Acute Complication: Diabetic Ketoacidosis (DKA)

Occurs when the body has a critical shortage of insulin and starts breaking down fat for energy, producing acidic ketone bodies that build up in the blood. It's most common in type 1 diabetes, though it can also occur in type 2. Triggers can include infection, a missed or incorrect insulin dose, stroke, or taking steroids. Symptoms: nausea, vomiting, abdominal pain, deep labored breathing, a fruity breath odor, and in severe cases, confusion or coma. The frequency of this complication varies significantly between countries; with modern treatment, mortality is estimated at less than 1–5%.

Hyperosmolar Hyperglycemic State

Severe hyperglycemia with pronounced dehydration, usually without significant ketoacidosis. Unlike DKA, it develops gradually — over days or weeks. It's most often linked to type 2 diabetes. Symptoms: marked thirst, urination, weakness, and later confusion, vision changes, and low blood pressure. Mortality for this condition is estimated to be higher than for typical DKA — roughly around 15%.

Hypoglycemia (Excessively Low Blood Sugar)

Usually defined as a glucose level below 3.9 mmol/L (70 mg/dL); the conventional normal range is considered to be roughly 3.9–6.1 mmol/L. Noticeable symptoms often appear only with a further drop, around 3.0 mmol/L (55 mg/dL) or below. Symptoms fall into two groups: "autonomic" (rapid heartbeat, sweating, tremor, anxiety, hunger) and "neuroglycopenic" (confusion, blurred vision, slurred speech, seizures, loss of consciousness). In people with diabetes, the cause is usually insulin or certain glucose-lowering medications, especially when the dose isn't matched to food intake, a meal is skipped, there's been excessive physical activity, or alcohol has been consumed.

Chronic Complication: Diabetic Retinopathy (Eyes)

Damage to the blood vessels of the retina from prolonged hyperglycemia — one of the leading causes of vision loss among the working-age population (20–64 years) in developed countries. In its early stages it's usually asymptomatic. Some degree of retinopathy is estimated to develop in about 35% of people with diabetes; among people with type 1 diabetes, in roughly 25% within 5 years of diagnosis and up to 80% within 15 years. Modern treatment can prevent severe vision loss in about 90% of cases.

Chronic Complication: Diabetic Nephropathy (Kidneys)

A chronic decline in kidney function — one of the leading causes of chronic kidney disease and end-stage renal failure worldwide. It usually progresses gradually over years: from a small amount of protein in the urine (microalbuminuria) to pronounced proteinuria and, eventually, the need for dialysis or transplantation. Early stages are typically asymptomatic; later symptoms (often after 5–10 years) include swelling, fatigue, headache, nausea, and itchy skin. Estimates suggest kidney complications develop in about 25–33% of people with diabetes.

Chronic Complication: Diabetic Neuropathy (Nerves)

Nerve damage linked to injury of the small blood vessels that supply them. The most common form is peripheral (sensorimotor) polyneuropathy, which primarily affects the longer nerves (feet, legs), causing numbness, tingling, and burning pain. Autonomic neuropathy can affect the heart, digestion, bladder, and sexual function. Peripheral neuropathy is estimated to affect about 30% of people with diabetes (roughly 132 million people globally). Loss of sensation makes foot injuries and ulcers go unnoticed, and this complication is estimated to be involved in 50–75% of non-traumatic lower-limb amputations.

Cardiovascular Disease and Other Effects

Diabetes roughly doubles the overall risk of cardiovascular disease; about 75% of deaths among people with diabetes are linked to coronary heart disease. Diabetes is also associated with an increased risk of stroke and peripheral artery disease (which further impairs circulation and raises amputation risk). Other associated conditions mentioned in the medical literature include hearing loss, gallstone disease, cognitive decline and dementia, cataracts, and glaucoma.

This article describes complications in a general, informational format. Only a doctor can assess individual risk and order complication screening.