Diabetes Types, Symptoms, Causes, and Treatments

Author: Disabled World (DW)
Updated/Revised Date: 2 Nov 2026

Table of Contents:
Synopsis - Definition - About This Section - FAQs - Publications - Subtopics

Synopsis

An in-depth guide to type 1, type 2, and gestational diabetes, covering symptoms, causes, complications, blood sugar testing, and treatment options for each type.

At a Glance

• 1 - Insulin cannot be taken as a pill because the stomach would break it down.
• 2 - Type 2 diabetes accounts for about 90 to 95 percent of all cases of diabetes.
• 3 - An A1c of 6.5 percent or higher indicates diabetes, and 5.7 to 6.4 percent indicates prediabetes.
• 4 - Losing 5 to 7 percent of body weight can improve glucose control in people with type 2 diabetes who are overweight.

Topic Definition

Diabetes Mellitus

Diabetes, known medically as diabetes mellitus, is a group of conditions in which the body cannot properly regulate the amount of glucose - a form of sugar the body uses for energy - in the blood. Normally the hormone insulin, produced by the pancreas, moves glucose out of the bloodstream and into muscle, fat, and liver cells so it can fuel daily activity. In people with diabetes, the body either fails to produce enough insulin or cannot use it effectively, so glucose builds up in the blood and gradually damages cells, tissues, and organs. The main forms include type 1 diabetes, an autoimmune condition that destroys insulin-producing beta cells; type 2 diabetes, driven largely by insulin resistance and the most common form; and gestational diabetes, which develops during pregnancy. Left uncontrolled, diabetes can lead to serious complications affecting the kidneys, nerves, eyes, and blood vessels.

Overview

Diabetes, known medically as diabetes mellitus, is a group of diseases in which the body cannot properly regulate the amount of sugar, called glucose, in the blood. Glucose is the body's main source of energy for everyday activities such as walking, working, and exercising. It comes mainly from the food people eat, and the liver also makes, stores, and releases glucose into the blood.

In people without diabetes, blood glucose is kept in a healthy range by several hormones, especially insulin, which is made by the pancreas. Insulin moves glucose out of the blood and into muscle, fat, and liver cells, where it is used for energy. In diabetes, the pancreas makes too little insulin, the body cannot use insulin properly, or both. Glucose then builds up in the blood, and over time high blood glucose damages blood vessels, nerves, and organs.

In the United States, about 40.1 million people, or 12.0 percent of the population, had diabetes in 2023, and about 11.0 million adults with diabetes did not know they had it [Centers for Disease Control and Prevention, 2026].

NOTE: To convert mmol/L to mg/dl or mg/dl to mmol/L visit our blood glucose conversion table.

Type 1 Diabetes

Type 1 diabetes is an autoimmune disease in which the immune system attacks and destroys the insulin-producing beta cells of the pancreas, so the body makes little or no insulin. The damage may build up over several years, but symptoms often appear quickly, sometimes over a few weeks. Type 1 diabetes is most often diagnosed in children, teens, and young adults, but it can begin at any age. About 2.1 million Americans have diagnosed type 1 diabetes, including about 314,000 children and teens younger than 20 [Centers for Disease Control and Prevention, 2026]. There is no known way to prevent it, and people with type 1 diabetes need insulin every day.

Type 2 Diabetes

Type 2 diabetes is the most common form, accounting for about 90 to 95 percent of all diabetes. It develops when muscle, fat, and liver cells do not respond well to insulin (insulin resistance) and the pancreas can no longer make enough extra insulin to make up for it. Symptoms usually develop slowly and may be mild, so many people have type 2 diabetes for years without knowing it. It is most common in middle-aged and older adults and in people who are overweight, but it is becoming more common in children and teens. The older names "non-insulin dependent" and "adult-onset" diabetes are no longer used, because younger people can have it and many people with type 2 diabetes need insulin.

Gestational Diabetes

Gestational diabetes is high blood glucose that first develops during pregnancy, usually around the middle of pregnancy. Pregnant women are commonly tested for it between 24 and 28 weeks. It raises the chance of having a larger baby and of complications at birth. It usually goes away after the baby is born, but women who have had it, and their children, are more likely to develop type 2 diabetes later in life.

Prediabetes and Metabolic Syndrome

Prediabetes means blood glucose is higher than normal but not yet high enough to be diagnosed as diabetes. About 115.2 million U.S. adults have prediabetes, including more than half of people aged 65 or older, and most of them do not know it [Centers for Disease Control and Prevention, 2026]. Losing a modest amount of weight and getting regular physical activity can prevent or delay type 2 diabetes in many people with prediabetes.

Metabolic Syndrome, also called Syndrome X, is a cluster of conditions that occur together and raise the risk of type 2 diabetes, heart disease, and stroke: high blood glucose, high triglycerides, high blood pressure, low HDL cholesterol, and excess fat around the waist.

