Diabetes affects nearly every system in the body. Over time, elevated blood sugar damages blood vessels and nerves, leading to complications that range from heart disease and kidney failure to vision loss, chronic pain, and mental health struggles. At age 50, people with type 2 diabetes have a life expectancy roughly 6 years shorter than people without the condition. But the severity of these effects depends heavily on how well blood sugar is managed, and many complications are preventable or can be slowed significantly.
Heart Disease and Blood Vessel Damage
Cardiovascular disease is the leading cause of death among people with diabetes. The risk of heart disease is twice as high in people with diabetes compared to those without it. High blood sugar gradually damages the lining of blood vessels, making them stiffer and more prone to plaque buildup. This accelerates atherosclerosis, the narrowing of arteries that leads to heart attacks and strokes.
The damage isn’t limited to the heart. Blood vessel disease throughout the body contributes to poor circulation in the legs and feet, slower wound healing, and higher blood pressure. These vascular changes are the root cause behind many of the other complications on this list, from kidney disease to vision problems.
Nerve Damage and Chronic Pain
Diabetic neuropathy is one of the most common and disruptive effects of diabetes. It comes in several forms, and the symptoms depend on which nerves are affected.
Peripheral Neuropathy
This is the most common type. It typically starts in the feet and toes, then can progress to the legs, hands, and arms, usually affecting both sides of the body at once. Early symptoms include numbness, tingling, or a reduced ability to feel pain and temperature changes. As it worsens, people may experience sharp, jabbing pain that intensifies at night, burning sensations, or extreme sensitivity to touch. Some people find even the weight of a bedsheet painful. Over time, muscle weakness and loss of reflexes can develop, and the inability to feel injuries in the feet sets the stage for serious infections.
Autonomic Neuropathy
Diabetes can also damage the nerves that control internal organs. This affects blood pressure regulation, heart rate, digestion, bladder function, and sexual health. One well-known consequence is gastroparesis, where the stomach empties too slowly, causing nausea, vomiting, bloating, and loss of appetite. Sexual dysfunction is also common: difficulty getting or maintaining an erection in men, and vaginal dryness, reduced sensation, or difficulty with arousal and orgasm in women.
Mononeuropathy
Less commonly, diabetes damages a single nerve in the face, torso, arm, or leg. This tends to come on suddenly and can cause focused pain or weakness in one area. Sometimes multiple individual nerves in different parts of the body are affected at the same time.
Kidney Disease
The kidneys filter waste from your blood through millions of tiny blood vessels, and high blood sugar damages those vessels over years. About 38% of adults with diabetes have some degree of chronic kidney disease. The numbers are even higher for type 1 diabetes, where roughly half of adults are affected.
Early kidney damage produces no symptoms. By the time you notice swelling in your ankles, fatigue, or changes in urination, the disease has often progressed significantly. Left unchecked, diabetic kidney disease can lead to kidney failure requiring dialysis or a transplant. Regular screening through simple blood and urine tests is the main way to catch it early, when treatment can slow the decline.
Foot Problems and Amputation Risk
Diabetes is the leading risk factor for lower-limb amputation in U.S. adults, with an estimated 150,000 diabetes-related amputations performed each year. The pathway to amputation usually starts with something small: a blister, cut, or pressure sore on the foot that goes unnoticed because nerve damage has dulled sensation. Poor circulation then slows healing, and infection can set in quickly.
These wounds, called diabetic foot ulcers, develop in up to 8% of people with diabetes in any given year in community settings. About 20% of people who develop a foot ulcer will eventually need some form of amputation, either below or above the ankle. Daily foot checks, properly fitting shoes, and prompt treatment of any wound are the most effective ways to prevent this progression.
Blood Sugar Emergencies
Diabetes can also cause acute, life-threatening crises when blood sugar spins out of control.
Diabetic ketoacidosis (DKA) happens primarily in type 1 diabetes, though it can occur in type 2 as well. When the body can’t produce enough insulin, it starts breaking down fat for energy at a dangerous rate, producing acidic compounds called ketones. Blood sugar rises above 250 mg/dL, the blood becomes acidic, and without treatment, it can lead to coma or death. Warning signs include excessive thirst, frequent urination, nausea, abdominal pain, and fruity-smelling breath.
Hyperosmolar hyperglycemic state (HHS) is more common in type 2 diabetes. Blood sugar climbs above 600 mg/dL, causing severe dehydration and confusion. Unlike DKA, it involves little or no ketone production, but the extreme dehydration and blood sugar levels can cause seizures, coma, and death. HHS develops more slowly than DKA, often over days or weeks, which means it’s sometimes caught late. About one-third of patients with these emergencies show features of both conditions.
Oral Health
High blood sugar weakens white blood cells, your body’s primary defense against infection. In the mouth, this creates an environment where harmful bacteria thrive, increasing the risk of cavities and gum disease. Gum disease in people with diabetes tends to be more severe and slower to heal. The relationship also works in reverse: active gum disease makes blood sugar harder to control, creating a cycle that worsens both conditions.
Mental Health and Emotional Burden
Living with diabetes takes a real psychological toll that often goes unrecognized. More than half of U.S. adults with diabetes experience some level of diabetes distress, a form of emotional strain tied specifically to managing the condition. About 24% experience moderate distress, and 7% report severe distress. Over an 18-month period, the cumulative rate of significant distress ranges from 38% to 48%, meaning it affects most people with diabetes at some point.
Diabetes distress is distinct from clinical depression, though the two overlap. It includes feelings of being overwhelmed by self-management demands, worry about complications, frustration with blood sugar fluctuations, and guilt or shame around eating. These feelings can lead to burnout, where people stop checking blood sugar or taking medications consistently, which then accelerates physical complications.
How These Effects Connect
Most complications of diabetes share a common root: prolonged exposure to high blood sugar damages blood vessels and nerves throughout the body. This means the effects rarely happen in isolation. Someone with nerve damage in their feet is also likely developing changes in their kidneys and blood vessels. The earlier and more consistently blood sugar is managed, the more these cascading effects can be delayed or reduced. Even modest improvements in blood sugar control meaningfully lower the risk of complications across every organ system.