Types of Diabetes Mellitus

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Diabetes mellitus is a chronic disease marked by abnormally high levels of glucose—sugar derived from carbohydrates that serves as the body's main source of energy—in the blood.

There are five types of diabetes: type 1 diabetes, type 2 diabetes, latent autoimmune diabetes in adults (LADA), gestational diabetes, and monogenic diabetes. Some experts also regard Alzheimer's disease as a type of diabetes, calling it type 3.

Some forms of diabetes are genetic in origin, while others are related to lifestyle or other factors. Regardless, the disease requires lifelong management in order to avoid serious, or even life-threatening, complications.

What They Have in Common

All types of diabetes are characterized by changes in the function of insulin, a hormone produced by the pancreas that helps to move glucose from the blood into cells, where it's used for fuel.

Depending on the type of diabetes, either the pancreas does not produce insulin or the body is unable to use it as it should. Either way, without ample insulin or a healthy response to it, the sugar circulating in the blood cannot get into cells.

Early symptoms of diabetes, whatever the type, include fatigue, extreme thirst, and frequent urination.

If the disease progresses, a number of complications are possible, including vision changes or loss (diabetic retinopathy), diabetic neuropathy (nerve damage), increased risk of heart disease, kidney damage, and more.

Glucose Level Blood Test
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Type 1 Diabetes

Type 1 diabetes occurs when the pancreas stops or nearly stops producing insulin. Type 1 diabetes has also been referred to as insulin-dependent diabetes and juvenile diabetes.

Type 1 diabetes usually develops during childhood, most often between the ages of 4 and 14. Symptoms tend to develop quickly and may range from subtle to extreme.

Before diagnosis, children may wet the bed, feel very sleepy often, and/or have impaired growth and learning. Some children have seizures or loss of consciousness due to an extreme rise in blood sugar.

It is not completely clear what causes type 1 diabetes. There is an increased risk of type 1 diabetes among family members, which suggests that there may be a hereditary component to the condition. It is also considered an autoimmune disease, as the body is fighting its own pancreatic cells. In some instances, type 1 diabetes may be triggered by a virus.

People with type 1 diabetes must take daily insulin replacement, either by injection or via an insulin pump. Ideally, blood glucose should be measured continuously through an automated monitor, and the insulin dose needs to be adjusted based on the blood glucose level and the food intake at each meal, as well as other factors such as physical activity and sleep.

Management approaches may also include regular exercise and eating a balanced diet rich in whole grains, lean meat, nuts, beans, and plenty of fruits and vegetables.

Latent Autoimmune Diabetes in Adults (LADA)

Like type 1 diabetes, LADA is an autoimmune disease. Also known as type 1.5 diabetes, LADA most often sets in around age 30. For that reason, it is sometimes initially misdiagnosed as type 2 diabetes. One telltale difference between the two is that LADA is not associated with weight gain.

With LADA, the body attacks the beta cells of the pancreas that produce insulin, severely limiting the body's insulin production over time. This may happen quickly or be drawn out over a longer period of time.

People affected by LADA may have a family history of autoimmune conditions or a genetic predisposition to type 1 or type 2 diabetes.

Treatment for LADA involves supporting the body's existing insulin production for as long as it lasts, then transitioning to regular insulin, other medications (if necessary), and a healthy diet and regular physical activity.

Type 2 Diabetes

Type 2 diabetes occurs when the body is unable to make effective use of insulin. This is often referred to as insulin resistance. Type 2 diabetes has also been called non-insulin dependent diabetes.

Some people may experience fatigue or increased urination as initial symptoms, but many people who have type 2 diabetes do not have any symptoms at all in the early stages. Later, complications such as vascular disease, heart attack, and stroke may develop if the disease is not under control.

Type 2 diabetes is often preceded by a condition described as prediabetes or another condition called metabolic syndrome. There is a great deal of overlap between these conditions. Both are characterized by elevated blood sugar, high blood pressure, high cholesterol, and obesity.

Often, weight and diet management can reverse prediabetes or metabolic syndrome so that type 2 diabetes can be prevented.

