The complications of diabetes mellitus have imbibed a fear among the general population because of their serious effects on the body. That is the reason why people have become so much aware of this disease.

If a diabetic patient does not take care of controlling his blood sugar levels, he is at a high risk of developing dangerous health consequences, the end result of which can be crippling and furthermore, even fatal.

Although the health impact of both, diabetes type 1 and type 2 is common, they are more prevalent in type 2 diabetes. And, in both, the risk increases with the duration and the severity of the disease.

The list is long and affects major organs of the body, which include the heart, blood vessels, brain, nerves, eyes, bowels, and kidneys.

Some complications come on early and are short-term. Some come on late, which can be labeled as long-term.

Complications of diabetes type 1 and type 2 

The complications of diabetes explained here can be caused by both diabetes type 1 and type 2.

Some can come on early while some have a gradual and late-onset. Some can cause death while others exist as comorbidities and worsen your lifestyle.

Heart Disease (cardiovascular) and Stroke

The effect of diabetes on the heart is that the diabetic runs double the risk of contracting heart disease or stroke. Chances are that a diabetic, who has had a heart attack once, have a greater risk of getting another one.

Heart disease and stroke account for the greatest proportion of morbidity among diabetic patients with cardiovascular complications accounting for 65% of deaths among diabetics.

Again, mortality rates due to heart disease are up to 4 times higher in diabetics than in people without diabetes.

This is because diabetes and hypertension co-exist in more than 50% of diabetes patients and hypertension is the number one cause of a heart attack.

Secondly, diabetes and high cholesterol often co-exist, and high blood cholesterol is a common cause of a heart attack.

High cholesterol levels in the blood cause fats to be deposited on the inner walls of the blood vessels. These deposits are called plaques.

Consequently, the walls of the blood vessels thicken and harden, which results in clogging of the arteries and reduced blood supply to the heart, greatly increasing the risk of a heart attack. The link between diabetes and heart disease is a proven fact.

Diabetic Retinopathy (Blindness)

Chronic long-standing diabetes gradually damages the retina of the eye. The combination of diabetes and hypertension damage the smaller blood vessels of the eye. These blood vessels get clogged, brittle, and weakened causing them to rupture.

Blood gets released into the vitreous fluid, which fills the eyeball. This fluid loses its transparency and the light rays which enter the eye do not reach the retina, resulting in impairment of vision.

There may be double vision, blurring of vision, or flashing lights or dark spots in front of the eyes. The diabetic patient also experiences pain in both the eyes and peripheral vision is lost.

Diabetes also increases the risk of cataracts and glaucoma. Any of these diabetes eye complications can potentially lead to blindness.

It is imperative, therefore, that a diabetic patient should get his eyes checked regularly.

Diabetic neuropathy – Nerve damage

More than 70% of the patients, with a long history of diabetes, have this complication of diabetic neuropathy. The major risk factor for peripheral neuropathy is hyperglycemia followed by age, duration of disease, smokinghypertension, elevated triglycerides levels, being overweight or obese, and alcohol.

The onset of diabetic polyneuropathy is gradual and may lie undetected for years. Neuropathy symptoms include sensory loss, muscle weakness, burning, numbness, and pain in the legs and feet. The neuropathic pain when present can be so severe so as to stop the person from taking a step.

As explained earlier, uncontrolled diabetes damages blood vessels. As a result of this damage to the small blood vessels, the nerves do not get enough blood supply and diabetic neuropathy can develop. Any nerve or its segment in the body could get affected.

The symptoms of diabetic neuropathy thus depend on the nerve that is affected. The symptoms could, therefore, be peripheral or autonomous.

Peripheral nerve damage or peripheral neuropathy symptoms could thus be those relating to the hands and feet like tingling and numbness, loss of sensation, and a non-healing ulcer on the foot, among other things.

Autonomous nerve damage symptoms could be those relating to the heart or the digestive tract or the kidneys and urinary bladder.

Erectile Dysfunction

Erectile dysfunction is a complication of long-standing diabetes, meaning it comes in late.

As explained earlier, diabetes causes clogging of the arteries and damage to the nerves. Since penile erection depends on a sequence of events in which blood vessels and nerves play an important role, the erection can be hampered.

Erection dysfunction may be partial or total depending on the extent of damage to the blood vessels and the nerves and is a common long-term complication of long-standing diabetes.


Hypoglycemia is a condition wherein the blood sugar levels fall below 70 mg/dcl.– ie. much below the lower normal limit. This is a short-term diabetes complication more commonly seen in diabetics whose blood glucose levels are unstable and vary wildly.

Diabetic nephropathy – kidney damage

The damage caused to the blood vessels and the nerves in diabetes has a heavy toll on the kidneys.

The thickening and clogging of the blood vessels of the kidneys (eg. the renal artery) reduce the blood supply to the kidneys. This impairs the kidneys’ filtration process of the blood. The protein thus leaks into the urine, which is a sign of kidneys beginning to get damaged,

If the nerves supplying the kidney and the urinary tract get damaged, the sensation of the bladder is lost. As a result, the urge to urinate is not felt and the urine collects in the bladder till the bladder becomes full.

