Diabetes Tests & Diagnosis

Diabetes diagnosis: tests used to detect diabetes.

There are several different tests used to diagnose diabetes. When testing for diabetes, if you test high on any test, the same test should be completed again on another day to diagnose diabetes accurately.

Testing for diabetes should always be done in your doctor’s office, lab, or other healthcare settings. Home glucometers can be purchased at any pharmacy or discount store without a prescription. However, if you suspect diabetes, it is essential that you visit your doctor rather than trying to self-diagnose.

Types of Diabetes

Type 1 Diabetes and LADA

Type 1 diabetes and LADA (latent autoimmune diabetes in adults, sometimes referred to as type 1.5 diabetes) are autoimmune conditions in which your immune system attacks and destroys the beta cells in your pancreas that produce insulin. Type 1 diabetes is very progressive, whereas LADA is a much slower progressing condition.

Prediabetes & Type 2 Diabetes

Prediabetes, if not treated, becomes type 2 diabetes. Prediabetes is a condition in which your blood sugar (glucose) levels are higher than normal. If action isn’t taken, prediabetes turns into type 2 diabetes because of insulin resistance.

Gestational Diabetes

Gestational diabetes is diagnosed for the first time while pregnant. It causes high blood sugar that can potentially negatively affect your pregnancy and your baby’s health.

Tests for Type 1 Diabetes, LADA, Prediabetes, and Type 2 Diabetes

Glycated Hemoglobin (HbA1c or A1c) Test

An HbA1c test measures your average blood sugar levels over the past two to three months through a blood draw. This test should be completed in the morning after an 8 hour fast for best results. This test can be inaccurate for people who have anemia. For someone who hasn’t been diagnosed with diabetes, an HbA1c below 5.7% is normal, and a range of 5.7% to 6.4% indicates you have prediabetes. An HbA1c of 6.5% or higher indicates diabetes.

Fasting Blood Sugar Test

A fasting blood sugar test, also called a fasting plasma glucose (FPG), measures your blood sugar after an overnight fast. A fasting blood sugar level of 99 mg/dL or lower is normal. A level between 100 to 125 mg/dL indicates prediabetes. A level of 126 mg/dL or higher indicates diabetes.

Oral Glucose Tolerance Test

An oral glucose tolerance test measures your fasting blood sugar before and after consuming a sugary drink. On the morning following an overnight fast, your blood sugar level is measured. You will then drink the liquid and wait for 1 to 3 hours after finishing the drink. At 2 hours after finishing the drink, a blood sugar level of 140 mg/dL or lower is considered normal. A level between the range of 140 mg/dL to 199 mg/dL indicates prediabetes. A level of 200 mg/dL or higher indicates diabetes.

Random Blood Sugar Test

A random blood sugar test is just that, a random test of your blood that measures your blood sugar level. You do not need to fast for this test. A blood sugar level of 200 mg/dL or above indicates that you have diabetes. This test is not used to determine prediabetes but rather whether or not you have diabetes.

Pancreatic Autoantibody Test (Islet Autoantibody Test)

A pancreatic autoantibody test is a blood test that tests for the four common antibodies that attack the beta cells in your pancreas. This test is often used to determine if a person has LADA versus type 2 diabetes. The results of this test vary depending on the type of diabetes you have, as follows:

  • Type 1 diabetes – positive test result, typically positive to all four antibodies
  • Type 2 diabetes – negative test result
  • LADA – positive test result, typically positive for 1-4 antibodies

C-Peptide Test

The C-peptide test measures the level of C-peptide in your blood or urine. C-peptide is made in the pancreas along with insulin. Insulin and c-peptide are released from the pancreas at the same time and in equal amounts. So, a C-peptide test shows how much insulin your body is making. The C-peptide test is another useful test to determine if you have LADA instead of type 2 diabetes. The results of this test also vary depending on the type of diabetes you have:

  • Type 1 diabetes – Very low
  • Type 2 diabetes – Normal to high
  • LADA – Low

Ketone Test

While a ketone test does not tell if you have diabetes, testing for ketones is often done in conjunction with other blood tests to rule out diabetic ketoacidosis (DKA), which can be deadly if not addressed. A ketone test is done by testing your blood or urine. Ketones are the byproduct of your body burning fat for fuel instead of sugar (glucose). When ketone levels are high along with high blood sugar levels, diabetic ketoacidosis can occur.

HbA1c Fasting Blood Sugar Glucose Tolerance Random Blood Sugar
Below 5.7%
99 mg/dL or below
140 mg/dL or below
5.7 - 6.4%
100 - 125 mg/dL
140 - 199 mg/dL
6.5% or above
126 mg/dL or above
200 mg/dL or above
200 mg/dL or above

Tests for Gestational Diabetes

Glucose Screening Test

A glucose screening test is a test to establish a baseline blood sugar level, which is done one hour after drinking a sugary drink. A normal blood sugar result for this initial test is 140 mg/dL or lower. If your level is higher than 140 mg/dL, you will need a glucose tolerance test.

Glucose Tolerance Testing

A glucose tolerance test is a test to measure your blood sugar level after consuming a sugary drink. This test is done after fasting overnight. Typically your blood will be drawn before consuming the sugar drink and then taken at 1, 2, and 3 hours after finishing the drink. Usually, if your blood sugar is too high on two or more readings, you have gestational diabetes.

I’ve Been Diagnosed With Diabetes, Now What?

If you have been diagnosed with any type of diabetes, let us help you on your journey. Our website is filled with educational science-based articles to help you learn about diabetes. Also, check out our recipe database, full of delicious and healthy diabetes-friendly recipes your whole family will enjoy.

If you have prediabetes or type 2 diabetes, it may be possible to reverse your diabetes so that you maintain healthy blood sugar levels without needing diabetes medications. Use our free Diabetes Wellness Plan to get started.