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What Is Type 1 Diabetes?

Causes, symptoms, diagnosis, treatments, and support

With Ilana Halperin MD and Elena Christofides MD

Learning you or your child has type 1 diabetes means taking an active role in health 24/7. Luckily, there are more low-key ways to track blood sugar and administer insulin than ever. From glucose monitoring to meal planning, we’re here to empower you with clear answers to all your pressing questions. 

Definition Symptoms | Diagnosis | Treatments | Complications 
Fast Facts | Frequently Asked Questions | Support 

What is type 1 diabetes?

Type 1 diabetes, sometimes called juvenile diabetes or type 1 diabetes mellitus, is a chronic autoimmune condition where your pancreas produces little or no insulin, the crucial hormone that helps convert the glucose in your bloodstream into fuel.

After digesting a meal, our bodies take the carbohydrates from our food and convert them into glucose, which travels through our bloodstream into our cells. Our cells then use this glucose as fuel to power everything they do.

Insulin works like a key for the glucose, unlocking the cells so that the glucose can enter. Without insulin, our cells can’t function, because the glucose remains locked out. As a result, glucose from food accumulates in the bloodstream. Too much accumulated glucose leads to a rise in blood sugar, which then causes symptoms to develop.

Type 1 Diabetes Fast FactsInfographic by Lauren Hunter

How common is type 1 diabetes?

Well, it’s a lot less common than type 2. According to the American Diabetes Association, 1.6 million Americans have type 1 diabetes, including 187,000 children and adolescents. Type 1 diabetes makes up between 5 and 10% of total diabetes cases in the United States, while type 2 diabetes covers the other 90 to 95%.

Type 1 diabetes is usually diagnosed before the age of 40, although occasionally people have been diagnosed later after an illness causes an immune response that triggers it. In the US, most type 1 diabetes diagnoses occur in children between the ages of 4 and 14 years old.

What’s the difference between type 1 and type 2 diabetes?

Think of insulin as a key that unlocks your cells, says Ilana Halperin MD, assistant professor of medicine at the University of Toronto. In type 1 diabetes, there is simply no key. “There is a total absence of insulin coming from the cells in the pancreas,” she says. Essentially, the body destroys the cells in the pancreas that are responsible for making insulin.

In type 2 diabetes, you have a rusty key that can’t open the lock as well. In this form, a person develops an insulin resistance, so that insulin doesn't perform correctly in their body.

Is type 1 diabetes genetic?

If one family member has type 1 diabetes, other relatives have an increased chance of developing the condition. One study of more than 1,400 children with type 1 diabetes showed that 12% had a first-degree relative who also had type 1—in other words, a parent or sibling.

The same study also showed that children with type 1 diabetes had a slightly higher chance of having a father diagnosed with type 1 rather than a mother, brother, or sister. In some cases, family members of people with type 1 diabetes also have a history of autoimmune conditions such as celiac disease or lupus.

Type 2 diabetes is caused by lifestyle and other factors, while type 1 is either genetic or acquired after the onset of an illness.

What causes type 1 diabetes?

Type 1 diabetes causes can be any kind of illness, including the common cold. That said, here are the most common causes:

  • Viral infectionResearchers believe that type 1 diabetes can be triggered by a virus, such as the common flu or cold. Frequently, type 1 diabetes comes on in the weeks following a viral infection, such as mumps, rubella, cytomegalovirus, measles, influenza, encephalitis, polio, or Epstein-Barr.
  • Injury to or removal of the pancreas. Very rarely, type 1 diabetes can be triggered by an injury or trauma to the pancreas. Whenever the pancreas is surgically removed, the body also loses the ability to produce insulin, which then causes type 

Causes of Type 1 Diabetes: viral infection & pancreas injuryThese are some common causes of Type 1 Diabetes.

Is type 1 diabetes an autoimmune disease?

When type 1 diabetes is triggered by a virus, someone predisposed to autoimmune conditions may develop an autoimmune response. This means that their body’s immune system will start attacking its own cells. In type 1 diabetes, the body attacks the beta cells in the pancreas that are responsible for producing insulin.

