What Is Type 1 Diabetes? Symptoms, Causes, Diagnosis, and Treatment

Type 1 diabetes is an autoimmune disease that leads the body to stop making enough insulin to keep glucose (sugar) at a healthy, normal level. It is most often diagnosed in children and young adults, although it can develop at any age. (1)

How Type 1 Diabetes Raises Blood Sugar

In the normal digestive process, your body breaks down much of the food you eat into glucose, a simple sugar that’s stored in your body and used for energy. The hormone insulin, produced by the pancreas, regulates the amount of glucose in your blood by helping liver, muscle, and fat cells absorb the sugar. (2)

With type 1 diabetes, the body’s immune system attacks and destroys the pancreas’s insulin-producing beta cells. Without that hormone, blood sugar rises too high, causing hyperglycemia.

“We don’t know exactly what triggers this autoimmune process to start,” says Charles Scott Thomas, MD, an endocrinologist at Kaiser Permanente Los Angeles Medical Center in Los Angeles. “There is likely a genetic component that places patients at risk, with some environmental influences as well.”

People who have type 1 diabetes must replace insulin every day through injections or infusion and monitor their blood glucose throughout the day. (1)

Type 1 vs. Type 2 Diabetes

Type 1 and type 2 diabetes produce the same result: blood sugar that is too high. But they do it in very different ways.

As mentioned, type 1 diabetes is an autoimmune disorder that results in the body being able to produce little or no insulin. It cannot be prevented. (3)

Type 2 diabetes develops when liver, muscle, and fat cells don’t respond properly to insulin and become “insulin resistant.” Glucose doesn’t enter the cells as efficiently as before and instead builds up in the bloodstream.

In type 2 diabetes, the pancreas responds to these increased blood glucose levels by producing more insulin. Eventually, however, it can no longer make enough insulin to handle spikes in glucose levels, such as routine rises in blood sugar after a meal.

Type 2 diabetes accounts for 90 to 95 percent of all diagnosed cases of diabetes. It can be prevented or delayed in many cases with diet and exercise changes. (4)

Symptoms of type 1 diabetes can develop rapidly, especially in young people, says Sanjoy Dutta, PhD, chief scientific officer for the type 1 diabetes research organization JDRF. Symptoms may include: (1)

• Excessive thirst
• Frequent urination
• Increased hunger
• Fatigue
• Blurry vision
• Unexplained weight loss

Dr. Dutta says sometimes the weight loss is very precipitous. “In some cases, it might even be 10 kilos (22 pounds) of weight loss within two weeks.”

The onset of type 1 diabetes can be difficult to detect in very young children, says Dr. Thomas. “The signs of something wrong may be more subtle, such as more wet diapers or heavier diapers, bedwetting, and increased thirst.”

Diabetic Ketoacidosis (DKA)

Another symptom of type 1 diabetes can be life-threatening, and particularly for young people who are less likely to understand what they are going through, says Dutta. Diabetic ketoacidosis (DKA) happens when insulin drops and the body can’t use your rising blood glucose as fuel; it turns to burning fat instead, leading to a too-rapid buildup of acids in the bloodstream, known as ketones. Symptoms of DKA can include: (5)

• Fruity-smelling breath
• Confusion or fatigue
• Difficulty breathing
• Dehydration
• Dry skin and mouth
• Facial flushing
• Increased urination or thirst
• Headache
• Achy or stiff muscles
• Stomach pain, nausea, or vomiting

It’s important to seek immediate medical attention for DKA, and it may involve a hospital trip. A blood or urine test for ketones can detect DKA. Treatment involves insulin injections and fluid replacement. (5)

Frequently, a bout of DKA is what leads to a diagnosis of type 1 diabetes, particularly in young people. Dutta says this can happen to anyone with type 1 diabetes at any age, but if a person develops the disease in their middle or later years, the progression is typically more gradual, and they are therefore more likely to already be under a doctor’s care for high blood sugar.

