Complications of Type 2 Diabetes Mellitus: From Microangiopathy to Diabetic Foot

Type 2 diabetes mellitus can remain asymptomatic for a long time, but even in the absence of obvious complaints, destructive processes occur in the body. The main targets of chronic hyperglycemia (high blood sugar levels) are the blood vessels and the nervous system.

All complications are divided into acute (requiring urgent care) and chronic (developing over years).

1. Acute Complications

These conditions occur suddenly, against the background of diabetes decompensation. They are dangerous due to the risk of coma and death.

• Hyperglycemic (hyperosmolar) coma.
  More common in elderly patients with type 2 diabetes. It develops gradually (over days to weeks) due to severe dehydration. Blood glucose levels reach critical values (sometimes 30–40 mmol/L or higher), but ketone bodies (acetone) are absent. Symptoms include intense thirst, weakness, seizures, drowsiness progressing to loss of consciousness.
• Lactic acidosis coma.
  A rare but the most dangerous complication. It occurs due to the accumulation of lactic acid (lactate) in the blood. It is often triggered by alcohol intake, heart or kidney failure, or the use of certain glucose-lowering drugs (e.g., metformin) in the presence of severe comorbidities. Mortality is very high.
• Hypoglycemic coma.
  A condition caused by a sharp drop in blood glucose (below 3.0 mmol/L). Although more commonly associated with insulin, hypoglycemia in type 2 diabetes can occur as a side effect of sulfonylureas or due to insulin overdose. Symptoms include sudden hunger, tremor, sweating, palpitations, confusion, and loss of consciousness.

2. Chronic (Vascular) Complications

Chronic complications are the main cause of disability in patients. They are divided into microangiopathies (damage to small vessels) and macroangiopathies (damage to large arteries).

Microangiopathies (affecting eyes, kidneys, nerves)

These are specific complications characteristic of diabetes. High glucose levels make small vessel walls fragile and impair tissue nutrition.

1. Diabetic retinopathy (damage to the retina).
   This is the leading cause of blindness among working-age adults. In early stages (non-proliferative), microaneurysms and hemorrhages appear in the fundus. As the disease progresses (proliferative stage), new, fragile vessels form and easily rupture, leading to retinal detachment and glaucoma. The danger lies in the fact that patients may not notice vision deterioration until irreversible changes occur.
2. Diabetic nephropathy (kidney damage).
   Type 2 diabetes is the leading cause of chronic kidney disease (CKD). It begins with microalbuminuria (small amounts of protein in urine), progresses to proteinuria (massive protein loss), and eventually leads to end-stage renal disease requiring dialysis or kidney transplantation. Diabetic nephropathy often remains asymptomatic for a long time and is detected at late stages.
3. Diabetic neuropathy (damage to the nervous system).
   This is the most common complication. Both peripheral nerves (limbs) and the autonomic nervous system can be affected.
   • Peripheral neuropathy: manifests as the “glove and stocking” syndrome (numbness, burning, tingling, loss of sensation in the feet and hands). Loss of sensation is particularly dangerous, as patients do not feel pain from minor injuries, cuts, or burns, leading to trophic ulcers.
   • Autonomic neuropathy: affects internal organs. It may present as gastroparesis (delayed gastric emptying), diarrhea or constipation, orthostatic hypotension (a sudden drop in blood pressure upon standing), erectile dysfunction in men, and painless myocardial infarction.

Macroangiopathies (damage to large vessels)

In type 2 diabetes, atherosclerosis develops 10–15 years earlier than in people without diabetes and progresses more aggressively.

• Coronary artery disease (CAD).
  The risk of myocardial infarction is increased 2–4 times in diabetic patients. A notable feature is the frequent occurrence of “silent ischemia” due to coexisting neuropathy. A heart attack may occur without typical chest pain, presenting only as weakness or shortness of breath, making timely diagnosis difficult.
• Cerebrovascular disease.
  There is a high risk of ischemic stroke. Hyperglycemia worsens recovery outcomes after stroke.
• Diabetic foot syndrome.
  One of the most severe complications, combining neuropathy, ischemia (impaired blood flow in the legs), and infection. Due to loss of sensation and poor circulation, even minor injuries or cracks in the heel can develop into non-healing ulcers. Diabetic foot syndrome is the leading cause of non-traumatic lower-limb amputations.

3. Other Complications and Associated Conditions

• Infections.
  High blood glucose provides an ideal environment for bacterial growth. Patients with diabetes often suffer from urinary tract infections, furunculosis, and fungal infections of the skin and nails.
• Osteoporosis.
  Type 2 diabetes is associated with impaired bone metabolism, increasing the risk of fractures.
• Non-alcoholic fatty liver disease (NAFLD).
  Type 2 diabetes and fatty liver disease often coexist, forming a vicious cycle that can lead to cirrhosis.

How to Reduce the Risk of Complications

The development of most of these conditions can be prevented or significantly delayed. Prevention is based on three key principles:

1. Continuous glycemic control.
   Maintaining glycated hemoglobin (HbA1c) at target levels (usually <7.0%) reduces the risk of microangiopathy by 25–40%.
2. Control of blood pressure and cholesterol.
   For diabetic patients, the target blood pressure is usually below 130/80 mmHg. Statin therapy is recommended even with normal cholesterol levels if cardiovascular risk is high.
3. Regular screening.
   A patient with diabetes should undergo at least once a year:
   • Fundus examination (ophthalmologist);
   • Urine test for microalbuminuria for early detection of nephropathy;
   • Foot examination (by a surgeon or endocrinologist) with assessment of arterial pulses and sensitivity.

Important:
Type 2 diabetes is not a sentence but a specific lifestyle. Modern medicine offers effective tools (glucose-lowering drugs with nephro- and cardioprotective properties, new types of insulin) that, when prescribed in a timely manner, allow patients to maintain a high quality of life for many years.