Diabetes can damage nearly every organ system in the body, from the eyes and kidneys to the heart, nerves, skin, and brain. These complications develop because chronically elevated blood sugar injures blood vessels and nerves over time. Some consequences, like heart disease, are life-threatening. Others, like skin infections or gum disease, are less dramatic but still affect quality of life. Here’s a thorough look at the full range of complications that can result from diabetes.
How High Blood Sugar Damages the Body
The root cause of most diabetes complications is prolonged exposure to high blood sugar. Excess glucose in the bloodstream triggers several chemical chain reactions that produce harmful byproducts called advanced glycation end-products, or AGEs. These molecules damage the walls of blood vessels and activate inflammatory signals in cells throughout the body. At the same time, high blood sugar increases oxidative stress, essentially overwhelming the body’s ability to neutralize damaging free radicals. This combination of inflammation and oxidative damage affects both small blood vessels (leading to eye, kidney, and nerve problems) and large blood vessels (leading to heart attacks, strokes, and poor circulation in the legs).
Heart Disease, Stroke, and Poor Circulation
Cardiovascular disease is the leading cause of death among people with diabetes. Men with diabetes have roughly 2.3 times the risk of having a heart attack compared to men without diabetes. The risk of ischemic stroke is similarly elevated at about 2.3 times, while hemorrhagic stroke risk is about 1.6 times higher. If a person with diabetes needs heart bypass surgery, their operative mortality risk is 67% higher than for someone without diabetes.
Peripheral artery disease (PAD), where narrowed arteries reduce blood flow to the legs and feet, is also far more common. Among adults 65 and older, people with diabetes have twice the rate of PAD and 2.5 times the risk of developing cramping leg pain during walking. Poor circulation in the legs compounds other complications, particularly foot ulcers and infections, because damaged tissue doesn’t receive enough blood to heal properly.
Nerve Damage and Its Many Forms
Diabetic neuropathy is the most common microvascular complication, affecting roughly 13% of people with type 2 diabetes. It comes in several distinct forms, each affecting different parts of the nervous system.
Peripheral neuropathy typically starts in the feet and legs, sometimes spreading to the hands and arms. You might feel numbness, tingling, burning, or shooting pain. The loss of sensation is particularly dangerous because you may not notice a cut, blister, or sore on your foot until it becomes seriously infected. Nerve damage can also impair balance and coordination, raising the risk of falls and fractures.
Autonomic neuropathy damages the nerves controlling internal organs. This can disrupt heart rate and blood pressure regulation, slow digestion, cause bladder problems, interfere with sexual function, and impair the ability to sense when blood sugar drops dangerously low.
Proximal neuropathy is rarer but disabling. It causes severe pain in the hip, buttock, or thigh, usually on one side of the body, and can lead to significant weight loss. Focal neuropathy involves damage to a single nerve, most commonly in the wrist (carpal tunnel syndrome), hand, head, or torso.
Kidney Disease
Diabetic kidney disease develops when high blood sugar damages the tiny filtering units inside the kidneys. About 12% of people with type 2 diabetes develop it. The earliest sign is small amounts of protein leaking into the urine, a stage called microalbuminuria. At this point, kidney filtration rate typically remains stable, and the damage may be slowed or partially reversed with good blood sugar and blood pressure control.
If the disease progresses to macroalbuminuria, where larger amounts of protein spill into the urine, kidney function begins a steady decline. Without intervention, kidney filtration can drop by roughly 0.5 to 1.2 milliliters per minute each month, depending on diabetes type. Eventually this can lead to end-stage kidney disease requiring dialysis or a transplant. Screening involves a simple yearly urine test starting at diagnosis for type 2 diabetes, or five years after diagnosis for type 1.
Eye Disease and Vision Loss
Diabetic retinopathy occurs when high blood sugar damages the small blood vessels in the retina. These vessels can swell, leak fluid, or close off entirely. In advanced stages, fragile new blood vessels grow on the retina’s surface and can bleed into the eye, potentially causing vision loss or blindness. Retinopathy affects roughly 6% of people with type 2 diabetes in studies, though rates increase significantly with longer disease duration.
Because retinopathy often causes no symptoms in its early stages, screening is essential. People with type 2 diabetes should have a dilated eye exam at diagnosis, then every one to two years. Those with type 1 diabetes should start screening within five years of diagnosis. If signs of eye disease are found, exams become at least annual.
Foot Ulcers and Amputation
Diabetic foot complications are among the most devastating consequences of the disease. Approximately 18.6 million people worldwide develop a diabetic foot ulcer each year, including 1.6 million in the United States. These ulcers typically start as minor wounds that go unnoticed due to nerve damage, then worsen because poor circulation slows healing.
Foot ulcers precede 80% of lower-limb amputations in people with diabetes. About 20% of moderate to severe foot infections lead to amputation. Daily foot inspection, proper footwear, and routine care are the most effective ways to catch problems early and prevent this progression.
Digestive Problems and Gastroparesis
When autonomic nerve damage reaches the stomach, it can cause gastroparesis, a condition where the stomach empties food far too slowly. The main symptoms are nausea, vomiting, feeling full after just a few bites, bloating, and upper abdominal pain. These symptoms can make it extremely difficult to manage blood sugar, because food absorption becomes unpredictable. Gastroparesis is diagnosed when a standardized meal test shows that more than 10% of food remains in the stomach after four hours.
Skin Conditions
Diabetes increases susceptibility to a wide range of skin problems. Some are common conditions that simply occur more frequently in people with diabetes: bacterial infections like boils, styes, and carbuncles; fungal infections such as athlete’s foot, jock itch, and yeast infections; and persistent itching, especially on the lower legs when circulation is poor.
Other skin conditions are more specific to diabetes. Diabetic dermopathy causes light brown, scaly patches on the shins. Necrobiosis lipoidica produces larger, deeper skin lesions that can become shiny and thin. Diabetic blisters can appear on the fingers, hands, toes, or feet. Digital sclerosis causes thick, tight, waxy skin on the backs of the hands and sometimes the toes or forehead, restricting joint movement.
Gum Disease and Cognitive Decline
Diabetes significantly raises the risk of periodontitis, a serious form of gum disease that destroys the tissue and bone supporting the teeth. The relationship runs both ways: gum disease also makes blood sugar harder to control, creating a cycle that worsens both conditions.
Research now links diabetes and gum disease to cognitive decline as well. Both conditions fuel chronic, body-wide inflammation that may contribute to neurodegeneration. In studies of diabetic patients, those with more severe gum disease had dramatically higher odds of being at risk for mild cognitive impairment. Diabetes on its own is an established risk factor for dementia, and untreated gum disease appears to compound that risk. Managing oral health is one practical step that may help protect brain function over time.
Screening Timelines That Matter
Many diabetes complications develop silently, so regular screening catches damage before symptoms appear. For type 2 diabetes, eye exams and kidney urine tests should begin at the time of diagnosis. For type 1, both screenings start five years after diagnosis, then repeat annually. Ankle blood pressure testing for peripheral artery disease is recommended if you develop symptoms like leg cramping during walking. Foot exams should happen at every routine diabetes visit, and daily self-checks at home are one of the simplest ways to prevent the most serious complications.