The urine passes without the diabetic patient realizing it. This is called urinary incontinence.

Similarly, urine also collects in the kidneys for a long time. This causes infection setting in the kidneys and the bladder.

The kidneys do not function properly and ultimately they fail. Kidney failure is imminent. This is one of those complications of diabetes that can kill.

Digestive complications of diabetes affecting the stomach and bowels

Diabetic neuropathy can affect any or all the nerves, which supply the various parts of the digestive tract. Depending on the nerve and the part it supplies, complications pertaining to that part occur. It could be the stomach or the bowels.

  • The complication of diabetes affecting the esophagus can cause difficulty in swallowing.
  • There is gastroparesis in which the muscles of the stomach do not function properly because of damage to the nerves supplying them. There is inadequate grinding of the food in the stomach and poor emptying of its content into the intestine. As a result of the loss of nervous control in the stomach, food in the stomach empties slowly. Digestion does not take place properly. There is persistent nausea, vomiting, distension of the stomach, and loss of appetite.
  • Levels of glucose fluctuate widely due to improper digestion of food.
  • Due to intestinal complications, constipation alternates with uncontrolled diarrhea giving rise to loss of weight in diabetics.

Foot complications of diabetes – diabetic foot

As explained earlier, in diabetes, two complications occur:

(1) Reduced blood supply due to clogging of arteries (atherosclerosis)

(2) Nerve damage due to reduced blood supply to the nerves (diabetic neuropathy)

As a result of these two complications of diabetes, namely, diabetic neuropathy and atherosclerosis, occurring in the lower extremities, there is reduced sensation and reduced blood supply to the foot. The pain of an injury is not felt, and, therefore, the injury tends to get neglected.

Due to the reduced blood supply to the foot, the white blood cells do not reach the site of injury in sufficient quantity and therefore, the defense mechanism of the body cannot efficiently fight the wound infection.

Moreover, the high glucose content in the blood helps the bacteria to proliferate quickly. Infection spreads and the injury worsens because the medicines given, cannot reach the site of infection through the blood in the full dosage due to the clogged arteries.

The wound deepens and the infection may spread to the bones resulting in osteomyelitis. In serious cases, amputation of the foot or leg may be the only surgical remedy.

Alzheimer’s disease

Diabetes type 2 also increases the risk of Alzheimer’s disease, especially in people with poor sugar control. The poorer the control, the higher is the risk. Theories have been put forward advocating the cause but are yet to be proved.

Other complications

Other complications include dental disease, lowered resistance to infections such as influenza and pneumonia, hearing loss, frequent skin bacterial and fungal infections, and other birth complications in diabetic pregnant women.

Of the complications described above, some can develop early while some complications can appear late. Again, they can be microvascular or macrovascular and episodic or progressive.

Short-term or early complications 

  • hypoglycemia (low blood sugar levels)
  • diabetic ketoacidosis (DKA)
  • hyperosmolar hyperglycemic state (HHS) – a hyperglycemic ion is usually seen in elderly patients with type 2 diabetes and carries higher mortality than diabetic ketoacidosis (DKA)

Long-term or late complications

  • eyes (retinopathy)
  • heart (cardiovascular disease)
  • kidneys (nephropathy)
  • nerves and feet (neuropathy)

Another classification types the complications as microvascular or macrovascular.

Microvascular or microvascular complications

Microvascular complications, which are more prevalent include nervous system damage (neuropathy), renal system damage (nephropathy), and eye damage (retinopathy).

Macrovascular complications include cardiovascular disease, stroke, and peripheral vascular disease. Peripheral vascular disease may lead to bruises or injuries on the feet or legs (diabetic foot) that do not heal leading to gangrene and, ultimately, amputation.

A third way to describe the complication type is episodic and progressive.

Episodic or progressive complications

Again, diabetes complications can be episodic or progressive. Episodic complications are those that can be treated but they keep on recurring (eg, foot ulcers).

Progressive complications have a mild onset, but progress over time causing further irreversible damage to the body organs (eg, nephropathy).

What increases the risk of diabetes complications?

The three most significant factors that increase the risk of diabetes complications include:

  • Hyperglycemia
  • Hypertension
  • Hypercholesterolemia

A diabetic can significantly reduce his risk of complications by keeping these conditions under control.

For example,

  • Each  percentage point reduction in HbA1c level in a person with diabetes can reduce that person’s risk for complications by 40%
  • A 10 mm Hg reduction in blood pressure can reduce that person’s risk by up to 12%
  • Keeping the serum lipids under control can reduce that person’s risk for heart complications by 20% to 50%

Diabetes complications should never be ignored. They can be fatal. Health conditions such as heart disease, stroke, and kidney failure are the most common complications that can cause death.

The best way to prevent any complications is to learn to identify its symptoms and seek prompt treatment, which should be followed religiously. It just doesn’t end there.

Make sure you follow lifestyle advice and stick to the ideal diet for diabetics. And of course, avoid the risk factors that can worsen your diabetes.