Diabetes can cause damage to nearly every organ system in the body, from the heart and kidneys to the eyes, nerves, skin, and even mental health. The common thread is prolonged high blood sugar, which injures blood vessels and nerves over time. Some complications develop slowly over years, while others can strike as medical emergencies. Here’s what diabetes can do to your body and what to watch for.
Heart Disease and Stroke
Heart disease is the leading cause of death among people with diabetes. According to the CDC, people with diabetes have twice the risk of heart disease compared to those without it. High blood sugar damages the walls of arteries over time, making them stiffer and more prone to plaque buildup. This narrows the vessels that supply blood to the heart and brain, raising the odds of a heart attack or stroke.
The risk compounds when diabetes occurs alongside high blood pressure, high cholesterol, or smoking. But even when those factors are well controlled, diabetes itself remains an independent driver of cardiovascular damage.
Eye Damage and Vision Loss
Diabetes is one of the leading causes of preventable blindness. The condition it causes, diabetic retinopathy, happens when high blood sugar damages the tiny blood vessels in the retina. In its early stages, small bulges form in these vessels and may leak fluid. As it progresses, the damage becomes more widespread, and in the most advanced stage, new abnormal blood vessels grow across the retina, which can bleed and cause sudden vision loss.
The longer someone has diabetes, the more likely retinopathy becomes. After 10 to 15 years with type 1 diabetes, 25 to 50 percent of people show some signs of retinopathy. That number climbs to 75 to 95 percent after 15 years and approaches 100 percent after 30 years. Type 2 diabetes follows a similar pattern, though some people already have early retinopathy at the time of diagnosis because the disease often goes undetected for years. The damage is usually painless and invisible to you until it’s advanced, which is why annual eye exams matter.
Kidney Disease
Your kidneys filter waste from the blood through millions of tiny blood vessels. Diabetes damages those vessels, gradually reducing the kidneys’ ability to do their job. The earliest sign is small amounts of protein leaking into the urine, something you wouldn’t notice on your own but that shows up on routine lab tests.
Kidney disease from diabetes progresses through stages based on how well the kidneys are filtering. In early stages, function is still near normal and the damage is reversible with good blood sugar and blood pressure control. In later stages, filtering drops significantly, and the kidneys may eventually fail entirely, requiring dialysis or a transplant. Diabetes is the single most common cause of kidney failure in the United States.
Nerve Damage
Diabetic neuropathy affects up to half of all people with diabetes and comes in several forms. The most common is peripheral neuropathy, which targets the feet and legs first, then sometimes the hands and arms. It typically starts as tingling, numbness, or a burning sensation. Over time, you may lose the ability to feel temperature changes or pain in your feet, which creates a dangerous situation: injuries go unnoticed and infections can take hold.
A less well-known form is autonomic neuropathy, which damages the nerves that control involuntary body functions. This can cause slow stomach emptying (leading to nausea, vomiting, and feeling full after small meals), bladder problems, a resting heart rate that’s abnormally fast, dizziness when standing up, and excessive or reduced sweating. One particularly risky effect is losing the ability to feel when blood sugar drops dangerously low, because the usual warning signs like shakiness and sweating depend on nerves that may no longer function properly.
There’s also proximal neuropathy, which causes severe pain in the thighs, hips, or buttocks, and focal neuropathy, which strikes a single nerve suddenly, sometimes causing double vision or pain in a specific area.
Foot Problems and Amputation
Diabetes creates a perfect storm for foot complications. Nerve damage means you may not feel a blister, cut, or pressure sore. Poor circulation means wounds heal slowly. And a weakened immune response means infections take hold more easily. Diabetic foot ulcers develop in an estimated 10 to 25 percent of people with diabetes during their lifetime.
When ulcers become infected or blood flow is too poor for healing, amputation can become necessary. Between 40 and 85 percent of all non-traumatic lower limb amputations involve people with diabetes. The risk is highest in older adults, people with kidney disease or heart disease, and those with severely reduced blood flow to the legs. Daily foot inspections, properly fitting shoes, and prompt attention to any wound are the most effective prevention strategies.
Skin Conditions
Skin problems are among the earliest visible signs of diabetes, and some appear even before a diagnosis. Acanthosis nigricans causes dark, velvety patches in body creases like the neck, armpits, and groin, and is closely linked to insulin resistance. Diabetic dermopathy, also called shin spots, produces harmless red or brown round patches on the shins. Digital sclerosis makes the skin on the fingers thick and waxy, eventually limiting joint movement.
Other skin manifestations include diabetic blisters on the lower legs and feet that look alarming but are painless and heal on their own, and eruptive xanthomatosis, small reddish-yellow bumps that can appear on the hands, feet, and limbs. People with diabetes are also more prone to bacterial infections (especially around hair follicles and fingernails) and fungal infections like athlete’s foot and yeast infections, because high blood sugar creates a favorable environment for microbes to thrive.
Gum Disease and Tooth Loss
Diabetes significantly raises the risk of periodontitis, a severe form of gum disease that can lead to tooth loss. High blood sugar triggers excessive production of damaging molecules called free radicals in the gum tissue, which overwhelms the body’s natural defenses and fuels chronic inflammation. This inflammation breaks down the bone that holds teeth in place.
Diabetes also shifts the balance of bacteria living beneath the gumline, reducing the diversity of the oral microbiome and promoting the growth of specific disease-causing species. The relationship runs both directions: severe gum disease can make blood sugar harder to control, creating a cycle that worsens both conditions.
Acute Emergencies
Beyond the slow-building complications, diabetes can cause two life-threatening emergencies that require immediate medical attention.
Diabetic ketoacidosis happens most often in type 1 diabetes when the body has almost no insulin and starts breaking down fat for fuel at a dangerous rate. This floods the blood with acids called ketones. Blood sugar usually rises above 250 mg/dL, and the blood becomes dangerously acidic. Symptoms include extreme thirst, frequent urination, nausea, abdominal pain, fruity-smelling breath, and confusion. Without treatment, it can be fatal within hours.
Hyperosmolar hyperglycemic state is more common in type 2 diabetes and develops when blood sugar climbs to extreme levels, often above 800 mg/dL. The body becomes severely dehydrated, but ketone production is typically minimal. Symptoms come on gradually over days or weeks, starting with increased thirst and urination and progressing to confusion, seizures, or coma. It carries a higher mortality rate than ketoacidosis, partly because it tends to affect older adults and is often recognized late.
Mental Health Effects
The toll of diabetes isn’t purely physical. More than half of U.S. adults with diabetes experience some level of diabetes distress, a specific type of emotional burden tied to managing the condition. About 24 percent report moderate distress, and 7 percent experience severe distress that interferes with their ability to manage their health. This isn’t the same as clinical depression, though the two overlap. Diabetes distress comes from the relentless daily demands of the disease: monitoring blood sugar, managing medications, worrying about complications, and navigating dietary restrictions.
Over an 18-month period, the cumulative incidence of significant diabetes distress ranges from 38 to 48 percent, meaning it’s not a one-time experience but something that comes and goes. People who are younger, have lower incomes, or use insulin are at higher risk. Left unaddressed, distress leads to poorer blood sugar control, which in turn accelerates the physical complications described above.