Complications of type 1 diabetes

People with type 1 diabetes have a greater chance of developing a variety of complications and health problems, especially if their blood glucose is not well managed. Whether — and how fast — these complications develop depends on how long a person has had diabetes, and how well their blood pressure, cholesterol and blood glucose levels have been controlled.

It’s not just about glucose

If you have diabetes, managing your blood pressure and cholesterol are just as important as managing your blood glucose levels. This is because research has shown that lowering blood pressure and cholesterol can prevent 3 times as many heart attacks and strokes compared with lowering blood glucose alone.

People who smoke, have high blood pressure and high cholesterol, and have a heavy alcohol intake are more likely to develop complications sooner. Many of the complications of diabetes are related to blood vessel damage as a result of high cholesterol, smoking and high blood pressure. So if you have diabetes, it is important to do whatever you can to prevent these complications by using your diabetes medicine (injected insulin) and making lifestyle changes — it’s never too late to try.

People with diabetes are much more likely than other people to develop the conditions below.

Eye complications

Some eye conditions, such as cataracts (clouding in the lens of the eye affecting vision) and glaucoma, are more common in people with diabetes. Disease of the small blood vessels of the eye can also cause areas of the retina (the light sensitive tissue at the back of the eye) to die, resulting in loss of vision (diabetic retinopathy).

A diagram illustrating how the eye is affected in people with glaucoma

People who have diabetes are at high risk of getting glaucoma. Image:

This diagram illustrates how the eye is affected in people with glaucoma. Abnormally high pressure from the fluid that builds up inside the eye can put pressure on the optic nerve (the nerve that goes from the eye to the brain and enables us to see), damaging it resulting in vision loss.

Damage to the optic nerve can also be caused by poor blood supply to the optic nerve, and/or a problem with the optic nerve or nerve fibres themselves.

Kidney disease

Your kidneys play a very important role in removing waste products, excess nutrients and fluid from your body by filtering your blood. There are millions of tiny filter units in each kidney that do this. Any waste and excess fluid filtered out by the kidney are removed from your body in your urine. If you have diabetes, the small blood vessels in your kidneys may become damaged over time. This affects the kidneys’ filtering system, meaning that waste products will build up in your blood, and your body will retain more water and salt than it should (causing weight gain and swelling) and can also cause your blood pressure to rise. You may also have protein in your urine. Over time, this can all lead to kidney damage. So if you have diabetes, keeping your blood glucose levels controlled, and having annual tests to monitor your kidney function, can help prevent severe kidney disease.

Heart disease

Diseases of the blood vessels (arteries) are common in people with diabetes. Atherosclerosis (narrowing or hardening of the arteries) is caused by fat, cholesterol and other substances building up in the walls of arteries to form plaques. This causes the arteries to become narrower and harden.

A diagram of 2 arteries, one healthy and one narrowed by plaque

Atherosclerosis (hardening of the arteries) is a common complication of diabetes. Image:

Clots can form that can block the arteries, disrupting the blood flow to important organs such as the heart and brain. This can cause part of the heart muscle to die, triggering a heart attack (myocardial infarction) or a stroke in the brain. Sometimes a plaque can break away and travel in the blood stream where it can lodge in an artery elsewhere in the body, blocking blood flow. Keeping your blood cholesterol levels low and managing your blood pressure can help to prevent a heart attack or stroke.


Blood is carried to the brain by blood vessels. If the blood supply to the brain is disrupted for any length of time, this can cause a stroke. The blood supply can be disrupted if an artery is blocked by a plaque, or a blood clot, or because the artery bursts. This can be caused when the arteries supplying the brain with blood become narrower and less flexible (atherosclerosis). Well-controlled blood pressure and low cholesterol levels can help to prevent a stroke.

A podiatrist examining the feet of someone with diabetes

People with diabetes often experience foot problems. Image:

Nerve problems (peripheral neuropathies)

Reduced blood circulation to nerves may cause them to become damaged, particularly in the legs and feet, causing numbness.

Foot problems

People with diabetes often experience problems with their feet; for example, wounds that won’t heal. This is because diabetes can affect blood flow to the foot and this reduces the body’s ability to heal foot wounds. Diabetes can also cause damage to nerves in the feet, which means that your ability to feel pain or temperature extremes is reduced, increasing the chance of injury. A podiatrist is a health professional specialising in problems with feet, ankles, knees, legs and hips and can advise on the best way to care for your feet to reduce the risk of injuries and complications.

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