LADA: When Type 1 Diabetes Masquerades as Type 2 in Adults

Latent Autoimmune Diabetes in Adults (LADA), often referred to as "type 1.5 diabetes," is a slowly progressing form of autoimmune diabetes that frequently goes undiagnosed—especially in older adults. Unlike classic type 1 diabetes, which typically appears in childhood or adolescence, LADA develops gradually and can be easily mistaken for type 2 diabetes due to its late onset and initial responsiveness to oral medications. This case study explores how a misdiagnosis was corrected, leading to effective treatment and improved outcomes for a 65-year-old woman whose condition had been misunderstood for over a year.

Understanding the Diagnosis: From Mislabeling to Clarity

A growing number of adult patients are being diagnosed with what initially appears to be type 2 diabetes. However, when standard treatments fail to maintain stable blood glucose levels, further investigation becomes essential. In this instance, a 65-year-old female patient had been treated for presumed type 2 diabetes with metformin and later insulin therapy at a local clinic. Despite these interventions, her glycemic control continued to deteriorate—raising red flags about the accuracy of the original diagnosis.

Upon referral to Huashan Hospital, affiliated with Fudan University, clinicians conducted a comprehensive metabolic evaluation. Laboratory tests revealed significantly reduced fasting C-peptide and fasting insulin levels—clear indicators of declining pancreatic beta-cell function. More telling were the positive results for multiple autoantibodies: IAA (insulin autoantibodies), ICA (islet cell antibodies), and GADA (glutamic acid decarboxylase antibodies)—all hallmark markers of autoimmune destruction of insulin-producing cells.

The Key Differentiator: Autoimmunity vs Insulin Resistance

This antibody profile confirmed the true nature of her condition: she did not have type 2 diabetes driven by insulin resistance, but rather LADA—a subtype of type 1 diabetes characterized by gradual immune-mediated beta-cell loss. The distinction is critical because it directly influences treatment strategy, prognosis, and long-term management goals.

Precision Treatment Plan Based on Disease Mechanism

Given the patient's low fasting C-peptide level (≤0.3 mmol/L) and suboptimal response to basal insulin alone, a more tailored insulin regimen was initiated during her 10-day hospitalization in April 2022. Clinicians prescribed a combination therapy using both rapid-acting and long-acting insulins:

• Insulin Aspart Injection: A fast-acting insulin analog administered before meals to manage postprandial glucose spikes.
• Recombinant Glargine Insulin Injection: A long-acting basal insulin providing steady background insulin coverage throughout the day and night.

In addition to insulin therapy, the patient began taking oral vitamin D supplements. Emerging research suggests that vitamin D plays an immunomodulatory role and may help slow autoimmune activity in LADA patients, potentially preserving residual beta-cell function.

Dramatic Improvement in Glycemic Control

The results were striking. Within days of starting combination insulin therapy, the patient's blood glucose levels began stabilizing. By the end of her hospital stay, her fasting glucose had dropped from a peak of 18.6 mmol/L to a much healthier 5.8 mmol/L. Post-breakfast readings averaged around 7.2 mmol/L, well within target ranges recommended by international diabetes guidelines.

Follow-up testing showed no adverse drug reactions, and importantly, her C-peptide levels remained stable—suggesting that early intervention may have helped preserve remaining insulin production. The patient reported feeling more energetic, emotionally balanced, and confident in managing her health. She was discharged after 10 days with clear instructions and ongoing support plans.

Long-Term Follow-Up Shows Sustained Success

During subsequent outpatient visits, the patient maintained excellent adherence to her treatment plan. Her HbA1c decreased from an initial 7.4% to near-normal levels, and she experienced no episodes of severe hypoglycemia. Continuous monitoring confirmed sustained improvement in overall metabolic control, validating the decision to reclassify and treat her condition appropriately.

Essential Lifestyle & Management Recommendations

While medication is central to managing LADA, lifestyle choices play a vital supporting role. To ensure lasting success, patients should follow these evidence-based recommendations:

Medication Adherence and Monitoring

Never discontinue or adjust insulin doses without medical guidance. Even minor changes can lead to dangerous fluctuations in blood sugar. Regular self-monitoring of blood glucose (SMBG) allows for timely adjustments and helps prevent complications such as neuropathy, retinopathy, or cardiovascular disease.

Nutrition: Focus on Balance and Quality

A low-glycemic, nutrient-dense diet is ideal. Patients should limit refined sugars and processed carbohydrates while incorporating complex carbs, fiber-rich vegetables, lean proteins (such as fish, eggs, poultry, and legumes), and healthy fats. Portion control remains important to avoid post-meal surges in glucose.

Physical Activity and Sleep Hygiene

Engaging in moderate exercise—like brisk walking, swimming, or cycling—for at least 150 minutes per week improves insulin sensitivity and supports weight management. Additionally, maintaining a consistent sleep schedule, avoiding late nights, and reducing stress through mindfulness practices can positively influence metabolic health.

Safe Insulin Administration Practices

To prevent lipohypertrophy or injection site irritation, rotate insulin injection areas regularly—using different sites in the abdomen, thighs, or upper arms. Proper storage of insulin and use of sterile techniques also minimize risks of infection or ineffective dosing.

Clinical Insights: Why Early Recognition Matters

LADA accounts for approximately 2–12% of all adult-onset diabetes cases, yet it remains underrecognized. Many clinicians default to diagnosing type 2 diabetes in older adults, especially those who aren't classically lean or ketoacidosis-prone. But when oral agents stop working quickly or insulin requirements rise unexpectedly, autoimmunity must be considered.

The Role of Combination Insulin Therapy

The synergy between short- and long-acting insulin mimics natural insulin secretion patterns. Rapid-acting insulin aspart controls mealtime glucose excursions, while glargine provides a smooth, peakless basal supply—offering superior 24-hour control compared to single-agent regimens. This dual approach is particularly effective in patients with minimal endogenous insulin production.

Moreover, identifying LADA early opens doors to potential adjunct therapies aimed at modulating the immune system, including clinical trials exploring anti-CD3 antibodies, GAD vaccines, or low-dose immunosuppressants—all designed to prolong beta-cell survival.

Final Thoughts: Rethinking Adult-Onset Diabetes

This case underscores a crucial message: not all adult-onset diabetes is type 2. Physicians must maintain a high index of suspicion for autoimmune etiologies, especially when treatment responses deviate from expectations. Testing for GADA, ICA, and IAA in adults with apparent type 2 diabetes who show rapid progression or poor response to oral agents can uncover hidden cases of LADA.

Accurate diagnosis leads to precision medicine—and better quality of life. For patients, understanding their condition empowers them to take proactive steps in managing their health. With the right combination of insulin therapy, nutritional awareness, physical activity, and medical supervision, individuals with LADA can live full, active lives with excellent glycemic control.