What Is Diabetes Mellitus?

In This Article

Diabetes mellitus is a group of diseases that affect the body's ability to control blood sugar. It is characterized by defects in insulin secretion, insulin action, or both. There are several different types of diabetes, and some experts believe even subcategories of diabetes mellitus within specific groups.

The word "diabetes" originates from AD Greek physician Aretus the Cappadocian and translates to mean "a passer through, a siphon." Aretus is responsible for labeling the condition associated with polyuria or excessive urination. People with diabetes were known to pass water like a siphon.

The word "mellitus", which translates as "honey, sweet" was coined later by Thomas Willis (Britain) in 1675 after rediscovering the sweetness of urine and blood of patients (first noticed in ancient India).

Although diabetes mellitus and diabetes insipidus share the same name Latin name "diabetes", they are not the same. The term insipidus, in Latin, means tasteless.

Type of Diabetes Mellitus

According to the American Diabetes Association, "Assigning a type of diabetes to an individual often depends on the circumstances present at the time of diagnosis, and many people with diabetes do not easily fit into a single class."

The American Diabetes Association classifies diabetes into the following general categories:

  • Type 1 diabetes: Due to autoimmune β-cell destruction, usually leading to absolute insulin deficiency
  • Type 2 diabetes: Due to a progressive loss of adequate β-cell insulin secretion frequently on the background of insulin resistance
  • Gestational diabetes mellitus: 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: Monogenic diabetes syndromes, diseases of the exocrine pancreas (such as cystic fibrosis and pancreatitis), and drug- or chemical-induced diabetes (such as with glucocorticoid use, in the treatment of HIV/AIDS, or after organ transplantation)

Prediabetes

While prediabetes is not necessarily classified as a type of diabetes, it's important to know about it because approximately 88 million American adults—more than 1 in 3—have prediabetes. Of those with prediabetes, more than 84% don’t know they have it.

Prediabetes, a condition that is also described as impaired glucose tolerance (IGT) or impaired fasting glucose (IFG), is considered a precursor of type 2 diabetes. Prediabetes does not typically cause symptoms, but without intervention, it can progress to type 2 diabetes.

If you have prediabetes, you probably make enough insulin, but the cells of your body are resistant to insulin and its effects. Insulin is the hormone that takes sugar from the blood to the cells for energy.

When your cells are resistant to insulin, glucose or sugar remains in the blood, as opposed to being taken to the cells. This results in a slightly elevated blood glucose level, as well as decreased energy. In addition, the body may actually begin to make more insulin, which overworks the pancreas and exacerbates the situation, causing high insulin levels.

Dietary management, weight loss, and exercise are often effective for treating prediabetes—but sometimes medication is needed. The goal for people with prediabetes should be to avoid developing type 2 diabetes.

Type 1 Diabetes

Type 1 diabetes is an autoimmune disease that affects the pancreas and accounts for only 5–10% of those with diabetes. It occurs when the body’s immune system attacks the insulin-producing beta cells in the pancreas and destroys them.

People with type 1 diabetes do not make insulin and need to take insulin via injection or infusion so that they can maintain blood sugar control and utilize carbohydrates for energy. Elevated blood sugar resulting in weight loss, excessive hunger, excessive thirst, and bed-wetting in children are signs of type 1 diabetes.

To validate a diagnosis, physicians will test for antibodies, proteins that help the body protect itself from “foreign” substances such as bacteria or viruses. People with type 1 diabetes have antibodies that destroy the body’s insulin-making beta cells.

This disease typically affects younger people and was once called juvenile diabetes, but can occur also occur in adulthood. The rate at which the beta cells die typically occurs more rapidly in children then adults.

Sometimes children will get diagnosed with type 1 diabetes and have a honeymoon period, otherwise known as a remission, in which the pancreas may still secrete some insulin. This time can last weeks, months, or even up to year in some instances. However, over time the pancreas stops working altogether and insulin needs increase.

Type 2 Diabetes

Type 2 diabetes is a chronic disease in which the body is unable to adequately control the levels of glucose (sugar) in the blood, which can lead to dangerously high blood glucose (hyperglycemia). It accounts for approximately 90% to 95% of those with diabetes.

The CDC says, "Type 2 diabetes most often develops in people over age 45, but more and more children, teens, and young adults are also developing it." The disease is marked by an increase in blood sugar (glucose) levels and heightened resistance to the hormone insulin, which shuttles glucose into the cells.

