How The Test Is Performed
TWO-STEP TESTING
During the first step, you will have a glucose screening test:
- You do not need to prepare or change your diet in any way.
- You will be asked to drink a liquid that contains glucose.
- Your blood will be drawn 1 hour after you drink the glucose solution to check your blood glucose level.
If your blood glucose from the first step is too high, you will need to come back for a 3-hour glucose tolerance test. For this test:
- DO NOT eat or drink anything for 8 to 14 hours before your test.
- You will be asked to drink a liquid that contains glucose, 100 grams .
- You will have blood drawn before you drink the liquid, and again 3 more times every 60 minutes after you drink it. Each time, your blood glucose level will be checked.
- Allow at least 3 hours for this test.
ONE-STEP TESTING
You need to go to the lab one time for a 2-hour glucose tolerance test. For this test:
- DO NOT eat or drink anything for 8 to 14 hours before your test.
- You will be asked to drink a liquid that contains glucose .
- You will have blood drawn before you drink the liquid, and again 2 more times every 60 minutes after you drink it. Each time, your blood glucose level will be checked.
- Allow at least 2 hours for this test.
Group B Streptococcus Test
GBS is a healthy vaginal bacterium however, not all women will test positive. GBS does not usually pass to the baby, but if it does, it can cause serious illness. A vaginal-rectal swab will be done around 35-37 weeks to identify whether you have this bacteria present. If our laboratory identifies that the bacteria is present, you will be treated with antibiotics while in labour.
Oral Gtt In Pregnancy
Oral GTTs are commonly used to screen women for gestational diabetes. There is a strong correlation between increasing maternal glucose levels at 2432 weeks gestation and a range of adverse maternal and fetal outcomes. Several different strategies are used worldwide in the screening and diagnosis of gestational diabetes.
The American Diabetes Association offers two approaches to gestational diabetes screening a “one-step” approach with a single 2 hour 75 g OGTT, or a “two-step” approach with a 1 hour 50 g screening OGTT followed by a confirmatory 3 hour 100 g OGTT in patients who screen positive.
The Australian Diabetes in Pregnancy Society Consensus Guidelines for the Testing and Diagnosis of Gestational Diabetes Mellitus in Australia recommend early testing for gestational diabetes mellitus in women with risk factors, in a tiered approach to early glucose testing.
Moderate risk factors include the following:
-
Ethnicity: Asian, Indian subcontinent, Aboriginal, Torres Strait Islander, Pacific Islander, Maori, Middle Eastern, nonwhite African
-
Body mass index of 2535 kg/m2
High risk factors include the following:
-
Previous gestational diabetes mellitus
Contributor Information and Disclosures
Jiun-Lih Jerry Lin, MBBS, MS Clinical Associate Lecturer, MD Program Research Supervisor, Sydney Medical School, University of Sydney Orthopaedic Registrar, Mona Vale Hospital, AustraliaDisclosure: Nothing to disclose.
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Glucose Tolerance Test Procedure
The GTT procedure is as follows
- At first a zero -time or baseline blood sample is drawn.
- Then the patient is given a specific dose of glucose solution to drink
- After that the blood samples are drawn at regular intervals to measure the blood sugar levels and also insulin levels in certain cases. The blood sampling can be done as requested by the doctor and could involve up to 6 hours of testing.
Influence Of Lower Cutoff Values For 100
Department of Gynecology, Obstetrics and Mastology, Botucatu Medical School, So Paulo State University, So Paulo, Brazil. To evaluate data from patients with normal oral glucose tolerance test results and a normal or impaired glycemic profile to determine whether lower cutoff values for the OGTT and GP could identify pregnant women at risk for excessive fetal growth. We classified 701 pregnant women with positive screening for gestational diabetes mellitus into 2 categories — normal 100-g OGTT and normal GP and normal 100-g OGTT and impaired GP-to evaluate the influence of lower cutoff points in a 100-g OGTT and GP for identification of pregnant women at excessive fetal growth risk. The OGTT is considered impaired if 2 or more values are above the normal range, and the GP is impaired if the fasting glucose level or at least 1 postprandial glucose value is above the normal range. To establish the criteria for the OGTT , we considered the mean , mean plus 1 SD , and mean plus 2 SD and for the GP, we considered the mean and mean plus 1 SD . Subsequently, the women were reclassified according to the new cutoff points for both tests . Consideration of values, in isolation or combination, yielded 6 new diagnostic criteria. Excessive fetal growth was the response variable for analysis of the new cutoff points. Odds ratios and their respective cContinue reading > >
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What Is The Glucose Tolerance Test
Prior to the taking the glucose tolerance test, your doctor will ask you to make sure and eat at least 150 mg of carbohydrates for three days prior to the time you will be asked to fast. You will not be permitted to eat or drink anything but sips of water for 14 hours prior to the test, so it is best to schedule the test for first thing in the morning.
Additionally, you should plan to have someone drive you to and from the test since your energy levels may be low and there is a slight possibility you may feel light-headed.
