Main AHCA Website

AHCA’s main website for information on Medicaid, Health Quality Assurance and the Florida Center for Health Information and Transparency.

Go >

Florida Health Information Network

This website provides information and resources relating to AHCA’s initiatives for Health Information Technology and Health Information Exchange.

Go >

Provides health education and information to compare and locate health care providers in Florida to make well-informed health care decisions.

Go >
AHCA Network of Websites

Health Education

Health Encyclopedia

Search the Health Encyclopedia

Glucose tolerance test - non-pregnant


The glucose tolerance test is a lab test to check how your body breaks down sugar.

Tests to screen for diabetes during pregnancy are done differently.

Alternative Names

Oral glucose tolerance test - non-pregnant; OGTT - non-pregnant; Diabetes - glucose tolerance test

How the Test is Performed

The most common glucose tolerance test is the oral glucose tolerance test (OGTT).

Before the test begins, a sample of blood will be taken.

You will then be asked to drink a liquid containing a certain amount of glucose (usually 75 grams). Your blood will be taken again every 30 to 60 minutes after you drink the solution.

The test may take up to 3 hours.

A similar test is the intravenous (IV) glucose tolerance test (IGTT). It is rarely used, and is never used to diagnose diabetes. With IGTT, glucose is injected into your vein for 3 minutes. Blood insulin levels are measured before the injection, and again at 1 and 3 minutes after the injection. The timing may vary.

How to Prepare for the Test

Make sure you eat normally for several days before the test.

Do not eat or drink anything for at least 8 hours before the test. You cannot eat during the test.

Ask your health care provider if any of the medicines you take can affect the test results.

How the Test will Feel

Drinking the glucose solution is similar to drinking very sweet soda.

Serious side effects from this test are very uncommon. With the blood test, some people feel nauseated, sweaty, light-headed, or may even feel short of breath or faint after drinking the glucose. Tell your doctor if you have a history of these symptoms related to blood tests or medical procedures.

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

Glucose is the sugar the body uses for energy. People with untreated diabetes have high blood glucose levels.

Most often, the first tests used to diagnose diabetes in people who are not pregnant are:

  • Fasting blood glucose level: diabetes is diagnosed if it is higher than 126 mg/dL on 2 different tests
  • Hemoglobin A1c test: diabetes is diagnosed if the test result is 6.5% or higher

Glucose tolerance tests are also used to diagnose diabetes. The OGTT is used to screen for, or diagnose diabetes in people with a fasting blood glucose level that is high, but is not high enough (above 125 mg/dL) to meet the diagnosis for diabetes.

Normal Results

Normal blood values for a 75 gram OGTT used to check for type 2 diabetes in those who are not pregnant:

  • Fasting: 60 to 100 mg/dL
  • 1 hour: less than 200 mg/dL
  • 2 hours: less than 140 mg/dL

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

A glucose level that is higher than normal may mean you have pre-diabetes or diabetes:

  • A 2 hour value between 140 and 200 mg/dL is called impaired glucose tolerance. Your doctor may call this "pre-diabetes." It means you are at increased risk of developing diabetes over time.
  • A glucose level of 200 mg/dL or higher is used to diagnose diabetes.

Serious stress to the body, such as from trauma, stroke, heart attack, or surgery, can raise your blood glucose level. Vigorous exercise can lower your blood glucose level. 

Some medicines can raise or lower your blood glucose level. Before having the test, tell your provider about any medicines you are taking.


You may have some of the symptoms listed above under the heading titled "How the Test will Feel."

Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)


American Diabetes Association. Standards of medical care in diabetes -- 2015. Diabetes Care. 2015;38:S1-S76. PMID: 25537706

Pagana KD, Pagana TJ. Blood studies. Mosby's Manual of Diagnostic and Laboratory Tests. 5th ed. Philadelphia, PA: Elsevier Mosby; 2014:chap 2.

Review Date:7/24/2015
Reviewed By:Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997-A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.

Outcome Data

No data available for this condition/procedure.

Read More

Cushing syndrome

Diabetes *

Gestational diabetes

* Has Related Health Outcome Information

Health Encyclopedia

More Features

We Appreciate Your Feedback
1. Did you find this information useful?

2. Would you recommend this website to family and friends?