature difference of 2 °C (about 4 °F) between matching spots on the two feet has been used as a threshold in several studies, but warmth alone neither proves nor rules out Charcot.⁠^[2] See Charcot foot.

Gout. Gout tends to come on fast in a single foot or ankle joint, especially the big toe joint, and earlier attacks like it support the diagnosis. Urate crystals in fluid drawn from the joint confirm it; a high uric acid level alone does not.⁠^[5] Having had gout before doesn’t rule out infection or Charcot, so a new hot, swollen foot still needs a same-day check.

A blood clot. A deep vein clot (DVT) mainly affects the lower leg and thigh, most often on one side. It is often checked with a Doppler ultrasound of the leg and a D-dimer blood test, and treated with blood-thinning medicine.⁠^[6] A suspected clot needs that ultrasound the same day; if it can’t be arranged promptly, go to the emergency department.

Poor circulation. Severe artery disease can redden a foot too: in its most serious form, the foot usually turns red when it hangs down and pale when it is raised. It often feels cool, and forefoot pain tends to worsen lying down and ease when the leg hangs over the bed.⁠^[7] That also needs a same-day call; see foot pain at night and dark or discolored toes.

What to tell us when you call

A few observations help us decide how quickly to see you:

• Is there a wound? Check between the toes and around any callus. No current or recent wound makes infection much less likely.⁠^[3]
• Is it warmer than the other foot? Feel both feet with the same hand. Doctors also compare warmth by touch when no skin thermometer is available.⁠^[2]
• Do you feel unwell? Fever, chills or confusion can mean a serious infection: go to the emergency department or call 911 rather than waiting for an appointment.⁠^[1]

Keep weight off the foot until you are seen. A daily foot check (external site) catches changes early.

How we tell them apart

Dr. Ozturk examines both feet side by side, comparing warmth, swelling, feeling and pulses, and looking for any break in the skin. Redness that fades when the leg is raised points away from infection.⁠^[3] If the foot goes pale when raised, poor circulation is more likely.⁠^[7]

The Charcot guideline calls for X-rays, ideally of both feet and taken standing, plus an MRI if they look normal but Charcot is still suspected. It suggests not relying on blood tests to confirm or rule it out.⁠^[2] We take X-rays and ultrasound and do noninvasive circulation testing at our practice, and arrange MRI at an outside imaging center.

Blood tests help when infection is uncertain, and a very high sedimentation rate (above 70 mm per hour) with no other explanation favors bone infection over Charcot.⁠^[1,3] Because Charcot can make X-rays and MRI look like infection, a bone sample is sometimes needed to settle the question.⁠^[1] Dr. Ozturk performs bone biopsy when needed. See how a foot wound is evaluated and bone infection.

Why the same day matters

For Charcot, the guideline recommends knee-high immobilization promptly, while tests are under way. Left untreated, active Charcot carries a high risk of fractures, dislocations, deformity, ulcers, infection and even amputation.⁠^[2] In a study of 22 feet with early Charcot not yet visible on X-ray, the feet that progressed had waited 8.7 weeks on average for treatment, versus 4.1 weeks for those that didn’t. Half the feet needed surgery, though none needed an amputation during follow-up.⁠^[4] When Charcot is likely, we place a total contact cast or another knee-high device that can’t be removed, and show you how to get around safely.

For infection, diabetic foot infections tend to progress, sometimes quickly. A severe infection, one that affects the whole body with fever, chills or feeling unwell, needs emergency care the same day. The guideline advises considering a hospital stay for it, says an experienced specialist should evaluate it within 24 hours, and notes that trapped pus usually needs draining within 24 hours.⁠^[1]

For emergencies, call 911 or go to the emergency department if redness is spreading quickly or you have blisters, dark or discolored skin, a crackling feeling under the skin or new numbness over the area. These signal a more serious infection.⁠^[1] See necrotizing infections.

When surgery is the step that saves the foot

For moderate and severe foot infections, the guideline suggests considering surgery within 24–48 hours, alongside antibiotics, to remove infected and dead tissue.⁠^[1] Dr. Efe Ozturk, a Foot and Ankle Surgeon who is board certified in wound care (FAPWH), drains infection, removes dead tissue and infected bone, and chooses antibiotics from culture results. See surgery for diabetic foot infection.

For Charcot, the guideline suggests considering surgery for unstable joints, a deformity likely to cause an ulcer inside the offloading device, or pain that a cast or knee-high device can’t control. Reconstruction can realign and fuse joints, adjust tendons or remove a prominent bone so the foot rests flat and spreads pressure more evenly.⁠^[2] Dr. Ozturk performs Charcot reconstruction for the feet that need it.

Surgery has limits. Charcot surgery has high complication rates, including wound infection and breakdown, bones that don’t fuse and failed hardware, so the guideline recommends a period of immobilization first to let the inflammation settle.⁠^[2] Infection after surgery is also more common with diabetes: in one surgeon’s series of 1,465 consecutive foot and ankle operations of all kinds, 9.5% of the operations in people with diabetes were followed by a surgical site infection, versus 2.4% in people without. Nerve damage, Charcot and smoking were each linked to a higher risk.⁠^[9] We plan around these risks with you.

When to seek care

If you have diabetes or numb feet and one foot becomes red, warm or swollen, call us the same day at 908-215-5953, even if it doesn’t hurt. The same applies to new foot pain at rest if you have poor circulation. Outside office hours (Monday to Friday, 9 to 5; Saturday by appointment), go to urgent care or the emergency department rather than waiting. See us within a day or two for any foot wound that isn’t healing, especially if you have diabetes.