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Understanding Diabetes Mellitus

Updated on October 27, 2012

The Diabetes Mellitus (DM) is a chronic metabolic disorder, caused by a high level of sugar in the blood. Most of the food we eat is broken down into glucose and released into the blood stream. The glucose is the principal source of energy and is utilized for various functions of our body.

Insulin is a hormone produced and secreted by the pancreas. Once there is a high level of glucose after eating, the pancreas is stimulated to secrete a proportionate quantity of insulin, which is released into the blood stream. Insulin helps our body cells to consume the excess glucose present in the bloodstream and thus keeps the blood sugar level in the normal range.

Etiology of different types of diabetes-

The disease occurs when there is a decreased production or no production of insulin by the pancreas or the body cannot utilize enough insulin due to a reason.

Type-1 diabetes- Also called Insulin Dependent Diabetes Mellitus (IDDM), Type 1 Diabetes affects 0.3% on an average. Its causes are as follows-

  • Genetics and family history
  • Diseases of pancreas
  • Rare viral infections of pancreas
  • Auto-immune reaction

Type-2 diabetes- Also called Non-Insulin Dependent Diabetes Mellitus (NIDDM) or adult onset diabetes; it occurs when the body produces enough insulin but cannot utilize it effectively. Its causes are as follows-

  • Age- more common after 45 years
  • Obesity- it is the single best predictor of type-2 diabetes
  • Ethnicity- it is common in Hispanic and Latin Americans, African Americans, Native Americans and Asian Americans. In fact, not a single community worldwide is free from it.
  • Sedentary lifestyle
  • Pre-diabetes or impaired glucose tolerance
  • Insulin resistance
  • High blood pressure
  • Gestational diabetes- if one develops diabetes during pregnancy, one is said to have gestational diabetes. Such women are more likely to have it later.
  • Polycystic ovary syndrome
  • Anxiety, tension and stress

Gestational Diabetes- Also called Gestational Diabetes Mellitus (GDM), it is triggered by pregnancy and is caused by hormones produced by placenta during pregnancy. Its causes are as follows-

  • Obesity
  • Family history
  • Age- older women are more prone to develop it.
  • Previous glucose intolerance or previous gestational diabetes


It is diagnosed by performing oral glucose tolerance test (OGTT). First fasting blood glucose after an overnight fast of eight hours is measured and then two hour post-prandial after OGTT is measured.

The categories of fasting blood glucose are shown below.

  • Normal blood glucose Fasting blood glucose < 100 mg/dl (5.6 mmol/l)
  • Impaired fasting blood glucose Fasting blood glucose 100-125 mg/dl (5.6-6.9 mmol/l)
  • Provisional diagnosis of diabetes Fasting blood glucose > 126 mg/dl (7.0 mmol/l)

The categories of two hour post-prandial blood glucose corresponding to above are shown below.

  • Normal glucose tolerance 2-h PP blood glucose < 140/dl (7.8 mmol/l)
  • Impaired glucose tolerance 2-h PP blood glucose 140-199 mg/dl (7.8-11.1 mmol/l)
  • Diabetes 2-h PP blood glucose > 200 mg/dl (11.1 mmol/l)

(2-h PP blood glucose = 2 hour post prandial blood glucose)

Glycosylated hemoglobin (HbA1c) is another test done for the diagnosis and determination of control of the disease. Glucose sticks to the hemoglobin of the blood to form glycosylated hemoglobin (hemoglobin A1c or HbA1c). The more glucose present in the blood, the more will be level of HbA1c present in the blood. Red blood cells live for 8 to 12 weeks before they are replaced. The measurement of HbA1c will tell how high the blood glucose level was over the past 8 to 12 weeks.

  • Normal non diabetic HbA1c 3.5-5.5 %
  • In diabetes good control HbA1c 6.5 %
  • In diabetes poor control HbA1c above 6.5%

Some experts set the target from 7% to 7.5% depending upon the severity of the disease of the individual and HbA1c above 7.5% indicates poor control according to them.

Diabetes may be diagnosed on the basis of HbA1c as shown below.

  • Diabetes HbA1c > 6.5%
  • Non diabetic HbA1c = 6.0
  • Pre-diabetes or at risk of diabetes HbA1c between 6.0-6.5%


This is a distinct clinical entity. When blood glucose level is higher than normal but is not high enough to be diagnosed as diabetes, it is termed pre-diabetes. The incidence of pre-diabetes is growing rapidly. People having pre-diabetes have no symptoms but they are at a higher risk to develop full fledged diabetes. With prediabetes, people are at a 50% higher risk of developnig heart disease and stroke. Prediabetes should not be ignored but it signals the likely onset of a more serious disease.

It is diagnosed as shown below.

  • Fasting blood glucose 100-125 mg/dl (5.6-6.9 mmol/l)
  • 2-h PP blood glucose 140-199 mg/dl (7.8-11.1 mmol/l)
  • HbA1c between 6.0-6.5%

Since diabetes has become an ever increasing global epidemic, every individual should try to understand the basics of the disease in order to either prevent it if not suffering from it or manage it efficiently if suffering from it.


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