Type 1 Diabetes: Symptoms, Causes, Treatment and More

Type 1 diabetes is a chronic disease where the body cannot produce insulin, a hormone needed to control blood sugar levels. Without insulin, glucose builds up in the blood instead of being used by cells for energy. This condition affects millions of people worldwide and requires daily management to prevent serious health complications. In the United States alone, more than 2 million people have type 1 diabetes (1).

Type 1 diabetes was previously known by other names including insulin-dependent diabetes mellitus (IDDM), juvenile diabetes, and brittle diabetes. Today, these terms are rarely used as we better understand the condition.

What Is Type 1 Diabetes?

Type 1 diabetes occurs when the immune system mistakenly attacks and destroys the insulin-producing cells in the pancreas. This leaves the body unable to make insulin on its own. In 2021, about 8.4 million people worldwide had type 1 diabetes, with 1.5 million being younger than 20 years old (2).

The condition can develop at any age, though it often appears in childhood or young adulthood. Type 1 diabetes shows two peak ages for diagnosis: between 4-7 years and 10-14 years. Research shows that only 6% of people with type 1 diabetes are in the 0-14 age group, while 35% are aged 15-39, and 43% are aged 40-64 (3). The global prevalence of type 1 diabetes is 5.9 per 10,000 people, with the highest rates in Finland and Saudi Arabia, and the lowest in China and Venezuela (4).

Symptoms of Type 1 Diabetes

The symptoms of type 1 diabetes often develop quickly over a few weeks. Common symptoms include:

• Excessive thirst and frequent urination
• Extreme hunger
• Unexplained weight loss
• Fatigue and weakness
• Blurred vision
• Slow healing of cuts and wounds

The “polyuria-polydipsia syndrome” (excessive urination and thirst) is one of the most characteristic presentations (5). These symptoms occur because high blood sugar causes the kidneys to work overtime to filter excess glucose, leading to increased urination and subsequent dehydration.

The classic triad of symptoms includes polyuria (excessive urination), polydipsia (excessive thirst), and unexplained weight loss. About 30% of children with type 1 diabetes present with this symptom triad at diagnosis (6).

Symptoms can vary by age. In young children, new bedwetting in a previously toilet-trained child can be an early sign. Diabetic ketoacidosis can be the first presentation of type 1 diabetes, requiring immediate medical attention (7).

In severe cases, a life-threatening condition called diabetic ketoacidosis (DKA) can develop. This happens when the body starts breaking down fat for energy, producing acids called ketones. Between 15-70% of children are diagnosed with type 1 diabetes when they develop DKA (8).

The Honeymoon Phase

After diagnosis and starting insulin treatment, some people experience what’s called the “honeymoon phase.” During this time, the pancreas may still produce small amounts of insulin, leading to lower insulin requirements.

This phase can last weeks to months, and blood sugar levels may seem easier to control. However, this doesn’t mean the diabetes is going away. The remaining insulin-producing cells will eventually stop working, and full insulin replacement will be needed. The honeymoon period occurs in about 71% of children with type 1 diabetes, typically starting about a month after diagnosis. The average duration is 7.2 months, though it can range from 1 month to 13 years (9). On average, the remission phase appears about 3 months after insulin therapy starts, with the duration of partial remission averaging 9.2 months (10).

It’s important to continue regular blood sugar monitoring and insulin therapy during this phase, even if doses are reduced. Your healthcare team will help adjust your treatment as needed.

What Causes Type 1 Diabetes?

Type 1 diabetes results from a complex interaction between genetic factors and environmental triggers.

Genetic Factors

Having certain genes increases the risk of developing type 1 diabetes. The HLA-DR3 and HLA-DR4 genes play important roles. About 35% of people with type 1 diabetes have both DR3 and DR4 genes (11). Other HLA genes, including HLA-DPB1, also contribute to risk, though their effect is smaller (12).

Risk genes can vary by population. For example, in Egyptian children, 77.2% with type 1 diabetes carry the high-risk DR3-DQ2 gene combination (13).

