A glucose test is done for various reasons depending on the context, including diagnosing or monitoring diabetes, screening for gestational diabetes during pregnancy, and checking for prediabetes.
When a glucose test is done:
- Fasting blood glucose test: After fasting (not eating or drinking anything but water) for at least 8 hours. Used to screen or monitor diabetes or prediabetes.
- Random blood glucose test: Can be done any time, even after eating, often used if diabetes symptoms are present.
- Glucose challenge test (during pregnancy): Typically done between 24 and 28 weeks of pregnancy to screen for gestational diabetes without fasting. It involves drinking a glucose drink and testing blood sugar 1 hour later.
- Oral glucose tolerance test (OGTT): Requires fasting, involves drinking a glucose solution and testing blood sugar multiple times over 2-3 hours. Used to diagnose gestational diabetes or confirm diabetes/prediabetes.
- For diabetes management: Frequent testing may be recommended depending on diabetes type and treatment plan.
Summary by situation:
Test Type| When to Do It| Purpose
---|---|---
Fasting glucose| After at least 8 hours fasting| Screening/monitoring diabetes
or prediabetes
Random glucose| Any time, especially with symptoms| Immediate check for
diabetes
Glucose challenge (pregnancy)| 24-28 weeks pregnant, non-fasting| Screen for
gestational diabetes
OGTT| After fasting, multiple blood samples in 2-3 hours| Diagnose diabetes or
gestational diabetes
Self-monitoring| Multiple times daily for type 1 or insulin-use type 2
diabetes| Manage blood glucose levels
Pregnant women typically have glucose screening between 24 and 28 weeks, sometimes earlier if high risk. People with type 1 diabetes may test several times a day, especially around meals, exercise, or when sick.
