Long Term Complications

This page has in part been reproduced from the earlier summary, "Introducing Complications". The various conditions are considered in further detail here in each of the subsections (see menu on left side bar).

What's covered on this page

What Are 'Diabetic Complications'?

Summary Table

Why Do These Conditions Develop?


What Are ‘Diabetic Complications’?

The expression 'long term complications of diabetes' refers to a multitude of health problems that often develop in people with diabetes, as a result of having diabetes. Some conditions are specific to diabetes, however, some conditions also occur in people who do not have diabetes.

As treatment strategies have improved, people with diabetes are living longer and the long term effects of diabetes on the body have become apparent. Not all people with diabetes will go on to develop complications, but most are affected to some degree. Many people with Type 2 diabetes already have some degree of complications when they are diagnosed.

Diabetes takes its toll in the form of damage to numerous body tissues, including the eyes, nerves, kidneys and heart. These ‘complications’ are chiefly the result of damaged blood vessels.



Summary of Complications

Clinical term

Affected body tissue

What does it mean?

Microvascular damage. This is damage to small blood vessels and plays a part in complications of the eyes, nerves and kidneys.



The small blood vessels at the back of the eye (retina) become damaged. Fluid and other components from blood leak into the eye, blurring vision.

As this condition progresses, new fragile blood vessels start to form (proliferation). These grow forwards and bleed into the clear jelly-like part of the eye through which we see. In addition, fibrous scar tissue may form which shrinks, tearing the retina apart. If left untreated, proliferative retinopathy can result in blindness.



Nerves allow body cells to communicate with the brain. Blood vessels supply the nerve cells with oxygen and nutrients. When these become damaged, nerves are starved and do not function properly. Electrical messages through the nerves are interfered with, or stopped altogether.

Damage to nerves may lead to any of a number of problems including:

  • loss of sensation in the hands or feet
  • urinary problems such as incontinence
  • sexual problems such as impotence
  • digestive problems
  • dizziness
  • uncontrolled sweating
  • lack of recognition of hypos

Damage to blood vessels and nerves in the feet can lead to ulcers and amputation.



The kidneys rid the body of undesirable toxins by passing blood through many tiny filtering units (glomeruli). Damaged small blood vessels can prevent the glomeruli from working properly. In the early stages of kidney disease small amounts of blood protein (albumin) begin to leak through into the urine. This condition is called microalbuminuria (micro-albumin-urea) and is usually the first stage of kidney disease to be detected.

As the condition progresses (this may be over many years), the kidneys lose their ability to filter waste products from the blood, and more protein is leaked out. Sometimes people develop high blood pressure.

If the damage becomes severe then the toxins may build up in the blood to dangerous levels (kidney failure). Then toxins need to be removed from the blood artificially by dialysis. Some patients may go on to have a kidney transplant.

Macrovascular damage leading to cardiovascular disease. This is damage to the main blood vessels and is involved with ‘hardening of the arteries’ (atherosclerosis) and heart disease.


Blood vessels

Deposits form on vessel walls, narrowing them. As vessels become clogged up, blood supply is restricted.

A stoppage of blood flow to the heart can cause a heart attack. A stoppage of blood flow to the brain can cause a stroke.



If blood flow to the heart is slowed for a period of time, this may give a person chest pain.

Hypertension. This is high blood pressure and can contribute to both microvascular and macrovascular disease. High blood pressure puts stress on the heart, meaning it has to work harder. It can also cause a fatty tissue (atheroma) to develop on the insides of blood vessels, narrowing and clogging the vessels.


Why Do These Conditions Develop?

High blood glucose levels

The main feature of diabetes is high blood glucose levels - hyperglycaemia. It is no coincidence that the major factor in diabetes complications is hyperglycaemia. Over time, high blood glucose levels can result in a multitude of effects, and no part of the body escapes totally unharmed.

Importantly though, the damaging effects of high blood glucose levels are not limited to long periods of hyperglycaemia; some effects occur in the short term too - during the blood glucose rise after meals, for example (this is termed 'postprandial hyperglycaemia').

More detailed information on the mechanisms of hyperglycaemic damage can be found in the section on the long term effects of hyperglycaemia.

Other effects of diabetes

Many people with diabetes have different levels of fats or lipids in their bloodstream compared to non-diabetic people (a condition known as dyslipdaemia). High blood pressure (hypertension) is also more common. People with diabetes also tend to have different levels of blood clotting agents. These factors together are likely to contribute to the development of long term complications.

Some factors relating to obesity and insulin resistance may play a part independently of high blood glucose levels in people with Type 2 diabetes, particularly when it comes to macrovascular damage and heart disease.


Not all people with diabetes go on to develop complications in later life. Some people seem to escape them in spite of having blood glucose control which is comparable to that of others who do develop complications. This has led researchers to believe that genes may play a role and studies are underway to investigate this further.

It has also been suggested that high glucose levels in the body may act to turn some genes on or off and this phenomenon may be involved in the development or acceleration of diabetic complications.