Complications of Diabetes

August 23, 2011

Short-term complications

Diabetes can cause medical emergencies in both type 1 and type 2 diabetics when blood glucose levels rise extremely high. This can occur if a diabetic patient does not take her insulin or pills or does not follow a diabetic diet. Infection, heart attack, and other physical stresses can also cause high glucose levels. Extremely high glucose levels lead to loss of glucose in the urine, which pulls water along with it, leading to excessive loss of water from the kidneys. This results in dehydration, which further concentrates glucose in the blood causing glucose levels to rise. Weight loss occurs both as a result of water and calorie loss.

In type 1 diabetes, this scenario can occur abruptly when insulin is severely deficient. A condition called ketoacidosis develops. Blood glucose levels rise to 300-600 mg/dl. Since the cells are now unable to use glucose for fuel, the body starts to break down fat to produce ketoacids. When ketoacid levels rise, the blood becomes acidic, which impairs enzymatic reactions throughout the body. This results in abdominal pain, nausea, and vomiting. Ketones can be detected in the urine and produce a fruity odor on the breath. Brain cells do not use ketones, so they starve in the absence of insulin, producing coma. Diabetic ketoacidosis was universally fatal prior to the discovery of insulin. Now, about 2% of patients with this condition die.

In type 2 diabetes, insulin resistance is the main problem and insulin is not as severely deficient. Therefore, ketoacidosis does not occur. Instead, glucose levels continue to rise to 1,000 mg/dl or more. This produces a condition known as nonketotic hyperosmolar state. With such high glucose levels there is simply too much “stuff” in the blood and water is pulled out of cells to try to dilute the blood back to a normal range. This water is then lost in the urine. Such severe dehydration causes drowsiness, delirium, coma, or seizures. The elderly are more vulnerable, but overall about 20-40% of people with this condition die.

Long-term complications

Improved medical care has made diabetes a chronic disease. Mildly elevated glucose levels can be tolerated in the short term, but over many years damage is done to small blood vessels (microvascular disease) or to large blood vessels (macrovascular disease).

Microvascular complications include blindness from damage to the retina, kidney failure, and nerve damage (neuropathy). Diabetes is the leading cause of blindness in people aged 20-74 years. Diabetes is also the leading cause of kidney failure requiring dialysis, accounting for 43% of new cases. Nerve damage affects 60-70% of diabetics and causes an inability to sense trauma. Because of this, diabetics are prone to unnoticed skin breaks, which can become infected. Diabetic feet especially heal slowly if at all, and many diabetic foot infections ultimately require amputation. Diabetes accounts for more than 60% of all nontraumatic lower limb amputations.

Macrovascular complications include heart disease and stroke. These complications are exacerbated by high blood pressure and high cholesterol, which often go along with diabetes. Heart disease is the leading cause of death in diabetes, occurring 2-4 times more often in diabetics than in nondiabetic individuals. Stroke is also 2-4 times more common in diabetes.

Pregnancy-related complications

Diabetes can cause many problems in pregnancy. In the first trimester, about 5-10% of fetuses develop major birth defects and 15-20% of pregnancies end in miscarriage. During the second to third trimesters, excessive fetal weight gain (macrosomia) occurs, especially in poorly controlled gestational diabetes. This leads to complications during delivery for both the mother and the baby. The goal of diabetic treatment in pregnancy is tight control of glucose levels to reduce the chance of these problems. In gestational diabetes, if glucose levels are not controlled with diet and exercise, then insulin (or sometimes oral medication) is used. Women with preexisting diabetes who become pregnant also need intensive monitoring and treatment.


Patients with diabetes are prone to certain infections in the urinary tract or skin and soft tissue and fungal infections such as vaginal yeast infections. Good glucose control helps prevent infections and may also help with wound healing. About 30% of patients with diabetes also have severe periodontal disease.

SEE ALSO: Cardiovascular disease, Cholesterol, Diet, Hypertension, Nutrition, Obesity

Suggested Reading

  • Brotman, D., & Girod, J. P. (2002). The metabolic syndrome: A tug-ofwar with no winner. Cleveland Clinic Journal of Medicine, 69, 990-994.
  • Haffner, S. (2002). Metabolic syndrome, diabetes and coronary heart disease. International Journal of Clinical Practice (Suppl. 132), 21-37.
  • Nathan, D. M., & Cagliero, E. (2001). Diabetes mellitus. In P. Felig & L. A. Frohman (Eds.), Endocrinology & metabolism (4th ed., pp. 827-926). New York: McGraw-Hill.

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Category: About diabetes