Complications of Diabetes

January 7, 2025

This page was reviewed under our medical and editorial policy by Ping H. Wang, M.D., professor and chair, Department of Diabetes, Endocrinology & Metabolism, City of Hope^® Cancer Center Duarte

Diabetes occurs when blood sugar levels are too high. Diabetes and associated metabolic disorders slowly damage blood vessels, nerves, eyes, kidneys and other organs throughout the body, which may lead to a variety of complications. The body uses a hormone called insulin to help move glucose from the blood into cells for energy. In type 1 diabetes, the body does not produce insulin, while in type 2 diabetes, it does not use insulin appropriately.

Whether a patient experiences complications and which ones depends on the type of diabetes and how well the condition is managed.

Heart and Cardiovascular Problems

Heart and vascular problems are common complications of diabetes, affecting people with both type 1 and type 2 diabetes. Over time, diabetes may damage the blood vessels and heart muscles, leading to the development of heart disease and stroke.

People with diabetes are more likely to experience heart-related issues at a younger age than those without the condition. Adults with diabetes are almost twice as likely to have heart disease or suffer a stroke compared to those without diabetes. There are several reasons behind this, as listed below.

High blood pressure: This is common in people with diabetes. High blood pressure forces the heart to work harder to pump blood and increases the risk of heart attack or stroke.

Unhealthy cholesterol levels: LDL, or bad cholesterol, may lead to blockages of the blood vessels, while higher levels of HDL, or good cholesterol, help protect the heart.

Smoking: Tobacco use raises the risk of heart disease even further, especially for people with diabetes. This is because the combination of smoking and high blood sugar accelerates the development of vascular diseases.

Managing blood sugar levels, controlling blood pressure, keeping cholesterol in check and quitting smoking are important steps in lowering the risk of heart and cardiovascular problems in people with diabetes.

Chronic Kidney Disease

Chronic kidney disease (CKD) is another common complication of diabetes, affecting about 1 in 3 adults with the condition, according to the U.S. Centers for Disease Control and Prevention. Patients may also hear it called diabetic nephropathy.

Patients with type 1 or type 2 diabetes may experience CKD, which develops slowly and often without noticeable symptoms in the early stages. Many people do not realize they have kidney damage until it is advanced and requires serious treatment like dialysis, a process that filters the blood.

CKD happens because diabetes damages the blood vessels and tissues in the kidneys over time. The kidneys contain millions of tiny filters called nephrons, which help remove waste from the blood. In diabetes patients, these filters could become damaged over time. This makes it harder for the kidneys to do their job. High blood pressure, which is common in people with diabetes, also adds strain on the kidneys and worsens damage.

Since CKD does not usually cause symptoms in the early stages, regular blood and urine tests are important for people with diabetes. These tests may help detect kidney problems early, when treatment is most successful. Managing blood sugar and blood pressure also helps reduce the risk of developing serious kidney disease.

Diabetic Retinopathy

Diabetic retinopathy (DR) is a common complication of type 1 and type 2 diabetes. It affects the blood vessels in the retina, the part of the eye that helps a person see. High blood sugar levels may damage these blood vessels over time and lead to vision problems. DR is one of the leading causes of vision loss in adults, especially those with long-term or poorly managed diabetes.

In the early stages, diabetic retinopathy may not cause any noticeable symptoms. As the condition worsens, people may experience blurred or distorted vision, spots in their vision, or even partial or complete vision loss. Without proper treatment, DR may lead to blindness.

The risk of developing diabetic retinopathy increases with the length of time a person has diabetes and if blood sugar levels are not well controlled. Treatment is most successful when DR is caught early. Managing blood sugar and regular eye exams may help detect and slow the progression of retinopathy and help prevent serious vision loss.

Other Diabetic Eye Problems

In addition to diabetic retinopathy, people with diabetes may develop other eye problems.

Diabetic macular edema (DME) happens when damaged blood vessels leak fluid into the part of the retina responsible for sharp central vision.

Glaucoma is a group of diseases that damage the optic nerve. In diabetic glaucoma, new blood vessels grow near the iris (the colored part of the eye), blocking fluid drainage. This raises pressure inside the eye.

Cataracts, which cause the eye’s lens to become cloudy, also develop more quickly in people with diabetes.

Diabetic Neuropathy

Diabetic neuropathy affects more than half of people with diabetes (both type 1 and type 2), according to the U.S. National Library of Medicine. Over time, diabetes may damage the protective covering of nerves and the blood vessels that supply them with oxygen. This damage interferes with the way nerves send signals, causing them to misfire, slow down or stop working altogether.

The symptoms of diabetic neuropathy vary depending on which nerves are affected. Many people experience numbness, tingling or burning sensations in their hands, legs or feet. Others may develop digestive problems like nausea, vomiting or diarrhea, as well as issues with sexual function or bladder control. Dizziness when standing up quickly is also a possible symptom.

Diabetic neuropathy may significantly impact quality of life and make everyday activities more difficult. While there is no cure, managing blood sugar levels may help prevent the condition or slow its progression. Treatments are available to help manage pain and other symptoms.

Diabetic Foot Problems

Diabetic foot problems may happen with any type of diabetes and may be serious if not managed properly. Over time, high blood sugar may cause nerve damage, leading to a loss of sensation in the feet. This makes it hard to feel pain, cuts or blisters, which might lead to untreated wounds.