3-Hour Glucose Test
When you arrive, the technician will draw blood to measure your baseline fasting blood glucose level. You will be asked to drink a larger volume of the glucose drink than was used in the initial Glucose Challenge Screening test. Your blood will be drawn and tested every hour for the next three hours.
The following are the values that the American Diabetes Association considers to be abnormal during the Glucose Tolerance Test:
| Interval |
What Is A Glucose Test During Pregnancy
Glucose tests are used to screen for and diagnose gestational diabetes. They measure how efficiently your body processes sugar, which is key, since pregnancy hormones can affect this natural regulation process. Gestational diabetes is one of the most common pregnancy conditions up to 10 percent of pregnant women in the US develop it, according to the Centers for Disease Control and Prevention . Left untreated, gestational diabetes has some potentially dangerous consequences. An increased chance of preeclampsia, preterm labor and c-section are among the risks Mom may face. Whats more, baby may be born at a higher birth weight or with complications, such as respiratory distress or low blood sugar. Fortunately, proactive monitoring and treatment can help ensure you and baby stay healthy and safe. Suffice to say, the glucose test is a small price to pay.
So exactly what is a glucose testand what does it entail? First, its important to clarify that there are actually two different glucose tests during pregnancy: The first is a screening that identifies if youre at an elevated risk for gestational diabetes. If the initial glucose blood test shows that youre not processing sugar quickly, youll move on to the second, more involved glucose tolerance test. The latter is diagnostic, meaning youll have a definite answer.
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Are There Any Side Effects Associated With The Glucose Tests
Most pregnant women donât have any side effects during or after either glucose test. Its possible that you may feel nauseous, lightheaded, or even sweaty after drinking the glucose solution. It tastes like a very sweet soda, which can be easier to stomach for some women than for others.Youâll need to have your blood drawn, so you might feel dizzy, and you may have slight bruising around the blood withdrawal spot, but otherwise the risks associated with these tests are minimal.
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How Effective Are Oral Glucose Tolerance Tests
An OGTT can be used to effectively diagnose various types of diabetes, including prediabetes.
Its useful for confirming a diagnosis after an abnormal HbA1c test result. An A1C test is often part of routine blood tests, but its less sensitive than an OGTT. Because of this, an OGTT can help with making an official diagnosis.
- recent surgery
This can alter the results, potentially leading to a misdiagnosis.
An OGTT is also time consuming. You may need to take off from work or school. Theres currently no alternative for the test, according to 2018 research.
An OGTT is considered to be a safe test.
Be sure to eat a meal the night before. This may help reduce discomfort caused by fasting.
For some people, drinking the concentrated glucose solution causes side effects such as:
Additional side effects, such as diarrhea and heart palpitations, are more likely to affect people whove had bariatric surgery.
Other OGTT risks are the same as getting your blood drawn for any reason:
- skin irritation from adhesive on a bandage
If you have any concerns, talk with a doctor before taking the test.
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Oral Glucose Tolerance Test
The oral glucose tolerance test, also called the glucose challenge test, is the first glucose screening test carried out during pregnancy.
When the test is carried out:During weeks 24 to 28 of pregnancy, however, it may be done earlier if you are considered high risk.
How it’s carried out:This test does not require you to fast. You’ll be asked to drink a very sweet beverage that contains 50 grams of glucose within five minutes. After one hour, a blood sample is taken to measure the amount of glucose in your blood.
What the test results mean:If blood sugar levels are above 140 milligrams per deciliter , gestational diabetes is suspected, and you may have to return for a three-hour glucose tolerance test. If your blood sugar is over 200 milligrams per deciliter , you may have type 2 diabetes.
Risks And Side Effects
Most people do not experience any side effects from glucose testing, and serious complications are rare.
As it involves fasting and blood testing, the glucose tolerance test might cause nausea, light-headedness, shortness of breath, and sweating in some people.
The doctor uses a needle to draw the blood, so the injection may cause moderate pain for some.
More serious but less common risks include:
- excessive bleeding
The glucose tolerance test is not the only way to diagnose diabetes. Doctors use other tests to diagnose and monitor the condition.
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Glucose Challenge Test Results
What many medical experts consider a normal result for a glucose challenge test is a blood sugar level equal to or less than 140 mg/dL . The mg/dL means milligrams per deciliter and the mmol/L means millimoles per liter. This is how the glucose is measured in your blood sample. A normal result means you do not have gestational diabetes.If your level is higher than 140 mg/dL , your healthcare provider may recommend you do the glucose tolerance test, which can help better determine if you have gestational diabetes or not.
