Type 2 Diabetes Long-Term Complications: What to Know

Why does high blood sugar cause complications?

Chronically elevated glucose is toxic to blood vessels and nerve tissue. It damages the inner lining of small blood vessels (microvascular complications) and accelerates the buildup of plaques in larger arteries (macrovascular or cardiovascular complications). The duration of exposure and the average glucose level — reflected in the HbA1c — are the two primary drivers of complication risk 1Ref 1American Diabetes Association Professional Practice Committee (2024).Standards of Care in Diabetes—2024.Complication pathophysiology, HbA1c targets, screening recommendations for retinopathy, nephropathy, neuropathy, and foot disease, and role of blood sugar control in prevention.

This is why early diagnosis, consistent treatment, and regular monitoring matter so much.

Heart disease and stroke (cardiovascular disease)

Cardiovascular disease is the leading cause of death among people with type 2 diabetes. High blood sugar accelerates atherosclerosis — hardening and narrowing of the arteries — increasing the risk of heart attack and stroke. Type 2 diabetes frequently occurs alongside high blood pressure and abnormal cholesterol, which compound the cardiovascular risk further [1, 2].

Managing blood pressure and LDL cholesterol alongside blood sugar is considered as important as glucose control in reducing cardiovascular risk in type 2 diabetes 2Ref 2American Diabetes Association Professional Practice Committee (2024).10. Cardiovascular Disease and Risk Management: Standards of Care in Diabetes-2024.Cardiovascular disease as the leading cause of death in type 2 diabetes, and recommendations for blood pressure, LDL, and medication class selection.

Kidney disease (diabetic nephropathy)

The kidneys filter blood through a network of tiny vessels that are vulnerable to glucose-related damage. Over years, this damage reduces the kidneys' ability to filter waste, eventually leading to chronic kidney disease and, in advanced cases, kidney failure requiring dialysis or transplant.

Diabetic kidney disease is detected early through urine albumin tests (which pick up small amounts of protein leaking through damaged kidney filters) and eGFR blood tests. Controlling blood sugar and blood pressure — particularly with certain medication classes including ACE inhibitors and SGLT2 inhibitors — slows progression [1, 2].

Eye disease (diabetic retinopathy)

Diabetic retinopathy is damage to the blood vessels of the retina at the back of the eye. In early stages it causes no symptoms. As it progresses, it can lead to vision changes, floaters, and, if untreated, blindness — making it one of the leading causes of preventable vision loss in adults 3Ref 3Flaxel CJ, Adelman RA, Bailey ST, Fawzi A, Lim JI, Vemulakonda GA, Ying GS (2020).Diabetic Retinopathy Preferred Practice Pattern.Diabetic retinopathy as a leading cause of preventable vision loss, progression risk, and role of annual eye exams.

Annual dilated eye exams are recommended for people with type 2 diabetes to catch retinopathy early, when laser treatment or injections can preserve vision. Blood sugar control is the most powerful tool for slowing its development and progression 1Ref 1American Diabetes Association Professional Practice Committee (2024).Standards of Care in Diabetes—2024.Complication pathophysiology, HbA1c targets, screening recommendations for retinopathy, nephropathy, neuropathy, and foot disease, and role of blood sugar control in prevention.

Nerve damage (diabetic neuropathy)

Peripheral neuropathy — numbness, tingling, burning, or pain in the feet and hands — is among the most common complications of long-standing type 2 diabetes. It typically starts in the feet and moves upward in a 'stocking and glove' pattern.

Neuropathy also affects autonomic nerves that control internal organs, potentially causing digestive problems (gastroparesis), bladder dysfunction, sexual dysfunction, and abnormal heart rate or blood pressure responses.

Neuropathy cannot be reversed once established, but blood sugar control slows its progression, and medications can manage pain symptoms when present [1, 4].

Foot problems and amputation

Peripheral neuropathy combined with poor circulation creates conditions where a small foot injury — a blister, cut, or pressure sore — can go unnoticed, become infected, and fail to heal. Severe infection in the foot can, in the worst cases, lead to amputation.

This risk is substantially reduced by regular foot examinations, daily self-inspection of the feet, proper footwear, and prompt attention to any wound or sore. Regular clinician foot checks are a standard part of diabetes care.

Can complications be prevented?

Yes, to a large extent. The evidence is strong that keeping HbA1c in or near a target range — individualized for each person but often below 7% for many adults — meaningfully reduces complication risk 1Ref 1American Diabetes Association Professional Practice Committee (2024).Standards of Care in Diabetes—2024.Complication pathophysiology, HbA1c targets, screening recommendations for retinopathy, nephropathy, neuropathy, and foot disease, and role of blood sugar control in prevention. Equally important: controlling blood pressure, managing cholesterol, not smoking, and attending regular screening appointments (eye exam, kidney function, foot exam, and nerve testing).

People who have already developed some complications can still slow progression through better control — it is not too late to benefit from improved management at any stage.