Type 2 diabetes is treated with medication meant to improve the glucose uptake into cells or increase the body's sensitivity to insulin, but great results have been seen by using diet and lifestyle changes, such as weight loss, exercise, and stress reduction to counteract the condition. Insulin may be needed later in the course of the condition.

Gestational Diabetes

If you develop high fasting blood sugar during pregnancy, but have not been diagnosed with diabetes previously, you may have gestational diabetes.

This condition can predispose your baby to growth and developmental issues, as well as complicate pregnancy and delivery. Regular monitoring of your blood sugar, your weight, and your baby's growth during pregnancy are necessary to minimize complications.

During pregnancy, placental hormones cause glucose levels to increase. If the pancreas can't keep up with that production, you may end up with consistently elevated blood sugar. Gestational diabetes may develop if you are genetically susceptible, if you are overweight, or simply because sometimes insulin resistance may increase during pregnancy.

The American Diabetes Association (ADA) advises that women who are planning a pregnancy get screened for diabetes if they have risk factors for the condition. It also recommends testing all women planning a pregnancy for undiagnosed diabetes.

Further, the ADA advises testing pregnant women before 15 weeks gestation if they have risk factors and recommends testing for undiagnosed diabetes at the first prenatal visit, if they have not been screened preconception.

After the baby is born, many women see their blood sugar return to normal. However, having gestational diabetes does put some women at higher risk for developing type 2 diabetes down the line. It's important that you have your blood sugar checked at your yearly doctor's appointments if you have or have had gestational diabetes.

Treatment for gestational diabetes begins with lifestyle changes, as many medications may have unwanted side effects for both mother and baby during pregnancy. Reducing your refined carb intake and increasing your activity level (especially with low-intensity, weight-bearing exercises such as walking and yoga) can help balance your glucose levels.

Monogenic Diabetes

Monogenic diabetes is a lesser known type of diabetes because it's rare, making up only about 1% to 4% of diabetes cases.

This form is caused by specific, known gene mutations that usually reduce the body's ability to make insulin. Sometimes these are inherited from parents, and sometimes they're spontaneous.

There are two forms of monogenic diabetes:

  • Neonatal diabetes mellitus (NDM), which appears in the first six to 12 months of life
  • Maturity-onset diabetes of the young (MODY), which is diagnosed in later childhood or the teen years

Both forms may be misdiagnosed as type 1 diabetes, and MODY may be confused with type 2 diabetes.

These conditions can be diagnosed with genetic testing, which would be ordered if risk factors like a family history of diabetes or early onset are present. An accurate diagnosis is important so that children with monogenic diabetes get the right treatment.

Infants with NDM might need insulin or other medications temporarily or for life. MODY treatments can vary, depending on how severe a person's diabetes is.

Type 3 Diabetes

Many studies have suggested that having diabetes or prediabetes is a risk factor for the onset of Alzheimer's disease, a type of progressive dementia affecting more than 6 million Americans age 65 or older.

Research centering on the link specifically between type 2 diabetes and Alzheimer's has led some experts to call Alzheimer's disease type 3 diabetes. The connection seems to be that the characteristic amyloid plaques that form on the brain in Alzheimer's are tied to the effects of insulin resistance that seem to be localized to the brain.

Some research suggests that having diabetes can increase your risk of Alzheimer's by 65% and that 50% of people with type 2 diabetes will go on to develop Alzheimer's.

While direct causes are still being studied, there is a strong correlation between long-term blood sugar imbalance and inflammation in the brain, which may severely impact cognitive function.

Thankfully, common medications generally used as a first-line defense for type 2 diabetes also seem to reduce the impact on the brain and may help slow decline and even improve function.

If you have type 2 diabetes, be sure to talk with your healthcare provider about this link and any other risk factors you may have for Alzheimer's disease.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Gary Gilles
Gary Gilles is a licensed clinical professional counselor (LCPC) who has written about type 1 diabetes and served as a diabetes counselor. He began writing about diabetes after his son's diagnosis as an infant.