The role of genetics is complex. Even identical twins don’t always both develop type 1 diabetes – if one twin has it, the other develops the condition only about half the time. This shows that genes alone don’t determine who gets type 1 diabetes (14).

If you have a parent with type 1 diabetes, your risk is higher. When a parent has the condition, 78% of the time they pass on the DR4 gene to children who also develop diabetes (11).

The risk increases if multiple family members have type 1 diabetes. In families where one child has type 1 diabetes, siblings have a 13.5% chance of developing it too (15).

Environmental Triggers

Viral infections may trigger type 1 diabetes in people who are genetically susceptible. Enteroviruses, in particular, show a strong link to the condition. People with type 1 diabetes are 9.8 times more likely to have had an enterovirus infection (16).

Environmental chemicals might also play a role. Studies have found associations between type 1 diabetes and exposure to air pollution, arsenic, and persistent organic pollutants, though more research is needed to understand these connections (17). The possibility that environmental chemicals contribute to type 1 diabetes through endocrine disruption is being actively investigated (18).

Psychological stress may also play a role in triggering type 1 diabetes. Studies suggest that stressful life events can increase the risk of developing the condition in genetically susceptible individuals (19).

Other Risk Factors

Geography plays a role in type 1 diabetes risk. Countries farther from the equator tend to have higher rates of type 1 diabetes. Finland has the highest incidence in the world. This variation might be related to differences in sunlight exposure, vitamin D levels, or viral infections in different regions (6).

Certain environmental factors might protect against type 1 diabetes. Some research suggests that early exposure to common germs (the hygiene hypothesis) or specific dietary factors during infancy might influence risk (20).

Autoantibodies in Type 1 Diabetes

Before symptoms appear, the immune system produces autoantibodies that attack the pancreas. These antibodies can be detected in blood tests and help predict who might develop type 1 diabetes.

The main autoantibodies include:

• Antibodies to insulin (IAA)
• Antibodies to glutamic acid decarboxylase (GADA)
• Antibodies to tyrosine phosphatase (IA-2A)
• Antibodies to zinc transporter 8 (ZnT8A)

Testing for these four antibodies can identify 93-96% of people with type 1 diabetes (21). Children with multiple autoantibodies have a high risk of progression to diabetes. Research shows that about 70% of children with two or more autoantibodies progress to type 1 diabetes within 10 years (65).

Diagnosis of Type 1 Diabetes

Doctors diagnose type 1 diabetes using several blood tests:

Blood Sugar Tests

A diagnosis of diabetes is made when:

• Fasting blood sugar is 126 mg/dL or higher on two separate tests
• Random blood sugar is 200 mg/dL or higher with symptoms
• HbA1c (average blood sugar over 2-3 months) is 6.5% or higher on two tests

The HbA1c test is particularly useful because it shows blood sugar control over time rather than just at one moment (22).

Distinguishing Type 1 from Type 2

To confirm type 1 diabetes, doctors test for autoantibodies. The presence of these antibodies indicates type 1 rather than type 2 diabetes. About 5-10% of all diabetes cases are type 1 (3).

Treatment of Type 1 Diabetes

People with type 1 diabetes need lifelong insulin therapy since their bodies cannot produce insulin.

Insulin Therapy

Different types of insulin work at different speeds and last for different lengths of time:

• Rapid-acting insulin: starts working within 15 minutes and lasts about 4 hours. Examples include lispro, aspart, and glulisine. Studies show that rapid-acting insulin analogues provide better glycemic control compared to regular human insulin. A systematic review found that insulin aspart provides greater reduction in HbA1c and improves postprandial glucose levels in both type 1 and type 2 diabetes (23). Rapid-acting insulin analogues are more effective than regular human insulin at reducing after-meal blood sugar spikes and lowering HbA1c in people with type 1 diabetes (24).
• Long-acting insulin: provides steady insulin levels for up to 24 hours. Insulin glargine is one example that provides constant, peakless coverage (25). Long-acting insulin analogues reduce HbA1c compared to intermediate-acting NPH insulin, with glargine once daily, detemir once daily, and detemir once/twice daily showing significant improvements (26).

Most people use a combination of rapid-acting insulin with meals and long-acting insulin for background coverage.

