Types of Diabetes Mellitus

Diabetes mellitus is a chronic disease marked by an excess of blood glucose (blood sugar). There are five types of diabetes mellitus: type 1 diabetes, type 2 diabetes, gestational diabetes, monogenic diabetes (MODY), and latent autoimmune diabetes in adults (LADA). However, researchers are now even considering a fifth type, as Alzheimer's is often referred to as type 3 diabetes due to a strong link between blood sugar and brain health. These diseases may be related to lifestyle or to genetic causes, and they may affect people at different life stages.


There are several similarities between the five types of diabetes. For example, all five types involve alterations in insulin and glucose metabolism. Glucose is a component of carbohydrates and serves as the body's main energy source. It circulates in the bloodstream until insulin, a hormone produced by the pancreas, helps it get into the body cells where it is used for fuel to create energy. Insulin is essential in helping the body store and use glucose, but its function or production may be compromised depending on the type of diabetes.

Blood glucose levels rise when there is not enough insulin (as in type 1 diabetes and LADA), or when the body doesn't respond to insulin as it should (as in type 2 diabetes and gestational diabetes).

In terms of shared symptoms, type 1, type 2, gestational diabetes, and LADA (often considered type 1.5 diabetes) can all produce several short-term complications, including symptoms of fatigue, extreme thirst, and increased urinary frequency.

They can also result in more serious long-term complications, including vision changes and an increased risk of heart disease and stroke. Gestational diabetes may cause complications during pregnancy and delivery. Medical management is available for all of these types of diabetes mellitus, which reduces the symptoms and the risk of complications.

Diabetes mellitus is different from the less common diabetes insipidus (DI), which is a rare kidney problem characterized by frequent urination and excessive thirst. While it is also called diabetes, DI does not cause blood sugar problems.

Types of Diabetes Mellitus

All five types of diabetes mellitus are fairly common. If you experience urinary frequency, increased thirst, episodes of lightheadedness, or unexplained weight changes, you should seek medical attention, as these could be symptoms of diabetes or another metabolic problem.

Early diagnosis is important to prevent complications. Diabetes mellitus is usually characterized by elevated blood glucose and the presence of excess glucose in the urine. Treatment depends on the specific type of diabetes mellitus you have.

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. Symptoms may range from subtle to extreme. Before diagnosis, children may wet the bed, often feel very sleepy, and may have impaired growth and learning. In some instances, children develop 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 increase of type 1 diabetes among family members, which suggests that there may be a hereditary component to the condition. It is also now 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. Treatment approaches may also include regular exercise and eating a balanced diet rich in whole grains, lean meat, nuts and beans, and plenty of fruits and vegetables.

Type 1.5 Diabetes

Latent Autoimmune Diabetes in Adults (LADA) is very similar to type 1 diabetes, except for the fact that it strikes later in life. LADA usually sets in around age 30, whereas type 1 often sets in around childhood or adolescence. In fact, LADA is often misdiagnosed as type 2 diabetes at first, until further inspection reveals that the symptoms are tied to low or no insulin production.

Because LADA is an autoimmune condition, 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 develop the disease thanks to a family history of autoimmune conditions or a genetic predisposition to type 1 or type 2 diabetes.

Treatment for LADA usually involves supporting the body's existing insulin production for as long as it lasts, then transitioning to taking regular insulin infusions as needed. Like type 1 diabetes, LADA is a lifelong condition that can be managed with insulin and other medications, in addition to 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 well-managed.

Type 2 diabetes is often preceded by a condition described as pre-diabetes or a condition called metabolic syndrome. There is a great deal of overlap between these conditions, and they are both characterized by elevated blood sugar, high blood pressure, high cholesterol, and a high body mass index (BMI) or obesity.

Often, weight and diet management can reverse pre-diabetes or metabolic syndrome and can prevent the development of type 2 diabetes.

Type 2 diabetes is treated with medication meant to improve the glucose uptake into the cell 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. Work with your doctor and a certified diabetes educator to talk about a treatment plan that's right for you.

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 and can 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, and if the pancreas can't keep up with insulin production, you may end up with consistently elevated blood sugar. Gestational diabetes may also develop if you are more genetically susceptible; if you are overweight; or simply because sometimes insulin resistance may increase during pregnancy.

After the baby is born, many women see their blood sugar return to normal. However, having gestational diabetes does make some women at higher risk to develop type 2 diabetes down the line, so it is important that you regularly have your blood sugar checked at your yearly doctor appointments if you have or have had gestational diabetes.

Treatment for gestational diabetes is usually lifestyle changes, as many medications may have unwanted side effects for both mother and baby during the 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.

Type 3 Diabetes

The American Diabetes Association recently released a statement suggesting that having diabetes or prediabetes is the second biggest risk factor for the onset of Alzheimer's disease, a type of progressive dementia currently affecting more than 5 million Americans.

Research centering on the link specifically between type 2 diabetes and Alzheimer's has led many experts to consider 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.

Current statistics suggest that having diabetes can increase your risk of Alzheimer's by 65 percent and that 50 percent of the population 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 the decline and even improve function.

If you have type 2 diabetes, talk to your primary care provider for more info about the link between Alzheimer's and diabetes.

A Word From Verywell

Diabetes mellitus is a relatively common chronic condition. While it can be well-managed to prevent complications, each type of diabetes mellitus requires close and consistent medical attention to prevent more serious developments.

Seek out a supportive healthcare team that incorporates not only medicine and regular blood testing but also holistic treatments such as diet, exercise, and stress management, all of which have been proven to be effective in treating each type of the disease.

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  1. Kandimalla R, Thirumala V, Reddy PH. Is Alzheimer's disease a Type 3 Diabetes? A critical appraisal. Biochim Biophys Acta Mol Basis Dis. 2017;1863(5):1078-1089.


  2. Carbohydrates. US National Library of Medicine. October 2019.

  3. Gestational Diabetes and Pregnancy. Centers for Disease Control and Prevention. October 2019.

  4. DeBruyne LK, Pinna K. Nutrition For Health And Health Care (Fifth Edition). Cengage Learning. 2013.

  5. Type 1 Diabetes. National Institute of Diabetes and Digestive and Kidney Diseases. July 2017.

  6. Laugesen E, Østergaard JA, Leslie RD. Latent autoimmune diabetes of the adult: current knowledge and uncertainty. Diabet Med. 2015;32(7):843-52.  doi:10.1111/dme.12700

  7. Martín-timón I, Sevillano-collantes C, Segura-galindo A, Del cañizo-gómez FJ. Type 2 diabetes and cardiovascular disease: Have all risk factors the same strength?. World J Diabetes. 2014;5(4):444-70.  doi:10.4239/wjd.v5.i4.444

  8. Gestational diabetes diet. Centers for Disease Control and Prevention. March 2019.

  9. Cholerton B, Baker LD, Montine TJ, Craft S. Type 2 Diabetes, Cognition, and Dementia in Older Adults: Toward a Precision Health Approach. Diabetes Spectr. 2016;29(4):210-219.  doi:10.2337/ds16-0041

  10. Li X, Song D, Leng SX. Link between type 2 diabetes and Alzheimer's disease: from epidemiology to mechanism and treatment. Clin Interv Aging. 2015;10:549-60.  doi:10.2147/CIA.S74042

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