How type 1 diabetes is diagnosed

A type 1 diabetes (T1D) diagnosis can happen suddenly and unexpectedly. Many times, particularly in children, the disease might first appear to be like a bad cold or flu. And many adults don’t know that T1D can be developed in adulthood, so they nor their healthcare providers will immediately consider T1D as a possibility when exhibiting symptoms.

What are the signs and symptoms of type 1 diabetes:

T1D is often first identified in children and adults as they show signs of the following symptoms:

  • Frequent urination
  • Increased thirst
  • Dry mouth
  • Drowsiness and lethargy
  • Itchy skin
  • Increased appetite
  • Fruity odour on breath
  • Blurred vision
  • Weight loss
  • Laboured breathing
  • Yeast infections

T1D often initially presents itself with the above symptoms, but it can only be properly identified through a series of tests. It’s important for healthcare providers to be aware of the signs and symptoms of T1D, as often people are only diagnosed at the point of diabetic ketoacidosis or DKA. DKA is a serious life-threatening condition that needs immediate treatment. Ketones and glucose can rise to very high levels in the blood, causing fluid loss and potentially organ failure.

The importance of screening

General population screening offers the potential to identify people who have early-stage, pre-symptomatic T1D. Canada has one of the fastest growing rates of T1D diagnoses anywhere in the world – and we don’t know why.

In 2023, JDRF Canada, in collaboration with CIHR, announced the recipients of the CIHR-JDRF Type 1 Diabetes Screening Research Consortium. This $12 million grant will develop a single nationally coordinated research network to explore key research questions about the feasibility and acceptability of general population screening for early-stage T1D in Canada. The consortium will build on experiences from other countries with T1D screening programs including the US, UK, Israel, Australia, and multiple European countries.

Learn more:

How is type 1 diabetes (T1D) diagnosed?

Fasting blood-glucose test
Doctors will often recommend a fasting blood-glucose test when they suspect T1D in a patient. This is a small sample blood test typically conducted in the morning after fasting overnight. The fasting helps give doctors a clear look at how the body manages blood glucose levels without the impact of food intake.

Oral glucose tolerance test
The oral glucose test takes the fasting test one step further. After fasting and having an initial blood test, people drink a highly sugary drink and then have their blood glucose levels tested over the course of approximately two hours. This shows the benchmark glucose levels without outside food or drink, or activity influences and later measures how the body responds to carbohydrate (sugar) intake.

Random blood-glucose test
The quickest option for testing for T1D is a random glucose test. This test simply measures a patient’s current blood glucose regardless of when and what they most recently ate. On occasion, this will be the first test, and then doctors will elevate to tests noted above as needed.

Glycated hemoglobin (HbA1c) test
The most comprehensive test is the hemoglobin A1c test. This blood test shows the average blood glucose level of the individual for their past two or three months.

Less common T1D tests
Some doctors may employ the following tests to find markers of T1D to ensure the optimal treatment plan.

This test measures how much C-peptide is in a person’s blood. Peptide levels typically mirror insulin levels in the body. Low levels of C-peptide and insulin can point to T1D.

Insulin Autoantibodies (IAA)
This tests looks for the antibodies targeting insulin.

Insulinoma-Associated-2 Autoantibodies (IA-2A)
This test looks for antibodies mounted against a specific enzyme in beta cells. Both the IA-2A and GADA tests are common T1D antibody tests.

Zinc Transporter 8 (ZnT8Ab)
This test looks at antibodies targeting an enzyme that is specific to beta cells.

Islet Cell Cytoplasmic Autoantibodies (ICA)
Islet cells are clusters of cells in the pancreas that produce hormones, including insulin. This test identifies a type of islet cell antibodies present in up to 80 percent of people with T1D.

Glutamic Acid Decarboxylase Autoantibodies (GADA or Anti-GAD)
This test looks for antibodies built against a specific enzyme in the insulin-producing pancreatic beta cells.

The honeymoon phase of type 1 diabetes
The onset of symptomatic diabetes doesn’t always happen all at once. During what is known as the “honeymoon phase,” people with T1D can experience a period in which they are asymptomatic. The honeymoon phase typically lasts a few months to a year post-diagnosis as, with the help of some injected insulin, a patient’s existing beta cells continue to function normally and produce enough insulin for blood glucose management.

Eventually, the majority of the insulin-producing beta cells in the pancreas cease functioning and the diabetes symptoms return. At this point, exogenous (external) insulin will be needed daily, either by multiple daily injections, pen or insulin pump.


The honeymoon phase and treatment

No matter how good A1C or blood glucose tests are during the honeymoon phase, the disease is still present and killing beta cells in the pancreas responsible for producing insulin. During this phase, healthcare providers will work with the individual or family to help maintain blood glucose levels with low-dose insulin treatments. Eventually, the remaining healthy cells will die off and insulin dosages will need to be increased.

T1D is fairly predictable with regard to endocrine system function during the honeymoon phase, but every case varies just a bit. Paying close attention to the body’s responsiveness to insulin therapy paired with regular blood glucose testing is paramount to successful management.

Slowing the autoimmune progress of type 1 diabetes

JDRF is currently funding research, some of which is in the clinical trial stage for drug therapies that can slow or potentially halt the autoimmune process during the honeymoon stage of T1D. One of these therapies, Tzield has been approved for use in the USA.

In a JDRF-funded clinical trial, baricitinib—a small molecule immune therapy that blocks Janus Kinase, which is critical to signaling pathways within both immune cells and beta cells in T1D—preserved beta cell function in the disease.

Additionally, ustekinumab, in another JDRF-funded trial currently recruiting in Canada, is helping JDRF address the autoimmunity behind T1D.

Ultimately, the hope is that T1D screening will be a pathway to a cure, catching the disease and treating it before it can start.