3 steps to measuring blood glucose when performing an oral glucose tolerance test

The article was professionally consulted with Doctor Nguyen Thi Man - Obstetrician and Gynecologist - Department of Obstetrics and Gynecology - Vinmec Danang International General Hospital.

Oral glucose tolerance test to diagnose diabetes will measure blood glucose index at 3 times: when fasting overnight, 1h and 2h after drinking sugar solution.

Oral glucose tolerance test is understood as giving the patient a sweet-tasting solution, namely water containing a glucose content of 75g or 100g, then taking blood and testing it. This test is used to diagnose pre-diabetes, clinical diabetes and especially gestational diabetes. Currently, Vietnam is applying diagnostic criteria of the American Diabetes Association (ADA 2016) to read the test results and based on that, to make a conclusion that the pregnant woman has diabetes. or not.
An oral glucose tolerance test is usually ordered for pregnant women who are at high risk for gestational diabetes. Their common characteristics were obesity (BMI ≥ 30), history of diabetes in a previous pregnancy or a family history of diabetes. This test is not intended for subjects with established high blood sugar, classic or acute diabetes symptoms, malnutrition, and bedridden within 3 days.

2.1. First prenatal visit During the first prenatal visit, pregnant women are often assigned to measure blood sugar to screen for diabetes. According to the reference standards of IADPSG (International Association of Diabetes and Pregnancy), if the fasting blood glucose value is in the range of 5.1 - 7.0mmol/L, the pregnant woman is diagnosed with gestational diabetes. In case the blood glucose level is lower than the above parameter, the mother should wait until the 24th to 28th week of pregnancy to continue the oral glucose tolerance test.

2.2. Before the test, pregnant women need to fast for 10-14 hours and do not smoke, use alcohol, exercise heavily or take certain drugs. The total time for the test can take up to 4 hours and the patient is asked to sit still during the process so as not to affect the results.
The blood sugar tolerance test process is conducted in 3 steps as follows:
Step 1: Take the first blood sample when the pregnant woman has just arrived at the clinic. This blood sample must be guaranteed to measure when the body is fasting and is the standard to compare the results of two blood glucose readings later. Step 2: The patient will be given a sugar drink with a common glucose content of 75g. Step 3: Pregnant women sit still and wait for about 1 hour, then a second blood sample will be taken to measure and record the results. The third blood draw was performed 1 hour later (2 hours after taking glucose). During this test, people can drink water, but should limit exercise. After the results are available, the doctor will diagnose diabetes if there is at least 1 abnormal glucose value, the specific reference index is:
Greater than 5.1 mmol/l (ie 92 mg/dL). ) when fasting Greater than 10.0 mmol/l (ie 180 mg/dL) after 1 hour Greater than 8.5 mmol/l (ie 153 mg/dL) after 2 hours. If the blood glucose index after 2 hours is in the range of 140-199 mg/dl, the pregnant woman is likely in a pre-diabetic state.

For example, a pregnant woman with a fasting blood sugar level above the fasting threshold of 97 mg/dl, the doctor can conclude that she has gestational diabetes. However, there is no need to worry too much because this fasting glucose value only increases slightly. Up to 70% of gestational diabetes cases are still healthy and safe thanks to a healthy diet, scientific diet, combined with regular and reasonable physical activity. Some tips that patients need to follow right from the pre-diabetes stage include:
Adjust diet: Avoid foods high in sugar, limit starches and fats. Supplement necessary nutrients such as protein, fiber, vitamins, ... with green vegetables. Split meals: In order to avoid overeating or abstaining from overeating, pregnant women at risk of diabetes need to divide their daily meals into 5-6 small meals. Exercise: You can do light exercise such as walking for 15-30 minutes a day or choose specialized exercises for pregnant women with moderate intensity and regularity Weight management: Pregnant women just need to gain enough weight , do not let the weight get out of control because of unreasonable nutrition. For women who already have gestational diabetes, tight blood sugar control is of the utmost importance. It is recommended to test blood sugar regularly, on an empty stomach and after eating (morning, noon, evening) 1 hour, as well as before going to bed. If not, gestational diabetes will lead to many serious complications for both mother and fetus.
In case the oral glucose tolerance test is positive for gestational diabetes, women should not be too worried but instead should strictly follow the advice of the obstetrician, keep a positive spirit together with a healthy lifestyle to ensure the health of both mother and child. On the contrary, if the doctor diagnoses a normal pregnant woman or has signs of pre-diabetes, it is necessary to periodically monitor blood sugar levels and schedule antenatal care.