Gestational Diabetes Testing
There are two tests for gestational diabetes.
The 1 hour glucose test and the 3 hour glucose tolerance test (which nobody enjoys taking – plan to spend a lot of time in the waiting room!)
What is this test for? The glucose tolerance test is used to screen pregnant women for gestational diabetes, a temporary form of hyperglycemia, between the gestational weeks 24 and 28. You may be tested earlier due tohealth or family history of diabetes or pregnancy with diabetes.
1 Hour Glucose Test
The most common glucose tolerance test is the 1-hour oral glucose tolerance test (OGTT). To prepare for this test, you must not to eat or drink anything, besides water, after midnight. Most likely your test will be in the morning hours so that you don’t have to go without food for long. Once you arrive to the lab, you will be required to drink a liquid containing a concentrate of glucose. There are usually 2 flavors, but everyone agrees that the orange is the best tasting one. It doesn’t come close to an orange soda and is sickly sweet. This 6 to 8 ounce liquid contains approximately 50 grams of glucose. The best advice is to down the drink as fast as you can.
Most likely you will be asked to do a urine test at the beginning and at the end of your testing, along with with getting your blood is drawn to test your sugar level.
What do the test results inform the doctor? The results from this test will indicate if you are producing enough insulin to handle the 50 grams of glucose. If the reading shows your blood sugar levels are too high, you will be required to come back for a 3 hour test to get a more accurate reading. Why is it more accurate? The lab will draw blood every hour along with taking an urine test each hour to determine what your body is doing over a greater length of time.
Many women can fail the first 1 hour glucose test and take the 3 hour glucose test and pass with flying colors (it’s not uncommon). This will typically happen to women who may have failed the 1st test by a small number. The greater your blood sugar level, the worse your chances for passing the 2nd test. Your doctor will make the determination if they see a reason for your to repeat the test. Depending on how great your number, they may just bypass the 2nd test and go forward with a good gestational diabetes meal plan to bring stability to your blood sugar levels for the rest of the pregnancy. But usually your glucose level will need to be higher than 200 mg/dL for a doctor to declare you as diabetic.
Gestational Diabetes Screening: 1-Hour Glucose Tolerance Readings
| GLUCOSE LEVEL | INDICATION |
|---|---|
| Less than 140* mg/dL (7.8 mmol/L) | Normal screen |
| 140* mg/dL (7.8 mmol/L) and over | Abnormal, needs OGTT (see below) |
| * Some use a cutoff of >130 mg/dL (7.2 mmol/L) because that identifies 90% of women with gestational diabetes, compared to 80% identified using the threshold of >140 mg/dL (7.8 mmol/L) but this can cause many false positives which will require the pregnant mom to take the 3 hour glucose tolerance test. | |
3 Hour Glucose Tolerance Test
So, you didn’t pass and need to sit in a waiting room for 3 hours. Before leaving the house, bring a book/or Kindle, your laptop, your iPad, whatever you need to keep yourself occupied. You will NOT be able to leave. My lab allowed me to walk around the building, but not for long. The lab technicians will want to keep your exercise to a limit to get a true reading of your blood sugar.
This time around, your 50 grams of sweet tasting glucose drink will increase to 100 grams (it’s okay, you can groan – I know it’s not fun, I’ve been there).
Preparation for the test. About 10 to 14 hours before the test, you cannot eat or drink anything except for water. Try to schedule the test for the 1st appointment in the early morning. You won’t be able to eat anything for 3 hours, so plan to miss your breakfast.
The Test. The first sample of blood is drawn to take a baseline reading. Next you will drink a glucose solution that contains 100 grams of sugar. Many women get nauseated drinking the solution, but you need to drink it quickly for the test results to be accurate. If you throw up any of the solution, you will need to come back a different day to take the glucose tolerance test. So, take a deep breath and focus on finishing it quick but keeping it down.
At each hour, you will get your blood drawn and need to give an urine sample. The lab technician should alternate arms when withdrawing blood each time, to give your arms a break. If they don’t, remind them!
You will have a total of 4 glucose blood readings (1 baseline, and 3 follow up). If one of the glucose readings is abnormal, you may need to take another test later in your pregnancy or your doctor may make some changes to you diet and exercise regimen. If 2 or more readings are abnormal, you will need to talk with your doctor about a gestational diabetes treatment plan.
The American Diabetes Association considers these abnormal blood glucose readings:
- Fasting = 95mg/dl or higher
- One Hour = 180mg/dl or higher
- Two Hours = 155 mg/dl or higher
- Three Hours = 140 mg/dl or higher
Passing Results would appear as:
3 Hour Gestational Diabetes Glucose Tolerance Readings
| TIME OF SAMPLE COLLECTION | TARGET LEVEL |
|---|---|
| Fasting* (prior to glucose load) | 95 mg/dL (5.3 mmol/L) |
| 1 hour after glucose load | 180 mg/dL (10.0 mmol/L) |
| 2 hours after glucose load | 155 mg/dL (8.6 mmol/L) |
| 3 hours after glucose load* | 140 mg/dL (7.8 mmol/L |
| INDICATION: If two or more values meet or exceed the target level, gestational diabetes is diagnosed. | |
| * A 75-gram glucose load may be used, although this method is not as well validated as the 100-gram OGTT; the 3-hour sample is not drawn if 75 grams is used. | |
Diagnosed with Gestational Diabetes
If you receive a gestational diabetes diagnosis, your doctor will come up with a diet and exercise plan to manage your condition.
In addition to the above screening tests, more tests may include:
- Glycosylated hemoglobin (HbA1c)— A blood test which reflects the cumulative changes in your blood sugar over the last three months
- Urine tests—protein (24-hour collection) for ketones
- Thyroid function tests: TSH and free thyroxine test
- Tests to check the fetus— Ultrasound (usually done at 30-32 and 36-38 weeks), counting of fetal movement, amniotic fluid analyses
The Importance of Testing
If you have gestational diabetes, your doctor will usually order glucose levels throughout the rest of your pregnancy and continue monitoring you after delivery.
More Information About Gestational Diabetes
Gestational Diabetes During Pregnancy – Gestational Diabetes Blood Sugar
Gestational Diabetes and Baby – Diagnosis of Gestational Diabetes
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