What are the signs and symptoms of type 1 diabetes?

“The most common symptoms of type 1 diabetes are excessive thirst, increased urination, and losing weight without trying,” says diabetes and metabolism specialist Elena Christofides MD, though unexplained weight loss is more common with type 1 diabetes in children than adults.

Type 1 Diabetes Infographic: statistics on diabetes cases

Common symptoms of untreated type 1 diabetes

  • Excessive thirst
  • Increased urination
  • Unexplained weight loss
  • Headache
  • Dehydration
  • Irritability
  • Mood swings
  • Increased appetite
  • Fatigue
  • Disruption of menstrual cycles and miscarriage (in adults)
  • Yeast infections
  • Waking up in the middle of the night to urinate

More severe symptoms of untreated type 1 diabetes

  • Nausea
  • Diarrhea
  • Vomiting

When type 1 diabetes goes untreated, it can lead to organ failure, coma, and even death. This happens because the body can no longer turn glucose into fuel, and it starts burning fat, which then produces ketones in the blood and urine.

A small amount of ketones aren't dangerous and can usually be detected if a person has been fasting or is on a low-carbohydrate diet. But too many ketones can actually change the blood’s acidity and result in a life-threatening condition called diabetic ketoacidosis.

Signs and symptoms of Type 1 diabetes: weight loss, frequent urination, irritability, blurry vision, fruity breathIf you have one or more of these symptoms contact your doctor.

Symptoms of type1 diabetes tend to look different in children than adults, according to Dr. Christofides.

Additional symptoms of type 1 diabetes in babies and toddlers

  • Weight loss
  • Failure to thrive, a condition involving weight loss or inability to gain weight combined with stunted growth
  • Colic or fussiness that just won’t let up
  • Poor-quality sleep that doesn’t improve no matter what you try
  • Bedwetting, especially after successful potty-training

All of these symptoms are a result of hyperglycemia—too much glucose circulating in our bloodstream, also known as high blood sugar. Any person experiencing hyperglycemia, particularly after a viral illness, should seek immediate medical help.

How is type 1 diabetes diagnosed?

Because the symptoms can develop rapidly, a diagnosis of type 1 diabetes is usually made by a pediatrician or a physician in the emergency room. Pediatricians might check a child’s glucose levels if there is unexplained weight loss or sudden bedwetting. Glucose tests are also commonly run when a person with type 1 diabetes symptoms arrives at the hospital.

Doctors can also diagnose type 1 diabetes by running several tests to check blood-sugar levels. The primary screening test for type 1 diabetes is the random blood-sugar test, which tells physicians the amount of glucose circulating in a person’s blood at a specific moment in time. A blood-sugar level of 200 milligrams per deciliter suggests diabetes.

The secondary test is a glycated hemoglobin test, or A1C test. This test measures the average amount of glucose in a person’s bloodstream over the past 90 days as a percentage.

A normal A1C level is between 5 and 5.5%, while anything higher than 5.7% indicates diabetes. When diabetes is controlled, a person’s A1C levels will be low.

“It’s a useful test because you don’t want to overreact,” says Dr. Christofides. “If someone has hyperglycemia for a week or a couple days, their A1C isn’t going to rise. This gives us a good reflection of what the glucose level was for the past three months.”

4 ways to manage diabetes: take insulin, exercise, eat a balanced diet and check your blood sugar

What are the treatments for type 1 diabetes?

Type 1 diabetes must be treated with insulin. To do this, a person with type 1 diabetes must inject insulin under their skin where it can be absorbed into their bloodstream to help glucose access the cells that require it. Insulin can’t be taken in pill form because the digestive juices in the stomach would destroy the insulin before it could work.

