Glucose Tolerance Test, Oral
(OGTT)

Sample type

Serum gel or plasma EDTA

Uses

Check for prediabetes and diabetes.

Check pregnant women for gestational diabetes.

Precautions

Tell your doctor about all the prescription and non-prescription medicines you are taking. You may be told to stop taking certain medicines before the test.

Do not eat, drink, smoke, or do strenuous exercise for at least 8 hours before your first blood sample is taken. (You can drink water before the test.)

Interfering factor

. There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Pre-analytical errors

The corrective action

The sample must be rejected and another sample be obtained.

Post-analytical errors

reports were sent to the incorrect patient

If the patient’s gender is written wrong in the report, the reference range was written incorrectly

The corrective action

communication with patient, apologising for the error, and providing him with the correct report

If the report is not delivered to the patient and this error is discovered, fix it, but if the report is delivered to the patient, apologise to him, tell him that an error has occurred, and replace it with the correct report. And next time, be careful when you write down the gender and reference range

Reference range

Results of the oral glucose tolerance test are given in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).

Type 2 diabetes

If you’re being tested for type 2 diabetes, two hours after drinking the glucose solution:

A normal blood glucose level is lower than 140 mg/dL (7.8 mmol/L).

A blood glucose level between 140 and 199 mg/dL (7.8 and 11 mmol/L) is considered impaired glucose tolerance, or prediabetes. If you have prediabetes, you’re at risk of eventually developing type 2 diabetes. You’re also at risk of developing heart disease, even if you don’t develop diabetes.

A blood glucose level of 200 mg/dL (11.1 mmol/L) or higher may indicate diabetes.

If the results of your glucose tolerance test indicate type 2 diabetes, your doctor may repeat the test on another day or use another blood test to confirm the diagnosis. Various factors can affect the accuracy of the glucose