Symptoms of Diabetes

Symptoms of type 1 diabetes often come on suddenly and can be severe, while symptoms of type 2 diabetes may be subtle or absent for years. Common symptoms include:

• Increased thirst (polydipsia) and frequent urination (polyuria), as the kidneys try to remove extra glucose
• Increased hunger (polyphagia)
• Unexplained weight loss, especially in type 1 diabetes
• Fatigue and weakness
• Blurry vision
• Slow-healing cuts and sores
• Frequent infections, such as skin, urinary tract, and yeast infections
• Numbness or tingling in the hands or feet

Confusion, extreme drowsiness, vomiting, or rapid breathing in a person with diabetes can be signs of a medical emergency and need immediate care.

Causes and Risk Factors

Type 1 diabetes is caused by an autoimmune reaction. Genes play a part, and some viral infections may help trigger it. It is most common in people of non-Hispanic white, Northern European background.

Type 2 diabetes has strong genetic links and tends to run in families, but lifestyle plays a large role. Risk factors include being overweight, physical inactivity, being 45 or older, having a parent or sibling with type 2 diabetes, having had gestational diabetes, having prediabetes, high blood pressure, and high triglycerides. African Americans, American Indians and Alaska Natives, Hispanic and Latino Americans, Asian Americans, and Pacific Islanders are at higher risk. Men are slightly more likely than women to develop diabetes.

Testing and Diagnosis

A health care provider diagnoses diabetes with blood tests, usually repeated on another day to confirm the result [MedlinePlus, n.d.]:

• Fasting plasma glucose: after at least 8 hours without food, a level of 126 mg/dl (7.0 mmol/L) or higher indicates diabetes, and 100 to 125 mg/dl indicates prediabetes.
• A1c (glycated hemoglobin): shows the average blood glucose over the past two to three months. A result of 6.5 percent or higher indicates diabetes, and 5.7 to 6.4 percent indicates prediabetes.
• Oral glucose tolerance test: blood glucose is measured two hours after drinking a sweet drink with 75 grams of glucose. A level of 200 mg/dl or higher indicates diabetes, and 140 to 199 mg/dl indicates prediabetes.
• Random plasma glucose: a level of 200 mg/dl or higher in a person with classic symptoms indicates diabetes.

People with diabetes check their own glucose with a finger-stick meter or a continuous glucose monitor (CGM), a small sensor worn on the skin that reads glucose every few minutes. Home meters are less precise than laboratory tests; under U.S. Food and Drug Administration (FDA) standards, most readings must fall within 15 percent of laboratory values. Many adults with diabetes aim for an A1c below 7 percent and a before-meal glucose of about 80 to 130 mg/dl, but goals are set individually with a health care provider.

Complications of Diabetes

Over time, high blood glucose (Hyperglycemia) damages blood vessels and nerves throughout the body. Diabetes is a leading cause of kidney failure (diabetic nephropathy), blindness in working-age adults (diabetic retinopathy), and lower-limb amputation. Nerve damage (diabetic neuropathy) can cause numbness, pain, foot ulcers, digestive problems such as gastroparesis, and dizziness when standing up. Diabetes also speeds the buildup of fatty plaque in the arteries, which raises the risk of heart attack, stroke, and peripheral artery disease, and it makes infections harder to fight.

Short-term emergencies can also occur:

• Hypoglycemia (low blood glucose) can happen when a person taking insulin or certain other medicines skips a meal, exercises more than usual, takes too much medicine, or drinks alcohol. Signs include shaking, sweating, fast heartbeat, dizziness, hunger, and confusion, and severe hypoglycemia can cause seizures or loss of consciousness.
• Diabetic ketoacidosis (DKA) is a dangerous buildup of acids called ketones when the body has too little insulin. It is most common in type 1 diabetes and can be triggered by illness, infection, missed insulin, or stress.
• Hyperosmolar hyperglycemic state is extremely high blood glucose with severe dehydration, most often in older adults with type 2 diabetes who are ill or dehydrated.

Regular Checkups

People with diabetes should have a dilated eye exam at least once a year, yearly urine and blood tests to check the kidneys, regular foot checks for loss of feeling, sores, and poor circulation, and regular checks of blood pressure and cholesterol, which also affect the risk of heart disease.

Managing Diabetes Day to Day

• Healthy eating: A balanced eating plan with plenty of vegetables, whole grains, and fiber, and limited added sugars, refined starches, and saturated fat, helps keep glucose steady. A dietitian or diabetes educator can help with meal planning and carbohydrate counting.
• Physical activity: Adults are generally advised to aim for at least 150 minutes of moderate activity, such as brisk walking, each week, and any regular activity helps. People with complications should ask their provider which activities are safe.
• Weight: For people with type 2 diabetes who are overweight, losing even 5 to 7 percent of body weight can improve glucose control.
• Alcohol: People with diabetes who drink should keep to the limits their provider advises and avoid drinking on an empty stomach, which can cause low blood glucose. One standard drink in the United States is 1.5 ounces (44 ml) of liquor, 12 ounces (355 ml) of beer, or 5 ounces (148 ml) of wine.
• Smoking: Smoking raises the risk of almost every complication of diabetes, and quitting is one of the most helpful steps a person can take.
• Monitoring: Keeping a record of glucose readings, medicines, meals, and activity helps people and their care team adjust treatment.

