1 Ratings

Diabetes mellitus

Diabetes mellitus
portrait of José Antonio Zumalacárregui Ph.D.
Written by

José Antonio Zumalacárregui Ph.D.
Medically reviewed by our Medical staff

Last update: 20-09-2022

How else can it be called?

  • Diabetes

  • ICD-10: E08

What is diabetes mellitus?

Diabetes mellitus, commonly known as diabetes, is a chronic metabolic disease characterized by a high level of blood sugar (glucose).

Every cell in the human body needs energy in order to function. The main energy source of the body is glucose, a type of sugar that results from the digestion of carbohydrates. Glucose circulates in the blood as a ready energy source for the cells that need it.

Insulin is a hormone produced in the pancreas that lets glucose enter into the cells. In case of suffering from diabetes the pancreas no longer produces insulin or the cells stop responding to the insulin that is produced (tissue resistance to insulin). As a result, there is an accumulation of glucose in the blood. In this way, diabetes is characterized by hyperglycemia that means that there is too much sugar in the blood.

The chronic hyperglycemia of diabetes is often associated with long-term complications damage in multiple organ systems, especially the kidneys, heart, eyes, nerves, and blood vessels.

Increasingly sedentary lifestyles and poor eating habits have contributed to the increase in diabetes worldwide.

Which types of diabetes mellitus are there?

There are three main types of diabetes mellitus:

  • Type 1 diabetes: It is an autoimmune disease characterized by a lack of insulin. The pancreas produces little or no insulin. It accounts for approximately 5% to 10% of all cases. It usually begins in childhood or adolescence and was previously known as insulin-dependent diabetes mellitus (IDDM) or juvenile diabetes.
  • Type 2 diabetes: It is due to an insulin resistance, a decrease in cell metabolic response to insulin that avoids the glucose to enter into the cells. Patients can have a normal concentration of insulin in the blood or even a high level. The problem is that there is a cell resistance to insulin. Approximately 90% to 95% of diabetic patients have type 2 diabetes, and many of them are overweight. It most often develops in adult people and was previously known as noninsulin-dependent diabetes mellitus (NIDDM).
  • Gestational diabetes: It can develop during pregnancy and generally resolves after the baby is delivered. This condition appears in about 2% of pregnancies.

There are other less common types of diabetes such as drug-induced diabetes, the diabetes related to cystic fibrosis or secondary to other diseases (acromegaly, Cushing syndrome or surgical removal of the pancreas).

What are the main causes of diabetes mellitus?

The causes of diabetes mellitus are unclear, however, there seem to be both hereditary and environmental factors involved.

In Type I diabetes, the disease may be triggered by a virus or another microorganism that destroys the cells in the pancreas that produce insulin.

In Type II diabetes, age, obesity, and family history of diabetes are known as risk factors.

How many people can be affected?

Diabetes mellitus can affect between 5 to 6% of the population.

What are the main symptoms of diabetes mellitus?

People with diabetes often have no symptoms for years.

Anyway, the most common symptoms of diabetes mellitus are:

  • Large production of urine or frequent urination (polyuria)
  • Excessive thirst (polydipsia)
  • Excessive or extreme hunger (polyphagia)

Other symptoms can be:

  • Feeling tired and sick
  • Sudden weight loss despite increased appetite
  • Vaginitis, skin infections, blurred vision and bladder and urinary tract infections
  • Occasionally, impotence in men and absence of menstrual period in women

How can it be diagnosed?

Diagnostic criteria for diabetes include the following ones:

  • Glucose in the blood greater than 200 mg/dl (a test at any time of the day)
  • Fasting plasma glucose in the blood greater than 126 mg/dl (fasting should be greater than 8 hours)
  • Glucose greater than 200 mg/dl after 2 hours of an oral glucose tolerance test
  • A glycated hemoglobin (HbA1C) level greater than 6.5%

Any of the criteria above are enough for the diagnosis of diabetes mellitus.

Urine tests can also detect a high level of glucose, ketones and protein (albumin) in the urine that may help diagnose diabetes.

What is the recommended treatment?

Treatment of diabetes focuses on two ultimate goals:

  • Keeping blood glucose within normal range.
  • Preventing the development of long-term complications.

The treatment may differ depending on the type of diabetes:

  • Type 1 diabetes: daily administration of insulin.
  • Type 2 diabetes: diet and exercise should be the first-line therapy in order to lose weight. Most of the patients also require antidiabetic or hypoglycemic drugs (metformin, sulfonylurea) and some also need insulin.
  • Gestational diabetes: it is usually treated by diet, however, sometimes insulin administration is required.

Which are the possible complications?

In case of suffering Type 1 diabetes the main complication is usually diabetic ketoacidosis. The blood may become acidic due to accumulation of ketones if insulin is not properly administered. Symptoms include excessive thirst, abdominal pain, vomiting, rapid breathing, extreme lethargy and drowsiness. Patients with ketoacidosis will also have a sweet breath odor.

In case of suffering Type 2 diabetes the main complication related is diabetic hyperglycemic hyperosmolar syndrome (also called hyperosmolar coma) that has a high mortality (around 20%). The main feature is an extremely high level of glucose in the blood without the presence of ketones. Other features of this syndrome are extreme dehydration and decreased consciousness.

In addition, chronic hyperglycemia can cause long-term complications (they usually appear after 15 or 20 years). The main complications that usually appear are:

  • Vascular complications: people with diabetes have a higher risk to suffer a heart disease or a stroke.
  • Diabetic nephropathy: kidney damage caused by diabetes.
  • Eye problems, including cataracts, glaucoma, and diabetic retinopathy are also more common in diabetics. Diabetes may also cause blindness.
  • Diabetic neuropathy: Damage to the nerves, particularly in the legs and feet.
  • Frequent infections (skin infection, tuberculosis, pneumonia, pyelonephritis, etc.).
Medically reviewed by our Medical staff on 20-09-2022


  • Textbook of diabetes 5th edition. 2017. Richard Holt, Clive Cockram, Allan Flybjerg, Barry Goldstein. ISBN 9781118924877.
  • First Aid for the Basic Sciences: Organ Systems (3rd Ed) 2017, Tao Le, William L. Hwang, Vinayak Muralidhar, Jared A. White and M. Scott Moore, ISBN: 978-1-25-958704-7, Pag. 162.
  • Robbins Basic Pathology (10th Ed) 2018, Vinay Kumar, Abul K. Abbas, Jon C. Aster, ISBN: 978-0-323-35317-5, Pag. 772.
  • The Gale Encyclopedia of medicine. Second Edition. Jacqueline L. Longe. Vol 2. pag 1047. ISBN 0-7876-5491-4.
  • Diabetes. World health organization. Available on: https://www.who.int
  • Inzucchi SE. Clinical presentation, diagnosis, and initial evaluation of diabetes mellitus in adults. UptoDate. 2023. Available on: https://www.uptodate.com

Show more

Rating Overview

Share your thoughts about this content

E-mail (Optional):
Add a review