What Abnormal Results Mean
Abnormal blood values for a 3-hour 100-gram oral glucose tolerance test are:
- Fasting: greater than 95 mg/dL
- 1 hour: greater than 180 mg/dL
- 2 hour: greater than 155 mg/dL
- 3 hour: greater than 140 mg/dL
ONE-STEP TESTING
Abnormal blood values for a 2-hour 75-gram oral glucose tolerance test are:
- Fasting: greater than 92 mg/dL
- 1 hour: greater than 180 mg/dL
- 2 hour: greater than 153 mg/dL
If only one of your blood glucose results in the oral glucose tolerance test is higher than normal, your provider may simply suggest you change some of the foods you eat. Then, your provider may test you again after you have changed your diet.
If more than one of your blood glucose results is higher than normal, you have gestational diabetes.
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How To Lower Your Blood Glucose Levels
Even if you have a normal glucose screening and never test positive for glucose in your urine, its still important to follow a healthy diet during pregnancy, which can help stabilize your blood sugar levels.
Here are some tips on what to eat to keep blood sugar spikes at bay, plus other smart strategies:
What About Glucose Tolerance Testing During Pregnancy
As mentioned previously, the glucose tolerance test is used for the diagnosis of gestational diabetes . It may be used if there are equivocal fasting or random blood glucose results, or to screen for gestational diabetes in pregnant women between 24 to 28 weeks of gestation who are not known to have diabetes.
The test may also be used in the postpartum period to detect diabetes in women who had gestational diabetes during pregnancy. Women who had gestational diabetes do not always develop diabetes later in life, but they should undergo diabetes screening at least every three years throughout their life.
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Diabetes Questions To Ask Your Doctor
What Is The Glucose Challenge Screening Test
No preparation is required prior to the test. During the test, the mother is asked to drink a sweet liquid and then will have blood drawn one hour from having the drink, as blood glucose levels normally peak within one hour. No fasting is required prior to this test.
The test evaluates how your body processes sugar. A high level in your blood may indicate your body is not processing sugar effectively . If the results of this screen are positive, the woman may have the Glucose Tolerance Test performed. It is important to note that not all women who test positive for the Glucose Challenge Screening test are found to have diabetes upon further diagnosis.
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What If I Have Gestational Diabetes
GD is increasingly common, with about 7% of women having the condition. If you are found to have GD, you will work closely with your health care provider to keep your blood glucose levels in a healthy range. This involves choosing a healthy diet, gaining the recommended weight during your pregnancy, getting exercise, and if needed, taking insulin or pills to lower your blood sugar. Your babys wellbeing will be carefully monitored by regular measurements of growth and amniotic fluid volume. If you have GD you will be offered a repeat glucose tolerance test between 6 weeks and 6 months postpartum to detect prediabetes and diabetes. You may also be offered induction between 38-40 weeks of pregnancy. Finally, it is strongly recommended that women with GD breastfeed their infants.
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What Can I Expect If Getting An Oral Glucose Tolerance Test
Before doing an OGTT, a doctor might perform a glucose challenge test first. This is a shortened version of the OGTT.
A glucose challenge test requires no fasting. During the test, youll drink a beverage containing 50 grams of glucose. After 1 hour, a healthcare professional will take a blood sample to check your blood sugar level.
If your blood glucose is higher than 140 mg/dL, it might indicate diabetes. In this case, youll need an OGTT.
An OGTT requires some preparation. Youll need to fast for about 8 hours before the test is performed. This means you cant eat breakfast or drink any liquids, except water, beforehand.
An OGTT includes the following steps:
- A health worker will take a blood sample from your fingertip, earlobe, or a vein. Theyll test the sample for blood glucose, which will serve as a baseline measurement.
- Youll drink a concentrated glucose beverage. Most solutions contain 75 grams of glucose.
- Youll sit or lay down for 1 hour.
- After 1 hour, healthcare staff will take a blood sample.
- A healthcare professional may take another blood sample after 2 hours and again at 3 hours.
- A medical team will measure the blood glucose levels at each test time.
Between testing times, youll need to stay still and avoid drinking a lot of water. Thats because excessive movement and hydration can alter the results.
You might receive an OGTT without receiving a glucose challenge test first.
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What Are The Preparations Needed For Gtt
GTT is an elaborate blood test, that requires frequent testing and as the special requirements need for GTT are as follows
- Have a normal diet like any other day.
- Inform the doctor about the varied prescription drugs you are taking, as certain drugs like corticosteroids, diuretics and anti- depressants can cause false results.
- Fasting is required for 8 to 10 hours prior to the test and only water is allowed during this period.
- You might want to avoid using the washroom prior to testing as urine samples might be needed
- On the morning of the test do not smoke or have coffee or caffeine based product.
- The GTT is not to be done on a sick person
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Who Is At Risk
Risk factors for gestational diabetes include:
- having had gestational diabetes in an earlier pregnancy
- a family history of diabetes
- having obesity or other diabetes-related conditions
- being physically inactive
If a person gains more weight than is usual during pregnancy, this may be a sign of gestational diabetes, according to the
- attending more frequent screening and seeking medical help if glucose levels go up
- insulin use, in some cases
The healthcare provider will advise on each persons needs and treatment plan, as diabetes affects everyone differently.
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