Prediabetes diagnosis

Blood tests are used to diagnose prediabetes as well as diabetes. Regular glucose screenings can help monitor your condition and is especially important if you are overweight or have additional risk factors for prediabetes or type 2 diabetes.

There are several blood tests used to diagnose prediabetes²⁹:

• A1C (glycated hemoglobin) test: This test indicates your average blood sugar level by measuring the percentage of blood sugar attached to your hemoglobin (the oxygen-carrying protein found in red blood cells) over the past 3 months. In general, an A1C level of 5.7%–6.4% indicates prediabetes. Certain conditions, however, can make A1C tests inaccurate, such as if you are pregnant³⁰ (A1C levels can be falsely low in the 2nd trimester, but may rise in the 3rd trimester).
• Fasting blood sugar test: This test, which measures blood sugar levels in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L), involves a blood sample being taken after you fast for at least 8 hours or overnight. Generally, a fasting blood sugar level³¹ from 100–125 mg/dL (5.6–6.9 mmol/L) is considered prediabetes.
• Oral glucose tolerance test³²: This test can be used as a screening tool to help diagnose Type 2 diabetes, but is most commonly used in diagnosing diabetes in pregnancy (gestational diabetes). A blood sample is taken after fasting for at least 8 hours or overnight. The patient is then given a sugary solution to drink, and blood sugar levels are generally drawn 1–3 hours later, as directed by your prescriber. In general, a blood sugar level from 140–199 mg/dL (7.8–11.0 mmol/L) is considered prediabetes. If you have prediabetes, you may need to undergo further testing³³.

At least once a year, your healthcare provider will likely check your:

• Fasting blood sugar
• Hemoglobin A1C
• Total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), and triglycerides

You may have to undergo testing more frequently if you have additional risk factors for developing diabetes.

Diagnosis of prediabetes in children

Type 2 diabetes is becoming more common in children and adolescents, likely due to rising rates of childhood obesity. Prediabetes testing for children³⁴ is recommended when a child is overweight or obese and has at least two other risk factors for type 2 diabetes. The risk factors for type 2 diabetes that are unique to children include low birth weight and being born to a mother who had gestational diabetes.

Type 2 diabetes is more common among girls than boys. A diagnosis of childhood type 2 diabetes often occurs during puberty but can occur as early as at age 10. This is in part because the hormones present during puberty make it harder for the body to use insulin, (especially in girls).

The ranges of blood sugar levels considered to be normal, prediabetic, and diabetic are the same for children and adults. Children diagnosed with prediabetes should be tested for type 2 diabetes at least once a year. Testing should occur more frequently if a child experiences changes in weight or develops signs and symptoms of diabetes, such as increased thirst, increased urination, fatigue, or blurred vision.