8-Hour Oral Glucose Tolerance Test (8-hour Serum Glucose)
This test measures your blood sugar level 8 hours after drinking a sugary liquid. It helps assess how well your body manages glucose over time, often used to evaluate diabetes or prediabetes.
["This test helps doctors check long-term blood sugar control beyond just a single reading."]
Key facts at a glance
- LOINC
- 21306-6
- Short code
- Glucose 8h Ur-mRate
- Synonyms
- Glucose 8h Ur-mRate
- Category
- glucose
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Ref low
- 70
- Ref high
- 100
- Critical range
- 50 N/A – 400 N/A
- Fasting
- true
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82947
- SNOMED
- 260395008
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your doctor may recommend this test if you have symptoms of diabetes (like frequent urination, extreme thirst, or unexplained weight changes) or if you have risk factors such as obesity, high blood pressure, or a family history of diabetes. It’s also used to monitor glucose levels in people with known diabetes to ensure proper management.
How the Test Works
You’ll drink a sugary liquid (usually glucose solution) while fasting. Blood is drawn from a vein in your arm at baseline and then again 8 hours later to measure your glucose level. This helps determine how your body processes glucose over an extended period.
Sample Collection
A healthcare provider will insert a small needle into your arm to collect blood. You may feel a slight pinch, but it’s usually over quickly. The blood is sent to a lab for testing.
What to Expect Before the Test
You’ll need to fast (not eat or drink anything except water) for about 12 hours before the test. Avoid caffeine, alcohol, and smoking on the day of the test. Let your doctor know about any medications you’re taking, as some may affect results.
Reference range
Fasting: 70-100 mg/dLN/A
Fasting for 8-12 hours required. Water is permitted. Avoid chewing gum and smoking before the test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
8-hour glucose
Frequently asked questions
What does an abnormal result mean?
Can I eat or drink anything before the test?
How long will I need to prepare for this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy