6/2024
If you are pregnant or are trying to conceive, one important test to be prepared for is the glucose tolerance test (GTT or glucola). This test screens for gestational diabetes mellitus (GDM), a condition in which carbohydrate intolerance develops during pregnancy. One of the most important things to know is that pregnant persons without any risk factors can still get GDM simply because they have a placenta!
How is GDM diagnosed?
In the U.S. the current standard of care is for all pregnant persons to be screened for GDM with a laboratory-based screening test(s) at 24–28 weeks of pregnancy. The two-step approach to testing for GDM is based on first screening with a 50 gram oral glucose solution (glucose tolerance test-GTT or glucola) followed by a 1-hour venous glucose determination via blood draw. Patients whose glucose levels meet or exceed an institution’s screening threshold (130, 135, or 140) then undergo a 100 gram, 3-hour diagnostic GTT. For the 3 hour GTT, you will fast for 8 hours prior. Once in the clinic/office, your blood will be drawn fasting, then one, two and three hours after drinking the glucola drink. ACOG suggests use of Carpenter and Coustan vs national Diabetes Data Group (NDDG) criteria for the diagnosis of GDM due to higher thresholds with NDDG and possibility of missing patients who would benefit from GDM diagnosis:
- Fasting blood sugar: <95 mg/dL (5.3 mmol/L)
- 1 hour blood sugar: <180 mg/dL (10.0 mmol/L)
- 2 hour blood sugar: <155 mg/dL (8.6 mmol/L)
- 3 hour blood sugar: <140 mg/dL (7.8 mmol/L)
If you have pregestational (before pregnancy) Type 2 diabetes or Type 1 diabetes YOU DO NOT NEED TO TAKE THE GLUCOLA! There is no such thing as having gestational diabetes on top of pregestational diabetes! If you are diagnosed with GDM, it can be managed and you can have a healthy pregnancy and baby. The key is to diagnose it in a timely manner so that you can receive the proper care for your and your fetus’s safety. Watch this video to learn more about what to expect after a diagnosis of GDM:
Why might you receive the glucola early in pregnancy?
Early pregnancy screening for undiagnosed type 2 diabetes (pregestational diabetes), at the initiation of prenatal care or < 20 weeks of pregnancy, is suggested in patients with risk factors, for pregestational diabetes. According to ACOG, early testing should be considered in those who are overweight or obese (ie a body mass index greater than 25 or greater than 23 in Asian Americans) and have one or more of the following additional risk factors:
- Physical inactivity
- First-degree relative with diabetes
- High-risk race or ethnicity (eg, African American, Latino, Native American, Asian American, Pacific Islander)
- Have previously given birth to an infant weighing 4,000g (approximately 9 lb) or more
- Previous gestational diabetes mellitus
- Hypertension (140/90 mm Hg or on therapy for hypertension)
- High-density lipoprotein cholesterol level less than 35 mg/dL (0.90 mmol/L), a triglyceride level greater than 250 mg/dL (2.82 mmol/L)
- Women with polycystic ovarian syndrome
- A1C greater than or equal to 5.7%, impaired glucose tolerance, or impaired fasting glucose on previous testing
- Other clinical conditions associated with insulin resistance (eg, prepregnancy body mass index greater than 40 kg/m2, acanthosis nigricans)
- History of cardiovascular disease
Watch this video to learn more about early screening for diabetes in pregnancy!
Why is the glucola the best option for screening for and diagnosing GDM?
The only validated way to screen for and diagnose GDM is with the glucola beverage. This is endorsed by ACOG and the ADA, along with numerous other major medical organizations. None of the proposed "alternatives" to the glucola have been validated or perform poorly (low sensitivity and specificity) and have not endorsed by ADA or ACOG. In 2017, a Cochrane Library metastudy evaluated and compared different ways of diagnosing GDM. The authors looked at different diagnostic tests including different oral glucose tolerance test loads, a glucose drink, a candy bar and foods high in glucose. There were a number of weaknesses among the studies, including unclear methodology and important gaps in the data. In addition, the quality of evidence as very low. The studies in this review do not provide enough evidence to guide clinical practice and health policy regarding identifying patients with GDM. Other options to the glucola should be reserved for those patients who cannot tolerate it (see below).
What are potential complications of GDM?
For pregnant persons who have GDM, pregnancy complications include preeclampsia, urinary tract infection, hydramnios, increased operative intervention and future diabetes mellitus. For the fetus, GDM is associated with macrosomia, congenital anomalies, metabolic abnormalities, and stillbirth.
