The 1 hour Oral Glucose Tolerance Test
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1 hour OGTT
The Sweet Success Program of California recommends that all pregnant women be screened for gestational
diabetes at 24-28 weeks, or earlier if risk factors are present. Screening is usually done using the 1 hour oral glucose tolerance test.
Patients should be screened at their first prenatal visit if any of the
following risk factors are present:
- Family history of diabetes in first-degree relatives
- Previous history of:
- Gestational diabetes
- Malformed infant
- >25 years of age
- BMI >30
- Glucosuria > 2+
- Member of an ethnic/racial group with a high prevalence of
(i.e., Hispanic-American, Native American, Asian-American, African-American, Pacific Islander, or of Indigenous Australian ancestry)
- Taking medications causing hyperglycemia (i.e. terbutaline,prednisone)
A plasma concentration >200 mg/dl (11.1
mmol/l) under any conditions outside of the context of a formal glucose
challenge test or a fasting plasma glucose concentration >126
mg/dl (7.0 mmol/l) warrants confirmatory testing as quickly as possible.
1 hour Oral Glucose Tolerance Test (OGTT)
The test can be done at any time of the day. Fasting is not required.
Administer a 50 gram glucose load followed by a one-hour plasma glucose:
- Negative test if : < 140 mg/dl
- Positive test if: > 140 mg/dl
- Values 140 mg/dl to 179 mg/dl require follow-up with a 3-hour
100 gram oral glucose tolerance test (OGTT) within one week.
- If the patient has a screening value >
180 mg/dl, a fasting blood
sugar should be checked as soon as possible.
- An elevated fasting value of > 95 and screening test
> 180 mg/dl provides two abnormal values, and treatment for gestational diabetes is recommended.
- If the fasting value is less than 95 then proceed with the 3 hour OGTT.
Women who were evaluated early during their pregnancy and found to be
normoglycemic should have screening repeated at 24 to 28 weeks.
*Guidelines for Care, California Diabetes and
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