It’s unknown exactly what causes type 1 diabetes, but experts think it could be a combination of genetic and environmental factors. (1) For instance, the risk of type 1 diabetes is increased if you have certain variants of genes in the human leukocyte antigen (HLA) complex. These genes are involved in making proteins that play a critical role in immune response. (6)

Coxsackieviruses have been studied as possible triggers for type 1 diabetes, and prolonged viral infection may increase a child’s risk for developing the disease. (7)

Other possible risk factors for type 1 diabetes include:

• Being male. The risk of being diagnosed with type 1 diabetes is approximately 1.5 times higher for males than for females, says Thomas.
• Having autoantibodies that are associated with higher risk (1)
• Being of European descent (although people of any race or ethnicity can develop it). (8) Most white people with the disease have gene variants HLA-DR3 or HLA-DR4. (9)
• Having a close family relative who has type 1 diabetes (1)

In fact, the odds that a man with type 1 diabetes has a child who develops it are 1 in 17. For a woman who bears a child before age 25, that risk is 1 in 25, but it drops to 1 in 100 if the child is born after she is 25. (9)

Yet 80 percent of people with type 1 diabetes have no family history of the disease. (10)

“Testing for the diagnosis of type 1 diabetes first involves testing for abnormally high blood sugar,” says Thomas. “The next steps are uncovering if the high blood sugar is due to the pancreas having lost the ability to make adequate insulin, and testing for higher-than-normal levels of the antibodies that are often identified in type 1 diabetes.”

Blood Glucose Tests

Your healthcare provider may order the following tests to diagnose type 1 diabetes.

Random plasma glucose test, which checks if your blood sugar is too high and doesn’t require fasting before your blood sample is drawn. A reading higher than 200 milligrams per deciliter (mg/dL) with symptoms of high blood sugar indicates you have diabetes. (1,11)

Hemoglobin A1C test shows how high your blood sugar has been, on average, over the past three months. A blood sample is drawn, and it doesn’t require fasting beforehand. An A1C of 6.5 or higher indicates diabetes. (11)

Fasting plasma glucose test checks how high your blood sugar is after you’ve had nothing to eat or drink except small sips or water for at least eight hours. A reading higher than 126 mg/dL points to diabetes. (11)

Autoantibody Tests

Your doctor may order a diabetes autoantibody panel to detect autoantibodies that attack insulin or cells in the pancreas related to its production, as well as certain enzymes. (12)

Other Diagnostic Tests

The following may also be ordered to diagnose type 1 diabetes: (12)

• C-peptide test measures a by-product of insulin production and can show how much insulin your body is making, paired with a glucose value.
• Insulin assay test detects the levels of insulin in your blood, but is less commonly used and more variable than a C-peptide test.

Dutta recommends seeing an endocrinologist for treatment if you’re diagnosed with type 1 diabetes. “I’m not saying that a general practitioner will not be helpful, but a primary care physician doesn’t have the specialty knowledge to deal with type 1 diabetes, which is a very different disease from type 2 diabetes.”

Prognosis of Type 1 Diabetes

The average person with a type 1 diabetes diagnosis who makes it to age 43 has a life expectancy that is nearly eight years shorter than someone the same age without that diagnosis, according to a study published in 2020. (13)

That is slightly less than the life expectancy reported in a 2015 Scottish study that found men with type 1 diabetes at age 20 had a life expectancy about 11 years shorter than men who didn’t have the disease. For women, the decrease in life expectancy was 13 years, the study found. (14)

How well you manage type 1 diabetes can affect your life expectancy.

In another study, also published in 2015, researchers found that people with type 1 diabetes who underwent intensive treatment for 6.5 years experienced a modestly reduced risk of complications and a lower overall risk of early death. (15)

Type 1 diabetes is a lifelong illness that requires careful, daily management of blood sugar levels. “The constant need to be thinking about diabetes can grow tiresome and frustrating for many young people,” says Thomas. “While their journey will be different from the experience of those who don’t have type 1 diabetes, they can still live a fulfilling, successful life, and they may find that their unique experience gives them the ability to tap into an inner power they didn’t realize they had.”

Dutta strikes a similarly optimistic tone. “Do we have a cure? No. We have advances in the clinic, but not yet an approved therapy that cures type 1 diabetes.” But, he adds, continuing advances in glucose monitoring and insulin delivery are making it easier for people to manage life with the disease.

“The cornerstone of type 1 diabetes management continues to be insulin therapy,” says Thomas. Combined with glucose monitoring, this is the primary way that blood sugar is kept within a healthy range every day.

