The 1-hour glucose screening test, often called the glucose challenge test, is a routine procedure performed during pregnancy to screen for gestational diabetes (GDM). This condition involves elevated blood sugar levels that develop during pregnancy, potentially affecting both maternal and fetal health if left unmanaged. The purpose of the screening is not to be “passed” through dietary manipulation, but to accurately assess your body’s natural response to a glucose load. Correct preparation ensures the test provides a true reading of your body’s ability to process sugar, which is the most reliable outcome for your care.
Essential Preparation in the Days Before
A common but incorrect assumption is that severely restricting carbohydrates before the test will help produce a lower result. Attempting to “diet” or fast can skew the results and potentially lead to a false positive reading. When your body is deprived of its usual carbohydrate intake, the cells become more sensitive to insulin, which can cause an exaggerated or abnormal reaction when suddenly faced with the high glucose load of the test drink. This physiological change may result in a blood sugar reading that is higher than what is typical for your body’s normal daily function.
To ensure the most accurate screening, maintain a consistent, normal, and adequate carbohydrate intake in the two to three days leading up to your appointment. Many health organizations recommend consuming at least 150 grams of carbohydrates per day during this period. This approach ensures that your body is accustomed to processing glucose effectively when the 50-gram glucose solution is administered during the test.
Beyond diet, focus on proper hydration and rest in the days leading up to the test. Dehydration can sometimes concentrate blood glucose levels, potentially leading to a falsely elevated reading on the screening. Adequate sleep is also beneficial, as chronic sleep deprivation can interfere with glucose metabolism and insulin sensitivity.
Specific Instructions for the Morning of the Test
Instructions for the morning of the 1-hour glucose screening vary, but generally, fasting is not required. If your test is scheduled for the morning, consume a balanced breakfast that is low in simple sugars and high in protein and complex carbohydrates. Excellent choices include eggs with whole-grain toast or oatmeal with nuts, which release glucose slowly and steadily.
You must strictly avoid concentrated sugars, such as fruit juices, sugary cereals, pancakes, or pastries, immediately before the test, as these can cause an artificial spike in your blood sugar level. Once you arrive at the clinic or lab, you will be given a bottle containing a 50-gram glucose solution, which you must drink entirely within five minutes. The exact time you finish the beverage must be noted, as the timing of the blood draw is critical to the accuracy of the results.
After finishing the drink, you must not eat or drink anything except small sips of plain water for the next hour. Avoid strenuous activity during this waiting period, as physical exertion can affect your glucose metabolism. Smoking and the use of chewing gum or mints are also prohibited, as they can stimulate digestion or contain hidden sugars. If you are taking any medications, such as steroids, which impact blood sugar levels, discuss this with your physician beforehand, as they may need to adjust your dosage or schedule the test for a different time.
Understanding and Reacting to Your Results
The 1-hour test is a screening, meaning it identifies people who may need further testing, not those who have a definitive diagnosis. Your result will be a blood glucose level measured in milligrams per deciliter (mg/dL) one hour after drinking the solution. Generally, a result below 130 to 140 mg/dL is considered a “pass,” meaning no further testing is required.
If your result is higher than the established cutoff, it indicates that your body’s response to the glucose load was higher than expected. An elevated result on the screening does not automatically mean you have gestational diabetes; it simply means you need to proceed to the definitive diagnostic test. The probability of having GDM increases with the elevation of the 1-hour result, but the diagnosis is not confirmed at this stage.
The next step is the 3-hour oral glucose tolerance test (OGTT). This test requires a full 8-to-14-hour fast beforehand and involves four blood draws: one fasting sample, and three more samples taken at one, two, and three hours after consuming a higher dose of glucose (typically 100 grams). The 3-hour test is considered the gold standard because it provides a comprehensive picture of your body’s ability to clear glucose from the bloodstream. A diagnosis of gestational diabetes is made if two or more of the four blood sugar values on the 3-hour test are above the established thresholds.