Diabetes may also reduce blood flow to the feet, so if these wounds become infected, they may be slow to heal. In some cases, infections may become so severe that they lead to gangrene, a condition in which the tissue dies.

In extreme cases, gangrene or foot ulcers that do not heal might require amputation (surgically removing the foot) to prevent the infection from spreading and to save the person’s life. Diabetic foot problems might also cause changes in the shape of the feet, such as Charcot’s foot, where bones shift and deform.

The good news is that proper foot care may help prevent these issues. People with diabetes should check their feet daily for any signs of injury, wash them regularly and keep their toenails trimmed. Managing blood sugar levels and getting regular foot exams from a doctor are key to avoiding serious foot complications.

Mouth and Skin Conditions

Diabetes may lead to several mouth and skin problems. High blood sugar levels may affect the saliva in the mouth and the skin’s ability to fight off infections.

People with diabetes are more likely to develop gum disease, cavities and dry mouth. Diabetes or its medications may reduce saliva production. Since saliva helps wash away food and bacteria, having less of it makes tooth decay and gum disease more likely.

Skin problems are sometimes the first sign of diabetes. People with diabetes are more prone to common bacterial and fungal infections. Certain skin conditions, such as diabetic dermopathy (dark patches of skin), diabetic blisters and necrobiosis lipoidica diabeticorum (yellow, swollen patches of skin), occur almost exclusively in people with diabetes.

Although many of these mouth and skin issues may be mild, others may lead to more serious complications. Regular dental checkups, good oral hygiene and keeping blood sugar levels under control may help prevent or manage these problems. It is important to discuss any changes in the mouth or skin with a health care provider.

Hearing Loss

Diabetes may cause hearing problems by damaging the small blood vessels and nerves in the inner ear. High blood sugar over time may lead to nerve damage, affecting how sound signals travel from the inner ear to the brain. This makes hearing loss twice as common in people with diabetes, according to the American Diabetes Association. Even those with prediabetes have a higher risk of hearing loss than people with normal blood sugar levels.

Hearing loss usually happens gradually, making it hard to notice at first. Often, friends or family may point it out before the person realizes there is an issue. While diabetic hearing loss is unable to be reversed, managing blood sugar levels may help prevent further damage, and treatments are available. A full hearing evaluation by a primary care doctor or audiologist, a doctor who specializes in hearing, can help patients learn more about hearing aid devices and strategies to manage hearing loss.

Diabetic Gastroparesis

Diabetes may lead to digestive problems, such as gastroparesis. This condition occurs when high blood sugar causes nerve damage that affects the stomach muscles, slowing down or stopping the normal movement of food through the digestive tract. This may cause symptoms like nausea, heartburn and bloating.

Gastroparesis also makes it harder to manage blood sugar because food is absorbed unpredictably, affecting how much insulin is needed. Over time, this may also lead to malnutrition if the body does not properly absorb nutrients from food.

While there is no cure for gastroparesis, managing blood sugar levels might help prevent or delay it. Lifestyle changes, such as eating smaller meals and avoiding foods that are hard to digest, may also ease symptoms and improve digestion.

Complications in Pregnant Women with Diabetes

Women with preexisting diabetes who become pregnant may face the risk of additional complications if their condition is not well managed.

For the baby, high blood sugar levels during pregnancy might increase the risk for developing birth defects, particularly in the heart, brain and spine. It may also lead to the baby being born prematurely, weighing more than normal or having breathing problems or low blood sugar after birth.

For the mother, diabetes during pregnancy increases the risk for developing preeclampsia, a condition characterized by high blood pressure and excess protein in the urine. Preeclampsia may be dangerous if left untreated and may require early delivery to protect the health of both the mother and the baby. Additionally, pregnancy may worsen existing diabetes-related issues, like kidney disease and eye problems, particularly if blood sugar levels are not well controlled. Some patients may need to start taking insulin even though they did not need it before.

Managing blood sugar levels through diet, exercise and medication (if needed) is necessary for a healthy pregnancy. Regular checkups and careful monitoring may help reduce the risks and ensure the health of both mother and baby.

Complications of Gestational Diabetes

Gestational diabetes is when a woman develops diabetes for the first time during pregnancy, typically diagnosed in the second or third trimester of pregnancy. Gestational diabetes may occur during pregnancy due to hormonal changes that make the body less able to use insulin, similar to type 2 diabetes. While it often has no symptoms, some women may experience increased thirst or the need to urinate more often.

High blood sugar levels during pregnancy may lead to:

• A baby that is oversized
• A baby that is born prematurely
• Breathing problems in the baby
• Low blood sugar right after birth

Delivering a large baby may cause injury or complications for the mother and baby, such as increasing the chances of a cesarean section birth or needing to deliver before 40 weeks.

Babies may also be more likely to become overweight and develop type 2 diabetes as they get older.

If a woman has gestational diabetes, she is at a higher risk for having a miscarriage, high blood pressure, a stillborn birth and developing type 2 diabetes after the pregnancy.

Maintaining a healthy weight, eating nutritious foods and staying active may reduce the risk for developing diabetes and its complications for both mother and child during and after pregnancy.