Type 1 Diabetes: Symptoms, Causes and Complete Treatment [2026]

Type 1 Diabetes Mellitus - an autoimmune disease in which the immune system attacks and destroys beta cells in the pancreas, those responsible for producing insulin. Unlike type 2 diabetes, type 1 diabetes mellitus is not caused by lifestyle and cannot be prevented. It represents approximately 5-10% of all diabetes cases worldwide and is most frequently diagnosed in children, adolescents, and young adults - although it can appear at any age. People with type 1 diabetes depend on exogenous insulin every day, throughout their lives. In this comprehensive guide, the Prime Medical team and Dr. Daniela Petrache explain everything you need to know: from symptoms and diagnosis, to modern insulin treatment and continuous monitoring with LinX CGM.

What is type 1 diabetes mellitus?

Type 1 diabetes mellitus (formerly known as "insulin-dependent diabetes" or "juvenile diabetes") is a chronic autoimmune disease in which the immune system mistakenly attacks pancreatic beta cells - the only cells in the body capable of producing insulin. Without insulin, glucose from the blood can no longer enter cells to be converted into energy, and blood glucose levels rise dangerously high.

In type 1 diabetes mellitus, two main mechanisms occur:

1. Autoimmune destruction of beta cells - antibodies produced by the immune system (GAD65, IA-2, ZnT8, IAA) progressively attack and destroy insulin-producing cells in the pancreatic Langerhans islets. When approximately 80-90% of beta cells are destroyed, symptoms become manifest

2. Absolute insulin deficiency - unlike type 2 diabetes, where the pancreas still produces some insulin (but cells don't use it efficiently), in type 1 insulin production is almost or completely absent. Therefore, insulin therapy is mandatory from the moment of diagnosis

Disease onset is usually acute, within days or weeks, not gradual as in type 2 diabetes. Two well-documented peaks of incidence are between 4-7 years and between 10-14 years. However, approximately 50% of new cases are diagnosed in adults - including a slower-progressing form called LADA (Latent Autoimmune Diabetes in Adults).

Symptoms of type 1 diabetes mellitus - acute onset, not gradual

Unlike type 2 diabetes, which can develop silently for years, type 1 diabetes mellitus has a rapid and dramatic onset. Symptoms usually appear within days or weeks and worsen progressively if not recognized.

The 4 classic symptoms (known as "the 4Ps") are:

• Polyuria - frequent and abundant urination, including at night (nocturnal enuresis in children who were already "dry")

• Polydipsia - excessive, constant thirst, which does not respond to normal hydration

• Polyphagia - marked hunger, even though the person eats enough or even more than usual

• Weight loss - rapid and unexplained weight loss, sometimes 5-10 kg in a few weeks

Other frequent symptoms include:

• Extreme fatigue and marked weakness sensation

• Blurred vision

• Irritability and mood changes (especially in children)

• Frequent infections - candidiasis, urinary tract infections

• Slow wound healing

Causes and risk factors for type 1 diabetes mellitus

Type 1 diabetes mellitus is an autoimmune disease with complex etiology. It is not caused by sugar consumption, excess weight, or lack of physical activity - these factors are relevant for type 2 diabetes, not type 1. The exact cause remains incompletely understood, but research has identified three categories of factors involved:

Genetic factors

• HLA genes (human leukocyte antigens) - especially HLA-DR3 and HLA-DR4, located on chromosome 6, are the strongest genetic risk factor. Approximately 90% of people with type 1 diabetes have at least one of these gene variants

• Family history - if one parent has type 1 diabetes, the child's risk is 3-8%; if both parents have the disease, the risk increases to 30%. However, 85% of new cases occur in people without a family history of type 1 diabetes

• Other genes - over 60 genetic loci have been associated with increased risk, including the insulin gene (INS) and the CTLA-4 gene

Autoimmune factors

• Autoantibodies - the presence of two or more specific autoantibodies (GAD65, IA-2, ZnT8, IAA, ICA) is a strong predictor of type 1 diabetes development. Autoantibodies can be detected months or even years before clinical onset

• Association with other autoimmune diseases - people with type 1 diabetes have increased risk of Hashimoto's thyroiditis (present in 20-25% of patients), celiac disease (5-10%), adrenal insufficiency (Addison's disease), vitiligo, and pernicious anemia

Environmental factors (triggers)

Genetic predisposition alone is not sufficient - an environmental trigger factor is needed that "starts" the autoimmune reaction:

• Viral infections - Coxsackie B viruses, enteroviruses, rubella, and rotavirus have been associated with triggering the autoimmune process in genetically predisposed people

• Perinatal factors - cesarean delivery, early introduction of cow's milk (controversial), vitamin D deficiency in early childhood

• Intestinal microbiome - reduced diversity of intestinal flora in early childhood has been associated with increased risk of pancreatic autoimmunity

• Hygiene hypothesis - reduced exposure to pathogens in childhood may dysregulate the immune system, contributing to autoimmune diseases

How is type 1 diabetes mellitus diagnosed?

Diagnosis is based on the same blood glucose thresholds as for type 2 diabetes, but includes additional tests specific to confirming the autoimmune nature of the disease:

Tests specific to type 1 diabetes

To differentiate type 1 diabetes from type 2 (especially in adults), the doctor orders additional tests:

• Pancreatic autoantibodies:

  • Anti-GAD65 (Glutamic Acid Decarboxylase) - most frequently positive, present in ~70% of patients

  • Anti-IA-2 (Islet Antigen 2) - positive in ~60% of patients

  • Anti-ZnT8