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Oral Glucose Tolerance Test (OGTT) with Serum Samples Collected During the Test

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

This test measures how your body processes glucose (sugar) over time, typically after drinking a sugary liquid. It helps check for diabetes or prediabetes.

Quick summary

["Assesses blood sugar control and identifies diabetes risk or existing conditions."]

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

Key facts at a glance

LOINC
83588-4
Short code
OBGYN Nurse OP Note
Synonyms
OBGYN Nurse OP Note
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
obstetrics-and-gynecology-nurse
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

What to Expect Before the Test

You’ll start by drinking a sugary liquid (usually 75 grams of glucose dissolved in water). Blood samples are taken from your arm at specific intervals—often before drinking, 30 minutes, 60 minutes, and then every hour for 2 hours. This helps track how your body handles glucose.

Why This Test Matters

An OGTT helps doctors diagnose diabetes, gestational diabetes (in pregnant women), or prediabetes. It also evaluates how well your pancreas produces insulin to manage blood sugar levels.

How the Test Works

Your blood is drawn to measure glucose levels at different times. If your blood sugar rises too quickly or stays high, it may indicate diabetes or insulin resistance.

Common Reasons for Testing

Doctors may recommend an OGTT if you have symptoms like excessive thirst, frequent urination, unexplained weight loss, or fatigue. It’s also used for pregnant women with risk factors or those with a family history of diabetes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

OGTT

Frequently asked questions

How long does the test take?
The test itself takes about 3 hours, including preparation and follow-up blood draws. You’ll need to stay seated or lie down during the process.
Can I eat or drink anything before the test?
No, you’ll need to fast for 8–12 hours before drinking the sugary liquid. Avoid caffeine, alcohol, or sugary foods/snacks during this time.
Will I feel any discomfort?
You may feel a slight pinch when blood is drawn, but the test itself is painless. Some people experience mild nausea or dizziness after drinking the sugary liquid, but this usually passes quickly.
  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