Medical Treatment

Treatment is planned with a care team that may include a primary care provider, an endocrinologist, a diabetes educator, a dietitian, and eye and foot specialists. Education about self-care is an essential part of treatment for every type of diabetes.

People with type 1 diabetes need insulin every day, usually as a long-acting insulin plus a rapid-acting insulin at meals, given by injection or by an insulin pump. Insulin cannot be taken as a pill, because it would be broken down in the stomach. Many people now use a continuous glucose monitor, and some use automated insulin delivery systems that adjust insulin based on CGM readings. Because insulin lowers blood glucose whether or not a person has eaten, people taking insulin need to match their doses to their meals and activity.

For type 2 diabetes, healthy eating, physical activity, and weight loss are the foundation of treatment. Metformin is usually the first medicine. Newer medicines, including GLP-1 receptor agonists such as semaglutide and dual GIP and GLP-1 agonists such as tirzepatide, and SGLT2 inhibitors such as empagliflozin, lower blood glucose and can also aid weight loss or protect the heart and kidneys. Many people need more than one medicine, and some eventually need insulin.

Outlook

Diabetes was the seventh leading cause of death in the United States in 2024, with 94,445 deaths [Centers for Disease Control and Prevention, n.d.], and heart disease is the most common cause of death in people with diabetes. Outlook depends on the type of diabetes, how well blood glucose, blood pressure, and cholesterol are controlled, and whether complications develop. Good control has been proven to slow or prevent complications. Survival has improved greatly: in the Pittsburgh Epidemiology of Diabetes Complications study, people diagnosed with type 1 diabetes between 1965 and 1980 had a life expectancy of about 69 years, only about four years less than the general U.S. population at that time, a far smaller gap than for those diagnosed earlier [Miller et al., 2012].

Diabetes in America: Key Statistics

• In 2023, 40.1 million Americans, or 12.0% of the population, had diabetes.
• About 29.1 million people had been diagnosed, and about 11.0 million adults, or 27.6% of adults with diabetes, were undiagnosed.
• About 2.1 million Americans have diagnosed type 1 diabetes, including 314,000 children and adolescents younger than 20.
• About 115.2 million U.S. adults have prediabetes, including 31.3 million people aged 65 or older (52.1% of that age group).
• Diabetes was the 7th leading cause of death in the United States in 2024, with 94,445 deaths.

Frequently Asked Questions

What is a normal blood sugar range for someone without diabetes?

A fasting blood glucose level below 100 mg/dl is generally considered normal, while a fasting level of 126 mg/dl or higher on repeat testing usually indicates diabetes.

Can type 2 diabetes be reversed?

Type 2 diabetes cannot always be fully reversed, but many people can achieve normal blood sugar levels and reduce or stop medication through sustained weight loss, healthy eating, and regular exercise.

What is the difference between type 1 and type 2 diabetes?

Type 1 diabetes is an autoimmune condition in which the body produces little or no insulin, while type 2 diabetes involves insulin resistance and reduced insulin production, often linked to lifestyle and genetics.

Is diabetes hereditary?

Diabetes can run in families, and type 2 diabetes in particular has strong genetic links, though lifestyle factors such as diet, weight, and activity level also play a major role.

What should a person do if their blood sugar drops too low?

A person with low blood sugar should quickly consume fast-acting carbohydrates such as juice or glucose tablets, then recheck their level, and seek medical help if symptoms are severe or do not improve.

Can people with diabetes eat sugar?

People with diabetes can eat some sugar in moderation as part of a balanced diet, but they need to monitor total carbohydrate intake and work with a health care provider or dietitian to manage blood sugar.

How often should a person with diabetes see a doctor?

A person with diabetes typically needs checkups every three to six months for blood sugar monitoring, along with yearly eye exams and regular screening for kidney, nerve, and cardiovascular complications.

What is prediabetes?

Prediabetes means blood sugar is higher than normal but not yet high enough for a diabetes diagnosis, often shown by an A1c of 5.7 to 6.4 percent. Losing a small amount of weight and staying active can greatly lower the chance of it turning into type 2 diabetes.

Further Resources

• Blood Sugar Levels Including Printable Chart - Thomas C. Weiss - (2014-03-27)
• Blood Glucose mmol/L to mg/dl Conversion Chart - Disabled World - (2018-07-03)
• Low Glycemic Index Foods for Breakfast to Control Daily Blood Sugar - Institute of Food Science and Technology - (2012-04-04)

References

• Centers for Disease Control and Prevention. (2026). National diabetes statistics report.
• Centers for Disease Control and Prevention. (n.d.). FastStats: Leading causes of death. National Center for Health Statistics.
• MedlinePlus. (n.d.). Diabetes. National Library of Medicine.
• Miller, R. G., Secrest, A. M., Sharma, R. K., Songer, T. J., and Orchard, T. J. (2012). Improvements in the life expectancy of type 1 diabetes: The Pittsburgh Epidemiology of Diabetes Complications study cohort. Diabetes, 61(11), 2987 - 2992.

Curated and edited by Ian C. Langtree, Founder and Editor-in-Chief, Disabled World. This section is maintained by the Disabled World editorial team. Last updated: 2 Nov 2026