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Glucose, 5-Gram Glucose Tolerance Test (Oral)

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

This test measures how your body processes glucose (sugar) after drinking a sugary liquid. It helps check for diabetes or how well your pancreas produces insulin.

Quick summary

["Assesses blood sugar control and diabetes risk after eating sugar."]

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

Key facts at a glance

LOINC
1548-7
Short code
Glucose pre .5 g/kg Glc IV SerPl-mCnc
Synonyms
Glucose pre .5 g/kg Glc IV SerPl-mCnc
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

What to Expect Before the Test

You’ll drink a sweet liquid containing 5 grams of glucose (about 150–200 calories). Blood samples are taken at baseline and 1–2 hours later to check glucose levels. Wear loose clothing and plan for a few hours of rest.

How the Test Works

Your blood sugar is measured before drinking the glucose solution and again after drinking it. The test evaluates how your body responds to sugar over time, helping doctors diagnose conditions like diabetes or gestational diabetes.

Why It’s Done

Doctors may recommend this test if you have symptoms like frequent urination, extreme thirst, unexplained weight loss, or fatigue. It’s also used for screening pregnant women or those with risk factors for diabetes.

What to Prepare

Avoid caffeine, alcohol, or sugary foods/drinks 24 hours before the test. Wear comfortable clothing and bring identification if you have diabetes or take diabetes medications.

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.

This test helps identify diabetes or prediabetes by measuring how your body manages glucose. Abnormally high or low results may indicate insulin resistance, gestational diabetes, or other metabolic conditions requiring further evaluation.

Short name

Oral Glucose Tolerance Test (OGTT)

Frequently asked questions

How long does the test take?
The test itself takes about 1–2 hours, including blood draws. You’ll need to stay for the full duration to ensure accurate results.
Can I eat or drink anything before the test?
No, avoid food and liquids (except water) for 8–12 hours before the test. Follow your doctor’s specific instructions to get the most accurate results.
Will I feel any pain or discomfort?
You may feel a slight pinch when blood is drawn, but it’s usually brief. The test itself involves drinking a sugary liquid, which may cause temporary nausea or thirst.
  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