Insulin Therapy

Two main types of insulin are injected to get you through the day: (16, 17)

• Basal insulin is injected to stay in the body 24 hours a day, always, regardless of when you eat. Examples of intermediate- and long-acting insulins that are slowly released into the bloodstream so that they last include: isophane (Humulin N), detemir (Levemir), deludec (Tresiba), and glargine (Lantus).
• Bolus or mealtime insulin is injected to cover the glucose you get through food. The amount of bolus insulin you inject depends on the size of the meal you’ve just eaten. Examples of fast-acting or regular-acting insulin include insulin aspart (Novolog), insulin glulisine (Apidra), and insulin lispro (Humalog). Taken before a meal, they work within 15 to 30 minutes and keep working for several hours.

Insulin therapy typically involves injecting yourself up to several times daily using one of the following methods: (18)

• Needle and Syringe Insulin is drawn from a vial through a disposable needle and syringe (or the syringe is prefilled) and injected into fatty tissue just below the skin.
• Insulin Pen Using a device that either contains a prefilled cartridge of insulin or draws insulin from the cartridge through a disposable needle, you dial the dosage on the pen and then inject insulin beneath the skin through the needle.
• Insulin Pump A computerized device delivers insulin through a thin catheter that is inserted under the skin of the abdomen and kept in place with tape. “Patients provide information to the pump about the amount of carbohydrates they plan to eat and their current blood sugar level and the pump can suggest an insulin dose to deliver,” Thomas explains.

A slim majority of the 7.4 million insulin users in the United States (53 percent) were injecting with vials and syringes as of 2016, followed by prefilled insulin pen users (46 percent). (19) An estimated 350,000 people use pumps in the United States. (20)

Glucose Monitoring

An essential part of managing type 1 diabetes is glucose monitoring. People with the disease typically monitor their own blood sugar, using one of the following methods:

• Glucose Meter This is a portable device that analyzes a sample of your blood, which you collect by sticking your finger with a lancet and then placing the blood drop on a disposable test strip. The strip is then inserted into the meter. Talk to your healthcare provider to find the meter that is best for you, and check with your insurance plan to see which costs are covered. (21)
• Continuous Glucose Monitor (CGM) You wear this device around the clock while it measures and reports your blood sugar level. A tiny sensor that is thinner than a needle and around ½ inch long is inserted under the skin to measure glucose levels in the fluid between fat cells. A transmitter connected to the sensor sends the data to a receiver or smart device app. Dexcom G6, Freestyle Libre, and Medtronic Guardian Connect are among the most commonly used CGMs. (22)

“Patients are able to get real-time information about their blood sugar and also see trends,” says Thomas. That serves to help them to understand how food, sleep, exercise, and stress all affect their blood sugar, and how to avoid risky swings in glucose levels.

“When an insulin pump and CGM are integrated, the CGM can deliver information to the pump about the patient’s current blood sugar level and the trend of the blood sugar. This allows the pump to potentially alter insulin delivery to help maintain blood sugars more within a healthy range,” says Thomas. “While the patient still needs to be very involved with his or her own diabetes management, these devices offer a helping hand.”

Other Type 1 Diabetes Treatments

Less-common type 1 diabetes treatments include:

• Artificial Pancreas An increasingly common treatment, this cutting-edge device combines an insulin pump, a CGM, and a dosing algorithm, says Dutta. “The algorithm decides based on the CGM reading and the average over the last five minutes, to tell the pump, ‘You dose X number of units of insulin,’ and it goes up and down depending on your glucose levels.” Medtronic’s MiniMed 670G and 770G hybrid closed-loop systems, and Tandem Diabetes Care’s closed-loop Control-IQ are FDA-approved artificial pancreases, he says.
• Jet Injection Instead of a needle, an injector with an insulin cartridge delivers insulin beneath the skin via a jet of air. (24)
• Inhaled Insulin A rapid-acting inhaled insulin that you take at the beginning of each meal by breathing in powder through the mouth using an inhaler. It is sold under the brand name insulin inhalation (Afrezza). (17)
• Pramlintide This medication is taken with mealtime insulin and slows the movement of food through the stomach to keep blood sugar from spiking after a meal. (25)

