The glycemic curve is a blood test combined with an oral test that measures glucose tolerance, commonly used to investigate possible diabetes1. The test assesses the body’s ability to process blood glucose and is frequently ordered during pregnancy.
How the Test Is Done
The test must be done after fasting for 8 to 12 hours and in the morning. In addition, no physical exercise should be performed before the test, as it may cause changes in blood results.
Some medications are prohibited the day before and on the day of the test, such as laxatives. The procedure starts with drawing blood while fasting. Then, the nurse brings a cup of a sugary liquid, very similar to glucose syrup, which should be drunk immediately. The liquid tastes like very sweet lemonade and is usually served cold to make it easier to drink.
After some time, another blood sample is taken. The intervals may vary and are determined by the doctor. The test should be carried out with the patient lying down or sitting comfortably, due to the long fasting period which can cause dizziness, and because the ingested liquid may cause nausea. In pregnant women, extra care is needed because there may be a reaction due to possible gestational diabetes.
Reference Values
The reference values for a glycemic curve test considered normal are:
- Fasting: blood glucose should be below 92 mg/dL
- Sample taken 2 hours after glucose intake: up to 153 mg/dL
For altered results above 125 and 200 mg/dL, gestational diabetes is already considered.
Glycemic Curve Test in Pregnant Women
The glycemic curve test2 is one of the most important during prenatal care. It is ordered to check for possible type 2 diabetes or gestational diabetes, which can pose major risks for the mother and baby.
The procedure for pregnant women is the same and fasting is required for the blood draw. After the glucose dose is taken, a new blood sample is collected for glucose level assessment.
In some cases, the test may last up to 4 hours and require 2 to 3 samples for analysis.
It should also be performed with the pregnant woman lying down comfortably to prevent falls and feeling unwell. No food is allowed during the test, not even water.
When to Take the Test
Usually, the test is ordered between the 24th and 28th week of pregnancy (6 months) and, if necessary, it may be repeated later in the pregnancy. Monitoring glucose and checking for possible gestational diabetes is essential for a healthy pregnancy because high blood glucose during this time can seriously jeopardize the baby’s health.
For example, it increases the chances of preterm birth, early water breaking, and makes the baby grow larger than expected. The risks of complications during birth also rise, as well as the chances of the baby experiencing hypoglycemia3.
The reference values for the gestational glycemic curve test are:
- Considered normal – below 140 mg/dL
- Decreased glucose tolerance – between 140 and 199 mg/dL
- Considered diabetes – above 200 mg/dL
When values are higher than expected, it is common for the test to be repeated after a few days for another analysis and confirmation. Proper follow-up will be necessary and additional tests may be requested.
See also: Glycemia in Pregnancy – How to Take Care?
