Type 1 diabetes is being missed in young, lean adults who don't fit the typical type 2 profile, leading to dangerous delays in treatment. A 32-year-old woman recently arrived at an emergency department with severe symptoms including vomiting, abdominal pain, and extreme fatigue. Instead of being screened for type 1 diabetes, she was sent home on metformin, a medication for type 2 diabetes, and told to follow up with her primary care doctor. Days later, she returned in diabetic ketoacidosis, a life-threatening condition where the body produces too many ketones and the blood becomes dangerously acidic .

This case highlights a critical gap in how emergency departments and primary care providers approach diabetes diagnosis. The patient had been diagnosed with prediabetes two years earlier based on an A1C (a measure of average blood sugar over three months) of 6.2%. She was lean, athletic, had no family history of diabetes, and was only 32 years old. Yet when she developed acute symptoms, doctors assumed type 2 diabetes and prescribed metformin without investigating whether she might have type 1 diabetes instead .

What's the Difference Between Type 1 and Type 2 Diabetes?

Type 1 diabetes is an autoimmune condition where the body's immune system attacks the cells in the pancreas that produce insulin, the hormone that regulates blood sugar. Type 2 diabetes develops when the body becomes resistant to insulin or doesn't produce enough of it, and it's typically associated with age, weight, and family history. The two conditions require completely different treatment approaches. Type 1 requires insulin from day one; type 2 often starts with lifestyle changes and oral medications like metformin .

The problem is that type 1 diabetes can develop at any age, including in adulthood. When it appears in adults, it's sometimes called latent autoimmune diabetes in adults (LADA) or adult-onset type 1 diabetes. Because doctors often associate type 1 with children and type 2 with adults, they may miss the diagnosis in older patients who don't fit the expected profile .

How Can Doctors Catch Type 1 Diabetes Earlier?

According to Dr. Anne L. Peters, a professor of clinical medicine at the University of Southern California who specializes in diabetes care, there are several red flags that should prompt testing for type 1 diabetes in young adults. The key is recognizing who is at risk and testing appropriately before symptoms become severe .
Dr. Anne

Age and Body Type: Patients under 35 years old who are lean or have a normal weight should be considered for type 1 diabetes screening, especially if they lack a family history of type 2 diabetes.
Islet Autoantibody Testing: When a young, lean patient presents with prediabetes, doctors should measure islet autoantibodies, which are antibodies that attack the insulin-producing cells in the pancreas. A positive result indicates type 1 diabetes, not type 2.
Symptom Recognition: Rapid weight loss, increased urination, extreme fatigue, and abdominal pain in a previously healthy young person should raise suspicion for type 1 diabetes, not type 2.
Medication Triggers: Certain medications can unmask underlying type 1 diabetes. In this case, the patient was started on spironolactone for acne, which caused increased urination and weight loss that accelerated her diabetes onset.

"I think this is a commonly missed diagnosis. I've seen it often missed in college students. We need to make people more aware that this could be new-onset type 1, and at the very least, give patients some instruction on how to give insulin and make sure that they get discharged to a provider who can help follow them," said Dr. Anne L. Peters, Professor of Clinical Medicine at the University of Southern California.
Dr. Anne L. Peters, Professor of Clinical Medicine, University of Southern California

In the case described, the patient had prediabetes diagnosed two years earlier. If her doctors had tested for islet autoantibodies at that time, they likely would have discovered she had pre-type 1 diabetes, not pre-type 2 diabetes. This early detection could have opened the door to preventive treatments like teplizumab, a medication that may slow or prevent the progression to full type 1 diabetes .

What Happens When Type 1 Diabetes Is Caught Late?

When type 1 diabetes goes undiagnosed and untreated, blood sugar levels can spike dangerously high. The body, unable to use glucose for energy, begins breaking down fat instead, producing ketones as a byproduct. When ketone levels become too high, the blood becomes acidic, leading to diabetic ketoacidosis (DKA). This is a medical emergency that requires hospitalization and intravenous insulin treatment .

In this patient's case, her A1C had climbed to 11.5% by the time she was properly diagnosed, indicating severely elevated blood sugar over the previous three months. She required hospitalization, intravenous insulin, and discharge on two types of insulin: glargine (a long-acting insulin) and a rapid-acting insulin for meals. The good news is that with proper management and support, she has responded well to treatment .

Why Continuous Glucose Monitors Matter for New-Onset Type 1 Diabetes

Once the patient was properly diagnosed, a continuous glucose monitor (CGM) became her most valuable tool. A CGM is a small device worn on the skin that measures blood sugar levels throughout the day and night, providing real-time feedback about how food, activity, and insulin affect glucose levels. For someone newly diagnosed with type 1 diabetes, a CGM serves as an educational tool that helps patients understand their condition and learn how to dose insulin appropriately .

The emergency department had prescribed a CGM, but the patient hadn't been able to pick it up initially. Once she received it, Dr. Peters used it to teach her how to adjust her insulin doses based on her actual glucose patterns. Interestingly, many adults with new-onset type 1 diabetes don't need as much insulin early on as expected. This patient didn't require rapid-acting insulin for meals at all, only the long-acting basal insulin. Working with a dietitian, she learned how to eat appropriately for type 1 diabetes and has become, as Dr. Peters noted, "a very good pupil of diabetes" .
Dr. Peters

The key lesson from this case is that type 1 diabetes in young, lean adults is a commonly missed diagnosis. Emergency departments and primary care providers need to expand their thinking beyond the stereotype that type 1 diabetes only occurs in children and type 2 in adults. By recognizing the clinical red flags, testing for islet autoantibodies in appropriate patients, and ensuring rapid referral to a diabetes specialist, doctors can catch type 1 diabetes earlier and help patients avoid the trauma and danger of diabetic ketoacidosis .

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