What is in the glucola beverage?
In recent years, non-medical social media influencers, bloggers, and other social media accounts have used various tactics to make people believe that the glucola is toxic and dangerous. This tactic is used to deepen the divide in the provider-patient relationship and instill fear and doubt in pregnant persons. It often benefits the person sharing the false information at the potential cost of the patient’s health. Avoid influencers, bloggers, and social media accounts who use these fear-based tactics. The fact is that the glucola drink IS SAFE in pregnancy, but undiagnosed GDM is not.
The glucola beverage is available in 50, 75 & 100 gram concentrations. Flavors include orange, lemon-lime, fruit punch, and unflavored. The lemon-lime flavor and unflavored drinks contain no food dyes. Orange has Natural Orange Flavor # 30 (FD&C Yellow #6 and FD&C Red #40), Fruit punch flavor contains FD&C Red #40. The glucola is non-carbonated and includes water, glucose additive of 100% dextrose [dextrose is derived from corn; however, it is not High Fructose Corn Syrup (HFCS], citric acid (preservative), citrus, sodium benzoate, artificial flavoring. It is dairy-free and free of wheat, barley, rye and oat glutens. It is caffeine-free and certified Kosher.
You can read more about the ingredients here.
Common "concerns" about the glucola on social media
BVO: One concern is that some glucola drinks contain brominated vegetable oil (BVO). BVO is an emulsification agent used in citrus drinks, and can be found in the orange-flavored glucola. It is also a food stabilizer used in soda drinks to help keep citrus-flavor oils suspended and prevent them from floating to the top of the liquid. BVO is allowed as a food additive in Latin American and North American countries (including the U.S. and Canada), but not in Japan or European Union countries. BVO is in many common foods like cake mixes, sports drinks, Jell-O, sauces, boxed macaroni and cheese, candy, chewing gum, butter, cereals, snack foods, cosmetics, beer and more. Concerns about the effects of BVO are related to long-term use, not the amount found in a single glucola drink. According to the FDA, BVO is a safe additive and does not exceed the recommended maximum dose of 15 ppm (parts per million). By this standard, you would have to consume several liters of beverages with BVO to have any negative effect.
BVO is NOT A FLAME RETARDANT, they are totally different products. Apart from the fact that both contain bromine there is no direct connection between BVO and brominated flame retardants. BVO is also in cake mixes, sports drinks, Jell-O, sauces, boxed macaroni and cheese, candy, chewing gum, butter, cereals, snack foods, cosmetics, beer and many more. BVO could be used — and has been patented as — a flame retardant. But the fact that it's patented doesn't mean it's in common use, or related to the vast majority of other brominated flame retardants. The common brominated flame retardants in use are different from the food additive. In addition, the common brominated flame retardants in use have different chemical makeups than BVO. Equating the two would be like comparing Splenda, a sweetener, with bleach, since both contain the element chlorine.
The truth is that most glucola drinks do not contain BVO. In addition, BVO in a glucola drink should not be a reason to avoid the screening and/or diagnostic test for GDM. There are multiple types of the glucola drink. If you are still concerned about BVO or any other ingredient such as color dyes, talk to your obstetrical care provider. They will help you pick one that works for you.
D&C yellow #6 & FD&C Red #40: Certified color additives have special names consisting of a prefix, such as FD&C, D&C, or Ext. D&C; a color; and a number. An example is FD&C Yellow No. 6 (Sunset Yellow), often found in breakfast cereals, sausages, baked goods, chips, orange soda, other beverages, hot chocolate mix, ready to use frostings, dessert powders, candy, gelatin desserts, other foods, cosmetics, medicines. Sometimes a color additive is identified by a shortened form of its name, consisting of just the color and number, such as Yellow 6. Red No. 40 (Allura Red): A dark red dye that is used in beverages, breakfast cereals, baked goods, flavored yogurts, chips, gelatin, dessert powders, candy, other foods, cosmetics, medicines. The most popular food dyes are Red 40, Yellow 5 and Yellow 6. These three make up 90% of all the food dye used in the US. Studies that have evaluated the safety of food dyes are long-term animal studies.Studies using Blue 1, Red 40, Yellow 5 and Yellow 6 found no evidence of cancer-causing effects.
What are the side effects of the GTT?