Insulin Delivery Methods

Insulin can be delivered through:

• Syringes and vials: The traditional method
• Insulin pens: Pre-filled devices that are easier to use
• Insulin pumps: Small devices that deliver insulin continuously through a tube under the skin
• Sensor-augmented pumps: Insulin pumps combined with continuous glucose monitors that work together. These systems lower HbA1c more than traditional methods, with a 0.68% greater reduction compared to multiple daily injections (27).

Studies show that insulin pumps and multiple daily injections achieve similar blood sugar control when used alone (27).

Other Insulin Options

• Inhaled Insulin: Rapid-acting inhaled insulin (Afrezza) provides an alternative to injections for mealtime insulin. It works within minutes and can be convenient for some people. Studies show inhaled insulin is non-inferior to injected rapid-acting insulin for HbA1c control, though fewer people achieve HbA1c below 7% (28). Inhaled insulin also provides better after-meal blood sugar control compared to injected insulin (29).

Blood Sugar Monitoring

Regular blood sugar monitoring is essential for managing type 1 diabetes. Options include:

• Finger-stick testing: Checking blood sugar with a glucose meter several times daily. Home self-monitoring of blood glucose is standard practice for people with type 1 diabetes (30).
• Continuous glucose monitoring (CGM): Devices that check blood sugar every few minutes through a sensor under the skin. CGM users achieve better blood sugar control, with HbA1c levels 0.26% lower than those using finger-stick testing alone (27). Real-time CGM also reduces the risk of severe hypoglycemia (31).

Flash glucose monitoring systems, which require scanning a sensor to get readings, also improve outcomes. These systems reduce time spent in hypoglycemia and increase treatment satisfaction, though effects on HbA1c are modest (32).

Real-time CGM has been shown to be superior to self-monitoring of blood glucose in multiple studies (33).

Blood Sugar Targets

Healthcare providers set blood sugar goals to help prevent complications while avoiding dangerous lows. General targets for adults include:

• Before meals: 80-130 mg/dL
• Two hours after meals: Less than 180 mg/dL
• HbA1c: Less than 7% for most adults
• Time in range (70-180 mg/dL): Greater than 70% when using CGM

These targets are based on current medical guidelines to balance good control with safety (34). Time in range metrics are increasingly used alongside HbA1c to assess glucose control (35).

These targets may be adjusted based on age, other health conditions, and individual circumstances. Children, older adults, and people with frequent low blood sugar may have different targets.

Carbohydrate Counting

People with type 1 diabetes need to count carbohydrates in their food to calculate insulin doses. The carbohydrate-to-insulin ratio varies by meal time. Studies show this ratio is approximately 300 divided by total daily insulin for breakfast, or 400 divided by total daily insulin for lunch and dinner (36).

Learning carbohydrate counting improves quality of life and helps with weight management. People using this method are better able to match their insulin to their food intake (37).

Insulin-to-carbohydrate ratios can be visualized and better understood using pharmacokinetic models that show how different insulin types work in the body over time (38).

Other Medications

Some people with type 1 diabetes benefit from additional medications:

• Metformin: Usually used for type 2 diabetes, it can help some people with type 1 diabetes who need very high insulin doses. However, studies show mixed results about its effectiveness (39). A systematic review found no clear benefit of metformin for HbA1c reduction in type 1 diabetes (40).
• Pramlintide: A synthetic hormone that can help reduce blood sugar spikes after meals (41).
• Heart Protection Medications: Because people with type 1 diabetes have higher heart disease risk, doctors may prescribe:
  • Low-dose aspirin to reduce heart attack and stroke risk
  • Cholesterol-lowering medications (statins) even if cholesterol levels are normal
  • Blood pressure medications, particularly ACE inhibitors or ARBs, which also protect the kidneys

Complications of Type 1 Diabetes

High blood sugar levels over time can damage blood vessels and nerves throughout the body, leading to serious complications.