Treating T1D is all about the amount (dose) and timing of insulin, as well as the best way to get the right dose of this essential hormone to assure that the glucose circulating in your blood is able to be properly absorbed by your body. Having too much glucose (hyperglycemia) in your body can cause serious complications as can having too little glucose in your blood (hypoglycemia)

Insulin can be delivered by:

  • A pump
  • A pen
  • Injections with a syringe

All of these methods deliver insulin subcutaneously—usually in the fatty area of the abdomen—but each has different advantages and drawbacks. Someone using a syringe to inject insulin might prefer the ease that comes with a quick draw and delivery, rather than learning how to use a pump, which can be cumbersome, expensive, and sometimes confusing to learn (at least at first).

A pump, on the other hand, only requires a catheter and needle to be implanted every few days, meaning less jabs and work for needle-adverse users. Because insulin is stored in the pump, anyone who needs a dose can simply press a few buttons to have it delivered. Insulin pumps can also be programmed to deliver different doses throughout the day, or to make minor adjustments before mealtimes.

A pen is similar to a syringe injection except that the insulin is prefilled in cartridges, so users only need to load an insulin cartridge into the pen and administer it when needed, no measuring required. In addition to insulin, other medications, such as metformin, are also used to help reduce risk and manage type 1 diabetes.

Where can I get support?

“There’s no other disease where the management is so much in the hands of the patient,” says Dr. Halperin. “You can’t just get a prescription and take a pill once a day. It involves a lot of hard work on behalf of the person with diabetes and their family.” Because of this, a support system is crucial. After your internist and endocrinologist, here additional resources for help:

Support groups and nonprofits for type 1 diabetes


Formerly known as the Juvenile Diabetes Research Foundation, JDRF is a nonprofit that now focuses on everyone with type 1 diabetes, juvenile or not. The JDRF provides an instant community for people with type 1 diabetes through online forums, virtual events like summits and speakers, type 1 diabetes statistics, and information about care.

Beyond Type 1

Beyond Type 1 is the largest online diabetes organization. Their site features the latest news in diabetes care and treatments, personal stories from people with type 1, and links to other diabetes-related resources and programs.

Bloggers and influencers with type 1 diabetes

Our Diabetic Life

This blog follows Meri Schumacher, a mother of three children who were all diagnosed with type 1 diabetes before age 12.

Scott’s Diabetes

Diagnosed in 1980, Scott Johnson has been blogging about his type 1 diabetes journey since 2004. His archives cover a wide range of type 1 diabetes topics, as well his life as an avid cyclist, husband, and father.

Mohammad Al-Bahar @thediabetictraveler

Mohammad’s Instagram page is packed with inspirational quotes, fitness regimens, and travel tips for people who live with type 1 diabetes.

Lexie (@thedivabetic)

Lexie, known as the “divabetic,” is a Black diabetes advocate who posts everything from giveaways to advice on dating with type 1 diabetes. She frequently shares posts about diabetes-friendly food and humor.

FAQs: Frequently Asked Questions

Why did type 1 diabetes used to be called juvenile diabetes?

Most people with type 1 diabetes are diagnosed as children, although in rare cases some are not diagnosed until they are adults.

Are type 1 diabetes symptoms in adults different than in children?

No, adults and children experience the same symptoms.

Is there a type 1 diabetes cure?

Type 1 diabetes can be managed with insulin, but there is no cure.

In type 1 diabetes vs type 2, is diet as important?

Even though diet and lifestyle changes cannot reverse type 1 diabetes, and they have the potential of reversing type 2, learning what, how much, and when to eat can still help you have the most effective type 1 diabetes diet to manage your condition.

What type of doctor is best for type 1 diabetes treatment?

Even though an ER doctor or your primary care physician will likely be the one to first diagnose your type 1 diabetes, an endocrinologist is the best doctor to help you learn how to monitor your blood sugar and manage your condition.

Type 1 Diabetes Fast Facts

  • Type 1 diabetes affects about 1.6 million people in the US
  • Type 1 diabetes can be triggered by any virus, including a cold
  • People who have type 1 diabetes require insulin
  • Most people with TID are diagnosed in the ER as children
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What are the Symptoms of Type 1 Diabetes?