What is diabetes?
Diabetes is a serious, chronic disease characterized by chronic elevation of blood glucose and disturbance of carbohydrate, fat and protein metabolism that occurs either when the pancreas does not produce enough insulin or when the body cannot effectively use the insulin it produces.
Raised blood glucose, a common effect of uncontrolled diabetes, may, over time, lead to serious damage to the heart, blood vessels, eyes, kidneys and nerves. Diabetes is not only a disease in itself, but also an intermediate stage for many other conditions. Diabetes is one of the leading causes of blindness, heart attacks, strokes, renal failure and lower limb amputations worldwide.
What is pre-diabetes?
Pre-diabetes means that the blood sugar levels are higher than normal, but not to the levels to diagnose diabetes. Pre-diabetes is the term used for individuals with IFG and/or IGT and/or HbA1c 5.7-6.4% (39-47 mmol/mol). People with pre-diabetes are more likely to develop diabetes within 10 years and there is also an increased risk for cardiovascular disease.
Main Types of Diabetes
Diabetes can be classified into the following general categories:
- Type 1 diabetes (T1D) (due to autoimmune β-cell destruction, usually leading to absolute insulin deficiency). T1D was previously
- Type 2 diabetes (T2D) (due to a progressive loss of β-cell insulin secretion frequently on the background of insulin resistance)
- Gestational diabetes mellitus (GDM) (diabetes diagnosed in the second or third trimester of pregnancy that was not clearly overt diabetes prior to gestation)
- Specific types of diabetes due to other causes, e.g., monogenic diabetes syndromes (such as neonatal diabetes and maturity-onset diabetes of the young [MODY]), diseases of the exocrine pancreas (such as cystic fibrosis), and drug- or chemical-induced diabetes (such as with glucocorticoid use, in the treatment of HIV/AIDS, or after organ transplantation)
Type 1 Diabetes
T1D is caused by an autoimmune reaction, in which the body´s defense system attacks the insulin –producing beta cells in the pancreas. As a result, the body can no longer produce the insulin it needs.
The disease can affect people of any age, but onset usually occurs in children and young adults. Type 1 diabetics need insulin every day in order to control the levels of glucose in their blood. Without insulin the person would die.
Diabetes type 1 develops suddenly and has following symptoms:
- Abnormal thirst and a very dry mouth
- Frequent urination
- Lack of energy, extreme tiredness
- Constant hunger
- Sudden weight loss
- Blurred vision
Diabetes type 1 is diagnosed by an elevated blood glucose level in the presence of the symptoms above. This type of diabetes is increasing. Not clear why, but it may be due to changes in environmental risk factors and/or viral infections.
Type 2 Diabetes
Type 2 diabetes is the most common type of diabetes. Usually occurs in adults but is increasingly seen in children and adolescents. The body is able to produce insulin but becomes resistant so that the insulin is ineffective. Over time, insulin levels may become insufficient. Insulin resistance and deficiency lead to high blood glucose levels.
Symptoms of type 2 diabetes include:
- Frequent urination
- Excessive thirst
- Weight loss
- Blurred vision
The symptoms for T2D are usually less obvious so people with type 2 diabetes remain unaware of their condition for a long time and it may take years to be diagnosed. However, during this time the body is already being damaged by excess blood glucose.
The most important risk factors are excess body weight, physical inactivity, and poor nutrition. Other factors which play a role are ethnicity, family history of diabetes, past history of gestational diabetes and advancing age.
T2D do not require daily insulin treatment to survive. Adopting a healthy diet, increased physical activity and maintenance of a normal body weight are some of the cornerstones of treatment. Oral medications are available to control blood glucose levels and if the levels continue to rise insulin might be necessary.
The number of people with type 2 diabetes is growing rapidly worldwide and is associated with ageing populations, the economic development, increasing urbanization, less healthy diets and reduced physical activity.
Gestational diabetes is a temporary condition that occurs in pregnancy and carries longterm risk of type 2 diabetes. Hyperglycameia that is first detected at any time during pregnancy is classified as either:
- Gestational diabetes mellitus
- Diabetes mellitus in pregnancy
Slightly elevated blood glucose levels during pregnancy are classified as gestational diabetes. Substantially elevated blood glucose are classified as diabetes mellitus in pregnancy.
