How is type 1 diabetes (T1D) diagnosed?

T1D often initially presents itself as the flu or malaise, but physicians must be quick to spot the telltale signs of a possible T1D diagnosis and order additional tests.

Fasting blood-glucose test

Doctors will often recommend a fasting blood-glucose test when they suspect T1D may be present. 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-sugar 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 sugary drink and then have their blood sugar tested over the course of approximately two hours. This shows the benchmark sugar without outside 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 sugar regardless of when and what he or she ate most recently. 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-sugar level for the past two or three months.

The honeymoon phase

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.

The honeymoon phase and treatment

No matter how good A1C or blood-sugar tests are during the honeymoon phase, the disease is still present and killing beta cells. During this phase, physicians will help maintain blood-glucose management with low-dose insulin treatments. Eventually, the remaining healthy cells will die off and insulin dosages will need to be increased.

What it means for people with T1D

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-sugar testing is paramount to successful management.

Less common T1D tests

Because each case can be as unique as the individual, some doctors may employ the following tests to find markers of T1D to ensure the optimal treatment plan:

• C-Peptide
  While most tests check for antibodies, 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.

How age affects a T1D diagnosis

There are some side effects in the overall health of a person with T1D that present themselves in time. Diabetic eye disease and kidney, nerve, or circulation damage can appear in people who have had T1D for 15 years or more. With proper maintenance and routine checkups, these effects can often be limited or avoided altogether.