Type 2 diabetes is a highly prevalent condition with numerous risk factors. The American Diabetes Association says, "Most patients with this form of diabetes are obese, and obesity itself causes some degree of insulin resistance. Patients who are not obese by traditional weight criteria may have an increased percentage of body fat distributed predominantly in the abdominal region."

The risk of developing this form of diabetes increases with age, obesity, and lack of physical activity. People who have had gestational diabetes or those with high blood pressure (hypertension), cholesterol or triglycerides (dyslipidemia) are also at increased risk.

Type 2 diabetes has a stronger genetic predisposition than type 1 diabetes, but the genetics are complex and not fully defined.

Most of the time, weight loss and lifestyle modification can improve blood glucose levels by decreasing insulin resistance. Depending on how high blood glucose levels are at diagnosis people with type 2 diabetes may need medication.

Gestational Diabetes

Gestational diabetes develops during pregnancy when the pancreas cannot accommodate for insulin resistance, which is common during pregnancy due to placental secretion of hormones. In the United States, about 6% to 9% of people who are pregnant develop gestational diabetes.

When the cells are resistant to insulin, sugar or glucose accumulates in the blood. People who are diagnosed with gestational diabetes do not have diabetes before they are pregnant.

If a person has gestational diabetes for one pregnancy they may have it again for other births. This type of diabetes usually shows up in the middle of pregnancy and people are screened for it between 24 and 28 weeks.

People who are overweight before pregnancy or those with diabetes in the family tend to be more prone to gestational diabetes, but this isn't always the case. In addition, it is more common in people who are Native American, Alaskan Native, Hispanic, Asian, and Black, but is also found in those who are White.

It is important to treat gestational diabetes as soon as it is diagnosed. Keeping blood sugars within normal range will help to prevent any complications, such as having a cesarean delivery, a baby born too large, and developing obesity or type 2 diabetes later in life.

Treatment usually includes changes to diet, specifically following a carbohydrate-controlled diet. Carbohydrates are the nutrients that impact blood sugars the most. Careful blood glucose monitoring will also help people with gestational diabetes to keep their blood sugars in tight control as well as pattern management.

Movement or some form of exercise can help to utilize insulin by reducing insulin resistance. Sometimes, a person who cannot control their blood sugar with diet alone will need medication, such as insulin to get their blood sugars to a healthy range.

Most cases of gestational diabetes resolve with delivery. But many experts recommend being tested for diabetes six months postpartum to assess status.

Latent Autoimmune Diabetes in Adults (LADA)

Latent autoimmune diabetes in adults, otherwise referred to LADA or diabetes 1.5 is very similar to type 1 diabetes with the exception that it usually occurs later in life. People with LADA have the presence of islet antibodies at diagnosis, but the progression of beta cell (β-cell) failure (when the cells of the pancreas stop making insulin) is slow.

Oftentimes people are mistakenly diagnosed with type 2 diabetes when they actually have LADA. LADA can also resemble type 1 diabetes due to beta cell dysfunction and testing will be done to distinguish between the two.

The prevalence of LADA is around 10% among incident case subjects of diabetes aged 40–75 years. Among people younger than 35 with type 2 diabetes, the frequency of LADA is higher.

At initial diagnosis, most people with LADA do not require insulin because their pancreas is still making some. However, within six years, β-cell function is severely impaired, leading to insulin dependency in most LADA patients.

Monogenic Diabetes

Monogenic diabetes is a rare form of diabetes and occurs when there are mutations or defects in one (mono) gene. According to the National Institute of Diabetes and Digestive and Kidney Disease (NIDDK), monogenic forms of diabetes account for about 1% to 4% of all cases of diabetes in the United States.

It appears in several forms and is most common in people 25 years and younger. It is characterized by a defect in beta cell function, the cells that make insulin. Therefore, the body is less able to make insulin but the cells are not necessarily resistant to it like in type 2 diabetes.

We are going to cover two forms of monogenic diabetes: Neonational diabetes (NDM) and maturity-onset diabetes of the young (MODY).

Neonatal Diabetes Mellitus (NDM)

Neonatal diabetes (NDM), also known as congenital diabetes is typically diagnosed in the first 6-to-12 months of life. It can either be transient or permanent. It occurs in approximately 1 in 90,000 to 160,000 live births and there are over 20 known genetic causes for neonatal diabetes mellitus.

Infants with NDM do not produce enough insulin, leading to an increase in blood glucose. NDM is often mistaken for type 1 diabetes, but type 1 diabetes is very rarely seen before 6 months of age.

