How to Test for Diabetes Type


Whether warning signs of diabetes are present or not, there are various tests that are performed to evaluate a person’s risk of developing certain types of diabetes or make a diabetes diagnosis.

Learn more about what tests are out there:

Oral Glucose Tolerance Test (OGTT)

Tests for: PrediabetesType 2Gestational diabetes

This blood test requires fasting for eight hours. After blood is drawn, a glucose drink is administered and blood is drawn again after one or more hours.

If the results of the OGTT are higher than what is considered normal but not quite high enough for a diagnosis of diabetes, the blood sugar level may fall into the category of prediabetes,.

Prediabetes, history of gestational diabetes, being overweight, poor nutrition, ethnicity and family history of diabetes put pregnant women at an increased risk of developing gestational diabetes.

Glucose Challenge Test

Tests for: Gestational diabetes

Various versions of the OGTT, the glucose challenge test is also used to determine whether expecting mothers have gestational diabetes. The test is usually directed at women who are 24 – 28 weeks pregnant., but often earlier if a person is considered to be at high risk.

Blood is drawn 1 or more hours after a glucose drink is administered—no fasting is required. The results will determine whether diabetes is present and if further testing is necessary.

Plasma Glucose Tests

Test for: Type 1Type 2

Fasting Plasma Glucose (FPG): An FPG is a snapshot measure of blood sugar levels. This blood test is usually performed first thing in the morning after fasting for eight hours.

Random Plasma Glucose (RPG): No fasting is required for this blood test.

Hemoglobin A1c (HbA1c) Test

Tests for: Type 1Type 2

Most people with diabetes are familiar with this test—it’s usually administered at endocrinologist check-ups. Also called the glycated hemoglobin test and glycohemoglobin, hemoglobin A1c measures average glucose over a three-month span. It’s a simple blood test that examines the amount of glucose bound to red blood cells. People without diabetes usually have A1c levels between 4% and 6%. A diabetes diagnosis can result from an A1c of 6.5% or higher. Prediabetes is a level between 5.7-6.4.

Check out our secrets to lowering your A1c from a diabetic health coach!

Autoantibodies Tests

Tests for: Type 1

TrialNet is an international research network that screens participants for the presence of specific autoantibodies, which our bodies create to act against enzymes involved in insulin production. These tests can detect autoantibodies years before a type 1 diagnosis is made.

The presence of these autoantibodies, and whether they are alone or accompanied by another, can indicate the likelihood of a person developing type 1 (one reason why the TrialNet focus lies on first-degree relatives of people who have already been diagnosed with type 1). The list includes: GAD65/GAD65H, called GAD or pancreatic islet cell autoantibodies; ICA512, called ICA or islet cell autoantibodies; Islet Antigen 2, called IA-2 or Tyrosine phosphatase-related islet antigen; Insulin Auto-Antibody (IAA); ZNT8A, a zinc transporter.

A doctor may also order blood tests for the presence of autoantibodies.

Genetic Testing

Tests for: Type 1Type 2

According to Genetics Home Reference, the presence of certain variants of the HLA-DQA1HLA-DQB1, and HLA-DRB1 genes indicate an increased risk of developing type 1 diabetes. This family of genes works to identify the proteins made by the body and proteins from the outside. The following genes are examples of those involved in those processes: CCR5, , HLA-DQB1, HNF1A, IL2RA, ITPR3, OAS1, PTPN22, SUMO4.

Although over 65 genetic variants are known to increase the risk of type 2 diabetes (Lyssenko, Laakso), more research needs to be done to develop screening.

C-Peptide Test

Tests for: Type 1Type 2

Normal levels of C-Peptide are associated with normal insulin production. A blood test examining a person’s C-Peptide levels can indicate how much insulin is present in the body. It can help identify type 1 or type 2 diabetes, although many people with type 1 still produce some insulin thus still have +c-peptide.



Genetic Screening for the Risk of Type 2 Diabetes. Valeriya Lyssenko, Markku Laakso. Diabetes Care Aug 2013, 36 (Supplement 2) S120-S126; DOI: 10.2337/dcS13-2009

Genetics Home Reference: Type 1 diabetes

JDRF: The Complexity of Diagnosing Type 1 Diabetes

Joslin Diabetes Center: Diagnosing Impaired Glucose Tolerance (IGT)

NIH: Tests & Diagnoses for Gestational Diabetes

TrialNet: Waiting for My Results

WebMD: Diabetes Testing

WebMD: Do I need an Oral Glucose Tolerance Test?

Learn about the different forms of diabetes.

WRITTEN BY BT1 Editorial Team, POSTED 12/14/17, UPDATED 12/30/22

This piece was authored collaboratively by the Beyond Type 1 Editorial Team.