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Diabetes: Symptoms, Causes, and Treatments

  • A condition in which the body either does not produce insulin or does not use it properly
  • Symptoms include increased thirst, urination, fatigue, blurred vision, and hunger
  • Treatments include an insulin pump, as well as diet and lifestyle changes
  • Involves Endocrinology

Diabetes: Symptoms, Causes, and Treatments


Diabetes is a common condition in America. More than 30 million Americans have the condition, meaning their bodies either do not produce insulin or do not use it properly. Insulin is a hormone made in the pancreas that helps the cells in the body absorb the glucose (sugar), which we use for energy.

"When a patient with diabetes comes to Yale Medicine, we work with them to develop optimal treatment options based on their lifestyle, their goals and their overall health,” says Ania Jastreboff, MD, PhD, an endocrinologist and director of the Yale Medicine Metabolic Health & Weight Loss Program.

“Rather than treating only the disease, we treat patients as whole people, helping them live healthier, happier, more fulfilling lives,” Dr. Jastreboff says.

Are there different types of diabetes?

Type 1 diabetes is often, but not always, diagnosed earlier in life. In this condition, the cells in the pancreas that make insulin are destroyed. This means that these patients—about 1 in 10 diabetics—must have a delivery system, such as injections or a pump, that delivers insulin continuously throughout the day.

Type 2 diabetes is more common, affecting 9 in 10 diabetics. “This condition is usually diagnosed in the setting of overweight or obesity,” says Dr. Jastreboff. In this form of the disease, the pancreas continues to produce insulin, but the cells become resistant to its effects. This leads to a diminished capacity to utilize glucose, which leads to a buildup of glucose in the blood.

Gestational diabetes can occur during pregnancy, especially if the woman is overweight or obese. This type may resolve after a woman gives birth, but she remains at a significantly increased risk of developing type 2 diabetes in the future.

What are the symptoms of diabetes?

People with the condition often have the following constellation of symptoms:

  • Increased thirst
  • Increased urination
  • Fatigue

They may also have:

  • Blurred vision
  • Increased hunger
  • Infections or sores that heal very slowly

In Type 1 diabetes, the symptoms mentioned above often come on rapidly and include significant weight loss.

“These individuals may be very ill, both from significant dehydration (from their bodies trying to rid themselves of excess sugar in the blood), as well as due to ketones (acid) in the blood,” says Dr. Jastreboff.

Symptoms of type 2 diabetes may appear more gradually over the course of months in children or years in adults. Most of the tests used to diagnose diabetes have levels that can indicate prediabetes, which may persist for some time before the condition worsens and progresses to type 2 diabetes.

How is diabetes diagnosed?

A physician can diagnose diabetes through different kinds of blood tests. These include:

  • A Hemoglobin A1C test (this may be called an A1c, HbA1c, or glycated hemoglobin test). Blood is drawn once but indicates your average blood sugar over the last three months.
  • A fasting plasma glucose test (FPG), which is measured after you have had nothing to eat or drink for at least eight hours.
  • An oral glucose tolerance test (OGTT) requires the patient to drink a specific amount of sugar and tests your blood sugar two hours after consumption.
  • A random plasma glucose (RPG) test is taken without any deliberate fasting or ingestion of glucose. It may indicate diabetes in conjunction with symptoms of diabetes.

How is diabetes treated?

“A person with type 1 diabetes has to take insulin in order to live a normal and healthy life,” says Dr. Jastreboff.

The hormone can be delivered through regular insulin injections throughout the day and includes a combination of long-acting insulin as well as short-acting insulin to cover meals and correct elevated blood sugar levels.

A patient may instead choose to use an insulin pump, a small electronic device that delivers a continuous infusion of insulin through a catheter the patient places under the skin and changes every 2 to 3 days.

“The pump delivers (basal) insulin throughout the day,” Dr. Jastreboff says. “Also, the patient inputs information into the pump throughout the day with regard to how much and what he or she will eat, so the pump can give him or her extra (bolus) insulin for the food when the patient eats.

In addition to using an insulin pump, some patients with type 1 diabetes use a continuous glucose monitor device. That both checks blood sugar intermittently throughout the day and measures sugar in the patient’s tissue continuously.

Patients who have milder or earlier cases of type 2 diabetes may manage the condition with dietary and lifestyle interventions, including physical activity. As the duration and severity of type 2 diabetes increases, medications are used—some in pill form and some injectable.

“These can sensitize you to using insulin better or they can help you secrete more insulin,” Dr. Jastreboff says. As the disease progresses, some diabetics also need to take insulin.

Some cases of type 2 diabetes can go into remission through weight loss with dietary and lifestyle intervention, anti-obesity medications, as well as endoscopic procedures and bariatric surgery for weight loss.

What makes Yale Medicine’s approach to diabetes unique?

“Yale Medicine is unique in that we treat the whole patient rather than treating their disease,” says Dr. Jastreboff.

For patients with obesity or type 2 diabetes, which may improve with weight loss, Yale Medicine is developing a comprehensive weight management program. It will include all available interventions clinically proven to help people lose weight, including dietary and lifestyle interventions, behavioral health support, anti-obesity medications, and procedures such as gastric balloon and bariatric surgery.

Visit the Yale Medicine Diabetes Content Center for more diabetes-related articles and videos.