Skip to content

Oral Glucose Tolerance Test (OGTT) – 2-Hour Plasma Glucose

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

This test measures your blood sugar levels after drinking a sugary liquid to check how your body processes glucose over time. It helps diagnose conditions like diabetes or identify prediabetes.

Quick summary

["Assesses how your body handles glucose, aiding diabetes risk assessment."]

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

Key facts at a glance

LOINC
68558-6
Short code
OBGYN D/C sum
Synonyms
OBGYN D/C sum
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
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 It’s Done

Your doctor may recommend this test if you have symptoms of high blood sugar (like frequent urination, extreme thirst, or unexplained weight loss), a family history of diabetes, or if you’re overweight. It’s also used during pregnancy (gestational diabetes screening) or if you have other health concerns like high blood pressure or heart disease.

What to Expect

You’ll drink a sugary liquid (about 8 oz) while sitting quietly. Blood is drawn from your arm twice: once before drinking and again 2 hours later. The test is quick but requires resting during the 2-hour wait.

Preparation

Follow your doctor’s instructions carefully. Avoid sugary foods/drinks for 3 days before the test, and don’t smoke or exercise intensely 24 hours beforehand. If you’re pregnant, inform your doctor about any medications you’re taking.

What the Results Mean

Results help determine if your body can control blood sugar normally. Abnormal results may prompt further testing or lifestyle changes, such as diet, exercise, or medication.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

OGTT (2-hour)

Frequently asked questions

What does a high or low result indicate?
High levels after drinking sugary liquid may signal diabetes or insulin resistance. Low levels (rare) could indicate severe insulin deficiency or other metabolic issues. Your doctor will interpret results in the context of your overall health.
How often should I get this test?
Typically recommended every 1–3 years if you have no diabetes risk factors. Those with prediabetes or diabetes may need more frequent checks. Always follow your doctor’s schedule.
Can I eat or drink anything before the test?
No—fasting is required. Avoid food, beverages (except water), caffeine, or smoking for 8 hours before the test. Check with your doctor if you have questions about specific medications.
  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