In infants with hyperglycemia (high blood sugar) who are being treated with insulin, but still have persistent elevated blood sugars for more than one week, a neonatal diabetes diagnosis should be investigated as well as prompt genetic testing.

Signs and symptoms may include frequent urination, rapid breathing, or dehydration. Infants with NDM may also be smaller in size and have difficulty gaining weight and growing.

Sometimes treatment can be successful with oral glucose lowering medications called sulfanylureas; in this case early treatment may improve neurological outcomes. In addition, proper treatment can normalize growth and development.

Maturity-Onset Diabetes of the Young (MODY)

Maturity-onset diabetes of the young (MODY) accounts for about 2% of people with diabetes and is diagnosed during adolescence or early adulthood. A number of gene mutations have been known to cause MODY.

Sometimes people with MODY have no symptoms at all and may only have slightly elevated blood sugars that are recognized during routine blood work. Other types of gene mutations will cause higher blood sugar levels and require medical intervention by the form of insulin or oral diabetes medicines.

People with MODY typically have a family history of diabetes—you may see a parent, grandparent and child with it. Genetic testing is needed to diagnose MODY and other monogenic forms of diabetes. It is recommended to test for these forms of diabetes if:

  • Diabetes is diagnosed within the first 6 months of age
  • Diabetes is diagnosed in children and young adults, particularly those with a strong family history of diabetes, who do not have typical features of type 1 or type 2 diabetes, such as the presence of diabetes-related autoantibodies, obesity, and other metabolic features
  • A person has stable, mild fasting hyperglycemia, especially if obesity is not present

Diabetes Mellitus Symptoms

Although there are many forms of diabetes, most of the symptoms are the same. The pace in which they appear can be different. For example, in people with type 2 diabetes, symptoms often develop over several years and can go on for a long time without being noticed, sometimes not even at all. That's why it's important to know the risk factors for diabetes.

In opposition, people with type 1 diabetes can develop symptoms in just a few weeks or months and symptoms can be severe. In addition to the most common symptoms, people with type 1 diabetes, may also have stomach pain, nausea, fruity breath or a very serious acute consequence of elevated blood sugar, diabetic ketoacidosis.

The most common symptoms of elevated blood sugar include:

  • Polyuria: Excessive urination, often at night
  • Polydipsia: Excessive thirst or thirst that can not be quenched
  • Polyphagia: Excessive hunger which is often paired with weight loss
  • Weight loss
  • Numbness and tingling in the hands and feet
  • Feeling very tired or fatigued
  • Dry skin
  • Sores that heal slowly
  • Having more infections than usual

Another very rare symptom of very elevated blood sugar in people with type 2 diabetes is nonketotic hyperosmolar syndrome.

Complications

Most forms of diabetes are chronic therefore, proper management of blood sugars will be a critical part in preventing short and long term complications. When diabetes is not managed well for extended periods of time, it can lead to a variety of micro (small) and macro (large) vascular issues.

Neuropathy

Neuropathy is disease of the nervous system that is often characterized by numbness, tingling, and burning. The three major forms in people with diabetes are peripheral neuropathy, autonomic neuropathy, and mononeuropathy.

The most common form is peripheral neuropathy, which affects mainly the legs and feet. This can increase the risk of with risk of foot ulcers, amputations, and Charcot joints.

Autonomic neuropathy causing gastrointestinal (gastroparesis- nerve damage that affects the stomach), genitourinary, and cardiovascular symptoms and sexual dysfunction.

Other complications of diabetes mellitus include:

Causes and Risk Factors

The causes of diabetes will differ depending on the type of diabetes you have. For example, diabetes that affects the body's ability to make insulin, as in type 1 diabetes, has multiple genetic predispositions and is also related to environmental factors that are still poorly defined. People with this type of diabetes are rarely obese.

These types of diabetes are also associated with other autoimmune diseases, such as, such as Graves' disease, Hashimoto's thyroiditis, Addison's disease, vitiligo, celiac sprue, autoimmune hepatitis, myasthenia gravis, and pernicious anemia.

Type 2 diabetes is largely a disease related to lifestyle, however, it appears that people who have family members who have been diagnosed with type 2 diabetes are at a greater risk for developing it themselves.

In addition, people of African-American, Hispanic, Pacific-Island, or Native-American descent also have a higher-than-normal rate of type 2 diabetes. Studies show more than 120 gene variants have been identified as linked to causing type 2 diabetes. However, having a genetic disposition towards type 2 is not a guarantee of diagnosis.

