The standard glucose screening test contains 50 grams of sugar, roughly the same amount found in a 20-ounce bottle of soda. If you need the follow-up diagnostic test, that number jumps to either 75 or 100 grams depending on which version your provider uses.
Sugar in the One-Hour Screening
The first glucose test most people encounter, especially during pregnancy, is the one-hour glucose challenge test. You drink a sweet syrup containing 50 grams of pure sugar dissolved in a small amount of liquid. The sugar used is 100% dextrose derived from corn, not high fructose corn syrup. The drink also contains water, citric acid as a preservative, and a small amount of citrus flavoring from natural oils.
Fifty grams of sugar is a lot to consume in a few minutes. For comparison, a regular 12-ounce can of cola has about 39 grams of sugar, and a standard candy bar has around 20 to 30 grams. The difference is that the glucose drink is designed to hit your system fast, giving your body a concentrated sugar load so your blood can be tested at a precise time afterward.
You don’t need to fast before this screening. A blood sample is taken before the drink, then another one hour later to see how your body processes the sugar.
Sugar in the Diagnostic Tests
If your results on the one-hour screening come back high, you’ll be sent for a longer, more detailed test. There are two versions:
- Three-hour test: Uses 100 grams of glucose. This is the traditional follow-up for gestational diabetes screening and requires eight hours of fasting beforehand. Blood is drawn multiple times over three hours.
- Two-hour test: Uses 75 grams of glucose. Some providers use this as a single-step alternative, skipping the 50-gram screening entirely. It also requires an eight-hour fast.
One hundred grams of sugar is roughly equivalent to drinking two and a half cans of soda at once on an empty stomach. That’s why side effects are more common with the longer tests.
What the Drink Tastes Like
The glucose beverage (often sold under the brand name Glucola or Trutol) comes in a few flavors, typically orange, lemon-lime, or fruit punch. Most people describe it as an extremely sweet, flat soda. The flavoring is mild, made from a blend of natural oils rather than artificial additives.
Some people find it tolerable when served cold, while others struggle to finish it. Drinking it quickly is important because the clock for your blood draw starts once you finish. Sipping slowly over 15 or 20 minutes can throw off the results.
Common Side Effects
The concentrated sugar hit can cause nausea, dizziness, or a general feeling of being unwell. These symptoms are especially common with the 75-gram and 100-gram tests taken on an empty stomach. Some people also experience a sugar crash afterward, feeling shaky or lightheaded as their blood sugar drops back down.
Bringing a snack to eat after your final blood draw is a good idea. You can resume eating normally once the test is complete, and having something balanced with protein and fiber can help stabilize how you feel.
Can You Use Alternatives?
You may have heard about using jelly beans or other candy as a substitute for the glucose drink. The idea is appealing, but it doesn’t hold up well in practice. Jelly beans vary in weight and sugar content from brand to brand, and the specific types of sugar they contain aren’t standardized. The Association for Diagnostics and Laboratory Medicine has stated that jelly beans cannot be recommended for the 50-gram screening because of these inconsistencies.
Some companies now sell glucose powders that you mix into 10 ounces of cold water at home, available in 50-gram, 75-gram, and 100-gram versions. These deliver the same standardized dose of dextrose as the traditional drink but give you more control over temperature and how quickly you consume it. Whether your provider accepts these alternatives depends on the lab they use, so it’s worth asking ahead of time.
Why the Sugar Load Matters
The whole point of consuming so much sugar at once is to stress-test your body’s ability to manage blood glucose. When you drink 50 or 75 grams of dextrose, your pancreas responds by releasing insulin to pull that sugar out of your bloodstream and into your cells. In someone with normal glucose tolerance, blood sugar rises and then falls back to a safe range within the testing window. In someone with impaired tolerance or gestational diabetes, blood sugar stays elevated longer than it should.
The specific sugar amounts aren’t arbitrary. They’re calibrated to produce a predictable spike that makes it possible to set clear cutoff values for normal and abnormal results. Using less sugar would make the test less sensitive, potentially missing cases that need treatment. Using more would be unnecessarily uncomfortable without improving accuracy.