Type 1 vs. Type 2 Diabetes: Differences

People who have type 2 diabetes can still produce insulin but do so relatively inadequately for their body's needs.

The underlying causes of type 1 and type 2 are different.

Type 1 diabetes causes

Type 1 diabetes is believed to be due to an autoimmune process, in which the body's immune system mistakenly targets its tissues (islet cells in the pancreas). In people with type 1 diabetes, the beta cells of the pancreas that are responsible for insulin production are attacked by the misdirected immune system. This tendency for the immune system to destroy the beta cells of the pancreas is likely to be, at least in part, genetically inherited, although the exact reasons that this process happens are not fully understood.

Exposure to certain viral infections (mumps and Coxsackie viruses) or other environmental toxins have been suggested as possible reasons why the abnormal antibody responses develop that cause damage to the pancreas cells.

Type 2 diabetes causes

The primary problem in type 2 diabetes is the inability of the body's cells to use insulin properly and efficiently, leading to hyperglycemia (high blood sugar) and diabetes. This problem affects mostly the cells of muscle and fat tissues and results in a condition known as insulin resistance. In type 2 diabetes, there also is a steady decline of beta cells that worsens the process of elevated blood sugars. In the beginning, if someone is resistant to insulin, the body can at least partially increase the production of insulin enough to overcome the level of resistance. Over time, if production decreases and enough insulin cannot be released, blood sugar levels rise. In many cases, this means the pancreas produces larger than normal quantities of insulin, but the body is not able to use it effectively. A major feature of type 2 diabetes is a lack of sensitivity to insulin by the cells of the body (particularly fat and muscle cells).

Both diabetes type 1 and diabetes type 2, require good control over their diet by eating foods that help regulate blood sugar, exercise, and in most patients, medical treatments to allow the patient to remain in good health.

Diabetes mellitus is a group of metabolic diseases, all of which have in common high blood sugar (glucose) levels that result from problems with insulin secretion, its action, or both. Normally, blood glucose levels are tightly controlled by a hormone produced by the pancreas known as insulin. When blood glucose levels rise (for example, after eating food), insulin is released from the pancreas to normalize the glucose level.

An absolute lack of insulin, usually due to the destruction of the insulin-producing beta cells of the pancreas, is the main problem in type 1 diabetes.

Type 1 diabetes was formerly referred to as juvenile diabetes or insulin-dependent diabetes mellitus (IDDM). Its causes are different from type II diabetes, as will be reviewed in this article.

Type 2 diabetes was previously called non-insulin-dependent diabetes mellitus (NIDDM), or adult-onset diabetes mellitus (AODM). People who have type 2 diabetes can still produce insulin but do so relatively inadequately for their body's needs. Type 2 diabetes typically occurs in individuals over 30 years of age, and its incidence increases with advancing age. In contrast, type 1 diabetes is most often diagnosed in young people.

Genetics plays a role in the development of type 2 diabetes, and having a family history and close relatives with the condition increases your risk; however, there are other risk factors, with obesity being the most significant. There is a direct relationship between the degree of obesity and the risk of developing type 2 diabetes for both children and adults. It has been estimated that the risk of developing type 2 diabetes doubles for every 20% increase over desirable body weight.

For both type 1 and type 2, early symptoms of untreated diabetes arise due to elevated blood sugar levels and the presence of glucose in the urine.

There isn't a difference between the symptoms of either disease. The "classic" symptoms are the same for both diabetes type 1 and type 2:

• Increased urine output (polyuria)
• Increased thirst (polydipsia)
• Increased hunger (Polyphagia )
• Unexplained weight loss

For both type 1 and type 2, early symptoms of untreated diabetes arise due to elevated blood sugar levels and the presence of glucose in the urine. High amounts of glucose in the urine can cause increased urine output and dehydration. Dehydration, in turn, causes increased thirst.

A lack of insulin or an inability of insulin to work properly affects protein, fat, and carbohydrate metabolism. Insulin normally encourages the storage of fat and protein, so when there is inadequate insulin or poorly functioning insulin, this eventually leads to weight loss despite an increase in appetite.

Some untreated diabetes patients also experience generalized symptoms like fatigue, nausea, and vomiting. People with diabetes are also at risk for infections of the bladder, skin, and vaginal areas. Changes in blood glucose levels can lead to blurred vision. When blood sugar levels are extremely high, lethargy and coma can result.

Signs and symptoms of diabetes, whether type 1 or type 2, do not differ.

• Early diabetes may not produce any symptoms at all.
• When symptoms do occur, the age of onset is typically different, with type 1 diabetes being diagnosed most often in younger people (in a child, for example), while type 2 diabetes is diagnosed more commonly in adults. However, this is not always the case.
• The increasing incidence of obesity among children and adolescents has caused a rise in the development of type 2 diabetes in young people.
• Further, some adults with diabetes may be diagnosed with a form of late-onset type 1 diabetes.