Symptoms may include increased thirst and frequent urination. It is recommended to screen using oral glucose tolerance test early in pregnancy for high risk women and between the 24th and 28th week of pregnancy in all other women.
Women with hyperglycaemia during pregnancy can control their blood glucose levels through a healthy diet, gentle exercise and blood glucose monitoring. In some cases, insulin or oral medication may also be prescribed.
Even if gestational diabetes normally disappear after birth, women who have been previously diagnosed are at higher risk of developing type 2 diabetes later in life.
Impaired glucose tolerance and impaired fasting glucose
Raised blood glucose levels that are not high enough for diabetes diagnosis are sometimes called pre-diabetes. Impaired glucose tolerance (IGT) or impaired fasting glucose (IFG) are intermediate conditions in the transition between normal blood glucose levels and diabetes, especially type 2 diabetes. People with impaired glucose tolerance are at increased risk of developing type 2 diabetes. Lifestyle interventions such as healthy diet and physical exercise can prevent the progression to diabetes.
Which tests are used to diagnose diabetes and pre-diabetes?
There are three types of tests routinely performed to diagnose pre-diabetes and diabetes.
- Fasting Plasma Glucose Test (FPG) Just prior to having this test run, the patient must fast (nothing to eat or drink except water) for eight hours. The health care provider draws blood from the patient. Then the plasma (the fluid part of the blood) is combined with other substances to determine the amount of glucose in the plasma, as measured in mg/dL. The chart below contains the FPG test's blood glucose ranges for prediabetes and diabetes and describes what each diagnosis means.
- HbA1C (A1C or glycosylated hemoglobin test) The A1C test can be used for the diagnosis of both prediabetes and diabetes. The average blood glucose for the past 2 to 3 months is measured with HbA1c. This test is more convenient because no fasting is required. An A1C of 5.7% to 6.4% means that there is a high risk for the development of diabetes and that the patient has pre-diabetes. Diabetes is diagnosed when the A1C is 6.5% or higher.
- Oral Glucose Tolerance Test (OGTT) The test measures how well the body handles a standard amount of glucose. The health care provider draws the patient's blood before and two hours after the patient drinks a large, premeasured beverage containing glucose. Then, the doctor can compare the before-and-after glucose levels contained in the person's plasma to see how well the body processed the sugar. These levels are measured in mg/dL. The chart below contains the OGTT's blood glucose ranges for prediabetes and diabetes and describes what each diagnosis means.
How can diabetes be monitored?;
Except the home monitoring, performed by the patient at home, the most common test for type 2 diabetes is the HbA1c. The HbA1c (A1C or glycosylated hemoglobin) test provides a picture of the average blood sugar control for the past two to three months. Blood sugar is measured by the amount of glycosylated hemoglobin (A1C) in the blood.
What is glycated hemoglobin (HbA1c)?
Glucose binds to a specific part of hemoglobin and HbA1c (Hemoglobin A1c), glycated hemoglobin is formed. Initially, the reaction between glucose and hemoglobin is reversible (labile HbA1c), but ultimately an irreversible and stable HbA1c is formed. The average life span of red blood cells is 2-3 months. HbA1c reflects the average blood sugar control for the past two to three months.
For a given HbA1c level, the preceding 30 days contribute substantially more (50%) to the HbA1c level, than glucose levels 90-120 days earlier (10%). It does not take 120 days to detect a clinically meaningful change. ~94% of total hemoglobin is non-glycated while ~6% is glycated, ~5% of glycated hemoglobin is HbA1c.
How can HbA1c measurement aid diabetes management?
It can improve diabetes decision making, patient compliance and outcomes. HbA1c is widely used as the most important marker for routine monitoring of long-term glycemic status in patients with diabetes. HbA1c is used as measure of future risk for the development of diabetes complications. HbA1c or Fasting Plasma Glucose (FPG) is measured for diagnosing diabetes.