Short-term Complications

• Hypoglycemia (Low Blood Sugar): This occurs when blood sugar drops too low, usually from taking too much insulin. Symptoms include shaking, sweating, confusion, and in severe cases, loss of consciousness.For severe hypoglycemia when a person cannot swallow or is unconscious, glucagon injection or nasal spray can be life-saving. Family members and close friends should know how to give glucagon in emergencies.Some people develop hypoglycemia unawareness, where they lose the ability to feel symptoms of low blood sugar. This can be dangerous because they may not realize they need treatment. People who experience frequent lows are more likely to develop this condition. Working with your healthcare team to avoid lows for several weeks can help restore awareness.
• Diabetic Ketoacidosis (DKA): This life-threatening condition develops when the body doesn’t have enough insulin. The annual incidence of DKA in adults with type 1 diabetes ranges from 0 to 56 per 1,000 person-years (42).

Long-term Complications

Good blood sugar control can significantly reduce the risk of complications. The landmark DCCT study showed that intensive blood sugar control reduced complications by 34-76% (43).

In people with recent-onset type 1 diabetes who underwent hematopoietic stem cell transplantation, 20 out of 23 patients became insulin-free for periods ranging from months to years. The continuous insulin-independent group maintained HbA1c levels below 7% and showed significant increases in C-peptide levels (a marker of insulin production) (44).

Major complications include:

• Eye problems (retinopathy): Can lead to vision loss
• Kidney disease (nephropathy): May progress to kidney failure
• Nerve damage (neuropathy): Causes pain, numbness, and other problems
• Heart disease: People with type 1 diabetes have a higher risk
• Foot problems: Poor circulation and nerve damage can lead to serious infections and possible amputation
• Skin and mouth conditions: Including bacterial and fungal infections, gum disease, and dry mouth
• Mental health conditions: People with diabetes are 2-3 times more likely to have depression and 20% more likely to have anxiety

About 50% of people with type 1 diabetes will develop a serious complication over their lifetime. However, good blood sugar control significantly reduces these risks.

Current incidence of type 1 diabetes worldwide shows it continues to increase by about 3% annually (2).

The benefits of good blood sugar control last for many years. Even after blood sugar control becomes similar between groups, people who previously had tight control continue to have fewer complications – a phenomenon called “metabolic memory” (43).

Living with Type 1 Diabetes

Managing type 1 diabetes requires daily attention but doesn’t have to limit your life.

Daily Management

Key aspects of daily diabetes management include:

• Checking blood sugar regularly
• Taking insulin as prescribed
• Counting carbohydrates at meals
• Staying physically active
• Managing stress
• Getting enough sleep

Comprehensive lifestyle management, including healthy eating, physical activity, and stress management, is fundamental to diabetes care (45).

Diet and Exercise

People with type 1 diabetes can eat a normal, healthy diet. The key is learning to match insulin doses to food intake. Limiting ultra-processed foods can improve overall dietary quality and health outcomes (46).

Regular exercise helps control blood sugar but requires careful planning to avoid low blood sugar. Aim for at least 150 minutes of moderate aerobic exercise per week, spread over at least 3 days with no more than 2 consecutive days without exercise. While research in type 2 diabetes shows that moderate-intensity exercise after dinner can improve blood sugar control (47), people with type 1 diabetes need to be especially careful with timing and insulin adjustments.

Exercise can help individuals achieve better glucose control, body composition, and fitness goals. However, barriers such as fear of hypoglycemia require proper management strategies including blood glucose monitoring and nutritional adjustments (48).

Always check blood sugar before exercising and carry fast-acting carbohydrates to treat potential lows. You may need to adjust insulin doses or eat extra carbohydrates before, during, or after exercise.

Different types of exercise affect blood sugar differently. Resistance exercise may require different management strategies than aerobic exercise (49).