Lifestyle plays an important part in determining who gets diabetes. Some potential causes include poor diet, sedentary lifestyle and low activity level, increase in age, elevated cholesterol or lipid levels, obesity, history of metabolic syndrome (characterized by high cholesterol and triglycerides, high waist-to-hip ratio, high blood pressure), and history of gestational diabetes.

Diagnosis

A diagnoses of diabetes usually involves a blood test. In most forms of diabetes, assessing a person hemoglobin A1C (a three month average of blood sugar), is a way to confirm a diagnosis.

This type of test is used more commonly to diagnose diabetes in individuals with risk factors and can also identify those with prediabetes, who are at higher risk of developing diabetes in the future.

However, not all types of diabetes are straightforward and therefore some people may need additional blood work, genetic testing, or an oral glucose tolerance test to confirm a diagnosis.

If your medical team is using another means to diagnose type 2 diabetes, such as a fasting plasma glucose or a random blood sugar test, they will need to confirm elevated levels on two separate occasions.

Treatment

All treatment plans for people with diabetes should be individualized. Consideration of a persons' past medical history, blood sugar control, culture, diet preferences, and goals, will be important in formulating a plan. Depending on the type of diabetes you have and your blood sugar status at diagnosis, your treatment plan will look different.

For example, a person diagnosed with prediabetes can start treatment with lifestyle changes—a small amount of weight loss, reducing intake of processed foods and simple sugars, exercise, and smoking cessation.

Whereas, someone with type 2 diabetes who has a very high hemoglobin A1c may need to start medication such as, oral glucose-lowering medication, an injectable medication such as a GLP-1 agonist, or a combination in addition to lifestyle changes.

Each individual's needs for diabetes treatment will be different, so try not to compare yourself to others.

People with type 1 diabetes or other immune-mediated types of diabetes will likely need to start insulin therapy via multiple daily injections or infusion. An endocrinologist, often referred to as a diabetes doctor, will be an important part of the treatment team, particularly for those people with type 1 diabetes.

People with prediabetes and type 2 diabetes can often receive treatment from their primary physician, but if their treatment plan appears to be too complicated, they can also benefit from seeing an endocrinologist.

In addition to lifestyle modifications (weight loss, healthy eating plan, exercise, smoking cessation), people with diabetes may need to see certain specialists. For example, people newly diagnosed with type 2 diabetes should receive a dilated eye exam and those diagnosed with type 1 diabetes, within 5 years of diagnosis and every year thereafter.

If you are experiencing issues with your lower extremities, such as numbness and tingling in your feet, you may need to see a podiatrist or a vascular doctor. If you have elevated cholesterol, type 2 diabetes, hypertension, and a family history of diabetes, you may need to see a cardiologist.

Management

Diabetes is a disease that needs to be managed daily. Blood sugar testing, carbohydrate counting, exercise, adherence to medication, and specialist appointments are just some of the things that people with diabetes need to manage.

Managing diabetes can become tiresome, confusing, and overwhelming, especially if a person is not thoroughly educated about their condition and treatment plan. The good news is that all people with diabetes can receive ongoing education and support.

The American Diabetes Association recommends that all people with diabetes receive diabetes self-management education (DSME) at the time of diagnosis and as needed thereafter.

Diabetes self-management education may lower the risk of diabetes complications as well as decrease costs. It does this by reducing or eliminating medications, emergency room visits and helping people access cost-savings programs.

In addition, DSME has been shown to reduce the onset and/or advancement of diabetes complications, to improve quality of life and lifestyle behaviors such as having a more healthful eating pattern and engaging in regular physical activity.

Certified Diabetes Care and Education Specialists (CDCES) deliver DSME and specialize in all things related to diabetes. They can be considered your "diabetes cheerleader," offering a wealth of resources, information, and support.

Research demonstrates that working with a diabetes educator can improve outcomes for people with diabetes and prediabetes. If you don't have a CDCES, it's a great idea to add them to your healthcare team.

A Word From Verywell

There are many forms of diabetes which require different types of care and treatment regimes. For those people who have a family history of heart disease or type 2 diabetes, it's important to modify your lifestyle in an effort to reduce your risk of developing diabetes and its complications.

Weight loss, a healthy diet, exercise, and smoking cessation will be important in preventing diabetes. If you suspect that you have diabetes and are experiencing symptoms, seeking medical attention is critical.

Treatment and management of diabetes will vary based on the type you have. However, all people with diabetes will benefit from diabetes self-management education provided by a diabetes care and education specialist. These specialists can help lessen the burden of this disease, providing support and education.

Although long-term complications are possible, people with diabetes can live a long healthy life by keeping their diabetes in good control.

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