Prevention of Type 1 Diabetes

Doctors aren’t aware of a way to prevent type 1 diabetes, but researchers have made progress and are continuing to explore ways to do so or at least slow its progression. (1)

For instance, the monoclonal antibody drug teplizumab was approved by the FDA in November 2022. Studies found it delayed the onset of type 1 diabetes by an average of two years in people who had relatives with the disease. (26,27)

Having prolonged high blood sugar can lead to a host of health problems. They include: (28)

• Heart disease
• Stroke
• Kidney disease
• Low blood sugar, or hypoglycemia
• Nerve damage
• Slow-healing wounds
• Foot problems
• Limb amputations
• Eye problems and blindness, or diabetic retinopathy
• Dental disease
• Bladder problems
• Sexual dysfunction

Having any type of diabetes can also put you at greater risk for complications from COVID-19, the respiratory disease caused by the novel coronavirus. “We know that patients with uncontrolled diabetes and COVID-19 infection experience more severe symptoms of COVID-19, can have more extensive lung involvement, and die more often,” says Thomas. Nearly 40 percent of COVID-19 deaths in the United States during the first few months of the pandemic happened to people who had diabetes. (29)

Managing Type 1 Diabetes: Diet and Exercise

There is no one-size-fits-all diet or exercise plan for people with type 1 diabetes. But a healthy lifestyle will help you keep your blood sugar in a healthy range. Be sure to speak with your doctor before embarking on any diet or exercise plan, to ensure you are making changes that are safe and appropriate for you. (30)

Diet

A registered dietitian nutritionist (RDN), and especially one who is also a certified diabetes care and education specialist (CDCES), can help you to find the meal plan that is right for you. Ask your healthcare provider for a referral or search the Academy of Nutrition and Dietetics directory for an RDN in your area. (31)

Whatever diet you settle on is likely to include some form of carb counting (monitoring your intake of carbohydrates, which break down into glucose); and a balance of protein, fat, and fiber to help stabilize blood sugar. (30)

Your healthcare team can help you decide the right balance, taking into account any medication or insulin you’re on. But the recommended amount of carbs for most people with diabetes in general is 45 to 65 percent of total daily calories. (32)

Keeping all that in mind, any healthy diet is likely to draw from the following, per federal guidelines: vegetables; fruits; whole grains; fat-free or low-fat milk and milk products (unless you are vegetarian); lean meats; poultry; fish; beans; eggs; and nuts and seeds. Keep your intake of saturated fats, cholesterol, salt, and added sugars to a minimum. Avoid trans fats. (33)

Exercise

Physical activity is another important aspect of diabetes management. Just make sure to check in with your healthcare provider before embarking on an exercise plan. Complications of diabetes, such as nerve damage or the risk of low blood sugar, may require adjustments in how you exercise. (34)

Taking that into account, aim for at least 150 minutes to 300 minutes a week of moderate-intensity exercise or 75 minutes to 150 minutes a week of vigorous-intensity aerobic physical activity. It’s moderate-intensity if you can talk, but not sing, during the activity; and vigorous-intensity activity if you can’t say more than a few words without pausing to take a breath. Again, your healthcare provider will help determine the right course of exercise. (35)

Type 1 affects people of all ages. Here are some more facts and figures on type 1 diabetes:

• Type 1 diabetes affects at least 1.4 million adults ages 20 years or older — or 5.2 percent of all adults who have been diagnosed with diabetes. (36)
• The agency also reports that at least 187,000 youths under age 20 have type 1 diabetes. (35)
• Each year there are an estimated 64,000 new cases of type 1 diabetes in people under age 64 in the United States (27,000 youths and 37,000 adults). (37)
• Type 1 diabetes treatment can be very expensive. The average yearly cost spent on insulin by people with type 1 diabetes was $5,705 in 2016. (19)

Although type 1 diabetes is most prevalent in the United States among white people, Hispanic (4.4 percent), non-Hispanic Asian and Pacific Islander (4.0 percent), and Black (2.7 percent) children and youths saw the steepest annual percentage increases in cases between 2002 and 2015. (38)

Youths of the Black, Indigenous, and People of Color (BIPOC) communities, particularly those who are socioeconomically disadvantaged, are more likely to have DKA at diagnosis, says Thomas. The authors of a 2018 study (in which Thomas was not involved) surmised that insurance access and parent education accounted for much of the difference. (39)

As mentioned, type 1 diabetes is a lifelong disease that requires active management throughout the day, every day. This reality can be daunting for someone who has just received a diagnosis. Dutta advises that you find out as much as you can, and don’t be afraid to speak up or seek help. “Learn about the disease. Knowledge is power,” he says.