Special Situations

• Pregnancy: Women with type 1 diabetes can have healthy pregnancies with careful planning and management. Tight blood sugar control before and during pregnancy is crucial. Studies show that with good glycemic control, pregnancy outcomes are comparable between teenage and young adult mothers with type 1 diabetes (50).The use of continuous glucose monitoring during pregnancy is associated with improved neonatal outcomes, including lower rates of large babies and neonatal intensive care admissions (51).
• Driving: People with type 1 diabetes can drive safely but need to check blood sugar before driving and carry treatment for low blood sugar (52).
• Alcohol: Alcohol can cause delayed low blood sugar, sometimes many hours after drinking. People with type 1 diabetes need to be extra careful with alcohol and should never drink on an empty stomach (53).
• Travel: People with type 1 diabetes can travel safely with proper planning. This includes bringing extra supplies, keeping insulin at proper temperatures, and adjusting insulin doses for time zone changes. Air travel poses specific challenges including insulin storage and adjustment for changing time zones (54).Recent advances in closed-loop insulin delivery systems have made travel easier by automatically adjusting insulin delivery (55).
• Sick Days: Illness can affect blood sugar control and increase the risk of diabetic ketoacidosis. Having a sick day plan that includes more frequent blood sugar monitoring, ketone testing, and knowing when to seek medical help is important (56).Sick day management should include guidelines for insulin dose adjustments, fluid intake, and when to seek medical care (57).

Future Treatments and Research

Research continues to advance treatment options for type 1 diabetes.

Artificial Pancreas Systems

These systems combine a continuous glucose monitor with an insulin pump that automatically adjusts insulin delivery. Hybrid closed-loop systems are already available and show promising results in improving blood sugar control (58).

Both wearable artificial pancreas systems for outpatient use and bedside systems for hospital use have shown significant benefits in glycemic control (59).

Cell Therapy

Researchers are working on ways to replace the destroyed insulin-producing cells. Some approaches include:

• Transplanting insulin-producing cells from donors
• Creating new insulin-producing cells from stem cells
• Re-educating the immune system to stop attacking the pancreas

Pancreatic Islet Transplantation: This experimental procedure involves transplanting insulin-producing cells from a donor pancreas into a person with type 1 diabetes. While promising, it’s currently only available in research settings. People receiving transplants need to take immunosuppressive drugs to prevent rejection. Recent progress in islet transplantation has resulted in substantial improvements in metabolic and safety outcomes. For patients with type 1 diabetes, islet transplantation can ameliorate problematic hypoglycemia, stabilize glycemic lability, and maintain on-target glycemic control, often without requiring insulin therapy (60).

Early studies show that stem cell-derived pancreatic cells can produce insulin in response to meals in people with type 1 diabetes (61).

Prevention Research

Scientists are studying ways to prevent type 1 diabetes in people at high risk. New drugs that may delay the onset of type 1 diabetes in at-risk individuals are being tested. A comprehensive review of disease-modifying immunotherapies found that both nonantigen-based and antigen-based immunotherapies show promise in preserving beta cell function (62).

Beta Cell Protection: Some medications may help protect the remaining insulin-producing cells in newly diagnosed patients. For example, verapamil, a blood pressure medication, has shown promise in preserving beta cell function in adults with recent-onset type 1 diabetes (63).

Support and Resources

Living with type 1 diabetes can be challenging, but support is available.

Healthcare Team

A diabetes care team typically includes:

• Endocrinologist (diabetes specialist)
• Diabetes educator
• Dietitian
• Mental health professional
• Eye doctor
• Foot doctor (podiatrist)

Regular check-ups help prevent complications and adjust treatment as needed.

Technology and Tools

Modern technology makes diabetes management easier:

• Smartphone apps for tracking blood sugar and carbohydrates
• Online communities for support and information
• Telemedicine for remote consultations
• Advanced glucose monitors and insulin pumps

Mental Health

Living with a chronic condition can be stressful. It’s important to address mental health alongside physical health. Support groups, counseling, and stress management techniques can all help. Parents of children with type 1 diabetes often experience high levels of stress, anxiety, and depression related to managing their child’s condition. Research shows that interventions aimed at improving diabetes management and decreasing stress can help by increasing parental self-efficacy (64).

The Bottom Line

Type 1 diabetes is a serious but manageable condition. While it requires daily attention and lifelong treatment, people with type 1 diabetes can live full, active lives.

With proper management, the risk of complications can be greatly reduced. Research continues to improve treatments and may one day lead to a cure. Until then, the tools and knowledge available today allow people with type 1 diabetes to thrive.