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Glucose (50 g oral glucose tolerance test) – Serum

Published: August 9, 2026Updated: August 16, 2026

This test measures your blood sugar levels before and after drinking a sugary liquid to check how your body processes glucose over time.

Quick summary

["Assesses how well your body manages blood sugar after eating sugar."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
25680-0
Short code
Glucose pre 50 g Glc PO SerPl-sCnc
Synonyms
Glucose pre 50 g Glc PO SerPl-sCnc
Category
glucose
Sample
serum
Container
Red-top tube (SST)
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
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may recommend an oral glucose tolerance test if you have symptoms like frequent urination, unexplained weight changes, fatigue, or if you have risk factors for diabetes, such as a family history or obesity. It helps diagnose conditions like diabetes, prediabetes, or gestational diabetes during pregnancy.

What to Expect During the Test

You’ll drink a sweet liquid (about 75 grams of glucose) and have blood drawn from your arm at set intervals (usually before drinking and 1 to 2 hours afterward) to check your blood sugar levels.

Preparation Tips

Follow your doctor’s instructions carefully. Avoid sugary foods or drinks for 3 days before the test, and don’t smoke or exercise heavily on the day of testing.

What the Results Mean

Results help determine if your blood sugar is consistently high or low after consuming glucose, which can indicate how your body handles sugar. Your doctor will interpret the results in relation to your symptoms and medical history.

Reference range

Fasting: 70-100 mg/dLN/A

Specimen: serum

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.

Clinical Significance

Short name

Oral Glucose Tolerance Test (OGTT) – Serum Glucose

Frequently asked questions

How long does it take to get results from this test?
Results are typically available within 1 to 3 business days, depending on your lab. Your healthcare provider will discuss them with you during your follow-up visit.
Can I eat or drink anything before the test?
No, you should fast for 8 to 12 hours before the test, except for water. Avoid sugary foods or drinks for 3 days beforehand to ensure accurate results.
Is there any risk or discomfort with this test?
There’s minimal discomfort—just a few blood draws. Rarely, you might feel slight pain or bruising at the needle site, but it’s usually mild and temporary.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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