Some patients may experience nausea and/or vomiting after drinking the GTT. Serving the hyperosmolar glucola drink on ice may reduce nausea and vomiting and make it easier to tolerate. If you vomited during the GTT and are willing to come back another day for repeat testing, premedication with an antiemetic drug, like phenergan or zofran, may be helpful.
What if I cannot tolerate the GTT?
Home blood sugar monitoring
There are no validated alternatives to the glucola for screening for or diagnosing GDM. For those patients who cannot tolerate the glucola (ie bariatric surgery or hyperemesis gravidarum) or who decline to take it, home blood sugar monitoring (accuchecks) may be the best option in those who are considered high-risk for GDM. In this case, doing accuchecks 4 times a day between 24-28 weeks of pregnancy and again at 32 weeks is best. However, this approach will only pick up cases of GDM that need treatment with insulin as it is not a validated screening test. With this method, it is important that patients follow their normal diet while testing, to get a “real-life” picture of their blood sugar results over time. The best alternative for diagnosing GDM in low-risk patients who cannot tolerate the GTT is unknown.
Why "alternatives" to the glucola presented on social media are NOT alternatives
Hemoglobin A1c
A1c measurement is not appropriate for screening or diagnosis of gestational diabetes (GDM). Pregnancy is characterized by abnormal erythrocyte turnover, which increases the likelihood of inaccurate A1c results. In addition, A1c underestimates the degree of glucose intolerance in the late 2nd trimester, the usual time of screening for GDM. As a result, A1c could provide false reassurance if it's used to measure glycemia in mid- to late-gestation without accounting for gestational age and maternal hemoglobin level. In a USPSTF systematic review, no threshold for glycated hemoglobin (A1c) in the 2nd and 3rd trimesters had both good sensitivity and specificity as a screening test for GDM at any threshold (18 studies). Watch this video to learn more!
Candy, a predefined meal, or commercial soft drinks--confectionary options
The oral glucose loads with these options are better tolerated but are less sensitive and have not been validated in large studies. In addition, there are different kinds of sugars in food-, candy-, or drink-based tests and they don’t all have the same effect on blood sugar levels. The glucola beverage was designed specifically with glucose (also called dextrose) and has been validated as a screening and diagnostic test for GDM. In addition, screening for GDM with confectionary options that have different kinds of sugar, fats and proteins and a wide variation in carbohydrate and starch amount do not allow for a clear diagnosis of GDM. This includes the infamous jelly bean test!
Check out this video I recently made on this topic!
Fresh Test
This company has an FDA registered product that contains 50 and 100 grams of glucose as dextrose for the screening and diagnostic tests for GDM. It is ot considered an alternative to the glucola, but rather another brand of sorts that is equivalent to the glucola. Ingredients include non-GMO Dextrose (D-Glucose), crystalized Lemon (Citric Acid, Lemon Oil, Lemon Juice), and Organic Peppermint Leaf Powder. It is dye free, and contains no artificial flavoring, GMOs, sodium benzoates, BVO, BPA, and other preservatives. It can be bought on their website and some clinics/offices have available for purchase or included in their pregnancy care package. It may be covered by insurance companies, but is largely an out of pocket expense. There are no studies of The Fresh Test in pregnancy. There are no studies comparing it to the standard glucola for side effect profile, nor any studies on the sensitivity and specificity for screening for or diagnosing GDM. It is assumed that because it has the same amount of glucose, it will perform equally to the glucola for screening for and diagnosing GDM. My opinion is that if you have no risk factors for GDM, this can be considered in place of the glucola.
Watch this video!
Let's wrap it up!
To summarize, the GTT with the glucola drink is an important test and can be life-saving for those who are found to have GDM. If you have questions or concerns about the specific drink you’ll be administered during the test, speak with your healthcare provider. Your healthcare provider can work with you to ensure that you are safe, comfortable, and fully educated on the test and process.
Additional resources
- Screening for Gestational Diabetes, USPSTF Recommendation Statement, US Preventive Services Task Force, JAMA, 2021.
- Cochrane Review, Different strategies for diagnosing gestational diabetes to improve maternal and infant health, Farrar et al 2017.
- CLARIFICATION REGARDING ARTICLES STATING THAT BROMINATED VEGETABLE OIL IS A FLAME RETARDANT
- Does Mountain Dew Contain the 'Dangerous Chemical' BVO?
- How Safe are Color Additives?
- Gestational Diabetes Mellitus, ACOG Practice Bulletin, Number 190, February 2018
- Go to my IG highlight on diabetes for more Info!