“And do not be shy, do not stay in the closet about it, because it is a very socially challenging disease. Be open about it and remember: You didn’t get it because you did something wrong or you were eating too much.” He also advises that you participate in clinical trials if you are able to, to aid the development of treatments, and — eventually — a cure.

The following resources can help you learn more about the disease, seek support, get help affording your medication, manage life with type 1 diabetes, and participate in research trials.

Favorite Orgs for Essential Diabetes Info

JDRF

This nonprofit is among the most prominent in the United States focused specifically on type 1 diabetes research and advocacy. Its offerings are vast, with chapters nationwide, and they include a wealth of resources in English and Spanish to help you navigate life with the disease. You can also get matched with outreach volunteers who have a close personal connection to type 1 diabetes, and they can help you cope. They can also help you learn how to use their clinical trials matching tool. And because insulin therapy can be so expensive, they also provide a guide to navigating health insurance, and information on other ways to afford your medication.

American Diabetes Association

The largest organization in the United States focusing on all types of diabetes, it is a treasure trove of information about the disease, in part because of its prominent role in the research world through a professional society that hosts yearly conferences; its highly respected, peer-reviewed journals; and a key role setting standards of diabetes care in the United States. They advocate for legislation to make insulin more affordable, and host InsulinHelp.org, a guide to information about drug manufacturer’s patient assistance programs.

Favorite Online Support Networks

Beyond Type 1

A frequent partner with JDRF, Beyond Type 1 is a social-media-savvy nonprofit focused on advocacy and insulin affordability. Join their social platform by connecting through Facebook or Apple, among other providers. Or, visit their GetInsulin.org guide for information about affording the medication and help devising an action plan to get it.

The Diabetes Link

This peer-support-focused nonprofit is focused on forging connections between and among students in high school and college with type 1 diabetes. Get advice for navigating care through the transition between high school and college, read blog posts written by college students, or find a college chapter to join.

Favorite Clinical Trial Resources

TD1 Exchange

The heart of this data-driven nonprofit is a registry of people with type 1 diabetes that gathers information used in research about the disease. Community members — 28,000 are registered — answer a question a day and interact with each other online. The organization says its research has led to advances relating to CGM labeling and insurance coverage, as well as updated guidelines for pediatric A1C goals.

Type 1 Diabetes TrialNet

This global network of type 1 diabetes researchers focused on finding ways to prevent type 1 diabetes. They offer free type 1 diabetes risk screening to relatives of people with the disease through the Pathway to Prevention Study. The goal is to detect type 1 diabetes even years before symptoms appear, and identify people who are at risk for developing it. Among the studies coming out of TrialNet to date was the phase 2 clinical trial for teplizumab. As mentioned, the study found that the monoclonal antibody drug delays the onset of type 1 diabetes in close relatives by an average of two years.

Favorite Type 1 Diabetes Apps

Glooko

Many glucose monitoring devices have their own apps for receiving and analyzing your diabetes data; but Glooko allows you to sync that data with their platform to help you understand how food, activity, and medication affect your glucose levels. The list of compatible devices is a long one, and you can also sync it with popular activity apps such as Runkeeper, Strava, Apple Health, and Fitbit. View your glucose trends, use a barcode scanner to add foods to your log, set medication reminders, and more. It has 4.7 stars in the Apple Store and also 4.0 stars in GooglePlay.

MyFitnessPal

Many people use this popular app’s free fitness log and interactive food diary in order to keep track of how many calories they are taking in and burning off each day. But if you upgrade to the premium monthly plan of $9.99, you can also track your carb intake and search for low-carb recipes. When you choose an activity or food, the nutrients attached are automatically added to your daily tracker. Download it in the Apple Store (where it has 4.7 stars) or GooglePlay (where it has 4.2 stars).

Additional reporting by Joseph Bennington-Castro.