It has been estimated that over 9% of the US population had diabetes in 2012. This corresponds to about 29.1 million people.

Type 1 diabetes is much less common and affects about 1.25 million people. It is further estimated that of the 29.1 million people affected with diabetes, about 8.1 million people are undiagnosed, meaning that they have diabetes but are not aware of it. There has been an increase in the number of Americans with prediabetes. In 2010, 79 million people were estimated to have prediabetes. In 2012, this number was 86 million.

A fasting blood sugar measurement can be used to diagnose any type of diabetes. This test measures the level of sugar (glucose) in the bloodstream in the morning before eating breakfast. Normal fasting plasma glucose levels are less than 100 milligrams per deciliter (mg/dl). Fasting plasma glucose levels of more than 126 mg/dl on two or more tests on different days indicate diabetes. A random (non-fasting) blood glucose test can also be used to diagnose diabetes. A blood glucose level of 200 mg/dl or higher indicates diabetes.

Another test that is often used is a blood test to measure levels of glycated hemoglobin (hemoglobin A1c). This test provides a measure of the average levels of blood glucose over the past 3 months. Other names for the A1C test are the HbA1C and glycosylated hemoglobin tests.

Tests to identify the abnormal antibodies produced by the immune system are used to diagnose type 1 diabetes. Some of the antibodies seen in type 1 diabetes include anti-islet cell antibodies, anti-insulin antibodies, and anti-glutamic decarboxylase antibodies.

• Type 1 treatment: Insulin is the treatment of choice for type 1 diabetes because the body responds appropriately to insulin and the problem is a lack of insulin production by the pancreas.
• Type 2 treatment: Treatment for type 2 is more complicated because the body may produce enough insulin but not be able to use this insulin effectively. For many people with prediabetes or early-stage type 2, lifestyle modifications may be sufficient to control the problem. These can include regular physical activity, weight loss, and following a healthy diet plan to avoid becoming obese.

When lifestyle changes are not enough to control blood sugar levels in people with type 2, medications may be added. There are a great many types, or classes, of drugs that are used to treat this form of the disease, and there are too many to list. These drugs often are used in combination.

The classes of drugs include:

• Sulfonylureas, for example, glyburide (DiaBeta) and glipizide (Glucotrol), stimulate the beta cells of the pancreas to produce more insulin.
• Biguanides, for example, metformin (Glucophage), decrease glucose production by the liver.
• Meglitinides, for example, repaglinide (Prandin) and Nateglinide (Starlix), are a drug class that stimulates insulin production. 
• Thiazolidinediones, for example, pioglitazone (Actos) and rosiglitazone (Avandia), lead to more effective insulin action in fat and muscle tissues and also decrease glucose production in the liver
• DPP-IV inhibitors, for example, sitagliptin (Januvia) and linagliptin (Tradjenta), are a newer class of drugs that work by preventing the breakdown of a naturally occurring compound in the body, GLP-1, that reduces blood glucose levels in the body.
• SGLT2 inhibitors, for example, canagliflozin (Invokana) and dapagliflozin (Farxiga), cause excess glucose to be excreted in the urine.
• Alpha-glucosidase inhibitors, for example, acarbose (Precose), act by blocking or slowing the breakdown of starches and sugars after eating.
• Bile acid sequestrants lower blood cholesterol and typically reduce blood sugar in the process.

• Severely elevated blood sugar levels due to an actual lack of insulin or insufficient action of insulin. This leads to conditions called diabetic ketoacidosis or hyperosmolar coma, which can be life-threatening.
• Abnormally low blood sugar levels due to too much insulin or other glucose-lowering medications.

Long-term complications of either type are related to damage to blood vessels. These complications generally are referred to as small vessel disease, involving the eyes, kidneys, and nerves, and large vessel disease, involving the heart and blood vessels. For example, diabetic neuropathy refers to damage to the nerves that can cause numbness and tingling, among other symptoms. Any type of diabetes accelerates blood vessel damage due to hardening of the arteries (atherosclerosis), leading to coronary heart disease (angina or heart attack), strokes, and pain in the lower extremities because of lack of blood supply (claudication).

There is no known way to prevent type 1 diabetes, and for some people, it might not be possible to prevent the development of type 2. For others, maintaining a healthy weight, getting regular exercise, and a healthy, balanced diet may help prevent or delay the onset of type 2 diabetes and thus preserve health.

This depends upon the individual, including any other health conditions that are present and whether complications of diabetes have developed. Because of the development of complications, studies have shown that on average, those with type 1 diabetes have a life expectancy that is still 12 years below the average.

Other studies have shown that type 2 diabetes also reduces average life expectancy. It's important to remember that these are only averages based on people who have had diabetes in the past and may be affected by including people who do not receive medical care or who have poor control over their diabetes. Advances in modern treatments are likely to reduce these gaps, and taking steps to make sure your diabetes is well controlled and leading a healthy lifestyle can further reduce the risk of death from complications.