Can this result diagnose a condition on its own?

No. Laboratory results are interpreted with symptoms, medical history, sampling conditions, and related tests.

Which reference range or cutoff should I use?

Start with the performing laboratory's report and the purpose of testing; diagnostic cutoffs are separate sourced clinical thresholds.

When should I discuss the result with a healthcare professional?

Results that are clearly outside range, persistent, symptomatic, or unexpected should be reviewed by a healthcare professional.

Information about a laboratory test

OGTT in Pregnancy: What Is the Glucose Tolerance Test?

In pregnancy, the OGTT is used to evaluate gestational diabetes; the protocol and cutoffs can differ from nonpregnant testing.

Test summary

Test name: OGTT
Abbreviations: OGTT, GTT
Category: Endocrinology / Glucose Metabolism
Panel: Diabetes / Glucose Tolerance
Specimen: Plasma / serum
Common units: mg/dL, mmol/L

What does the test measure?

Measures the blood-glucose response before and after drinking a defined glucose load.

Why is the test ordered?

Can be used to evaluate prediabetes, type 2 diabetes, and gestational diabetes.

Information about a low result

A low post-load glucose result depends on timing, symptoms, and clinical context and is not diagnostic by itself.

Information about a high result

A high post-load glucose result can occur when the body has impaired handling of a glucose load.

Reference and clinical context

Pregnancy glucose-screening and OGTT protocols vary by setting and guideline. Do not apply a single cutoff without knowing the protocol and gestational timing.

Reference context 1

<= 139 mg/dL

Population: Nonpregnant adults
Pregnancy status: No
Specimen: Plasma

Normal 2-hour OGTT context

The source uses <=139 mg/dL as the threshold for this context. Individual risk and laboratory context still matter.

Reference context 2

>= 140 – <= 199 mg/dL

Population: Nonpregnant adults
Pregnancy status: No
Specimen: Plasma

Impaired glucose tolerance / prediabetes

This sourced diagnostic threshold of >=140–<=199 mg/dL applies to nonpregnant testing; confirmation is usually required when classic symptoms are absent.

Reference context 3

>= 200 mg/dL

Population: Nonpregnant adults
Pregnancy status: No
Specimen: Plasma

Diabetes diagnostic threshold

This sourced diagnostic threshold of >=200 mg/dL applies to nonpregnant testing; confirmation is usually required when classic symptoms are absent.

Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.

Interpretation notes

Pregnancy OGTT protocols and cutoffs can differ from nonpregnant diagnostic testing; the exact protocol must be known.

Related specialties

Endocrinology
Internal Medicine
Family Medicine
Pediatric Endocrinology

Frequently asked questions

Sources

Diabetes Tests & Diagnosis — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
U.S. government medical reference · 2026 · Fasting plasma glucose, A1C, OGTT, random glucose; diagnostic thresholds and pregnancy caveats · Verified: Aug 12, 2026
Tests & Diagnosis for Gestational Diabetes — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
U.S. government medical reference · 2026 · Glucose challenge and OGTT in pregnancy; protocol-specific interpretation · Verified: Aug 12, 2026