Will Eggs Mess Up a Glucose Test? Get the Facts

January 1, 2026 •

4 min read

Research indicates that eggs have a minimal impact on blood sugar levels due to their low carbohydrate content. However, the key question of 'will eggs mess up a glucose test?' depends entirely on the specific type of test you are taking and the instructions from your healthcare provider.

Quick Summary

Eating eggs before a glucose test is only appropriate for some screenings, not for fasting tests. The effect depends entirely on the type of test, as eggs themselves have little impact on blood sugar.

Key Points

Know Your Test: Preparation depends on whether you're taking a fasting glucose test or a glucose screening, so confirm which one it is.
Eggs are Low-Carb: Eggs themselves are low in carbohydrates and won't significantly spike your blood sugar on their own.
Fast for Fasting Tests: For any test requiring strict fasting (typically 8-12 hours), do not eat eggs or any other food or drink besides water.
Eggs are Okay for Some Screenings: Before some non-fasting glucose screenings (e.g., in pregnancy), a balanced breakfast with protein like eggs is often acceptable and recommended.
Follow Clinic Rules: Always follow the specific, individualized preparation instructions provided by your healthcare provider to ensure accurate results.

The Core Question: Test Type Matters

When asking, "Will eggs mess up a glucose test?" the most critical factor is the specific type of test being performed. There is no one-size-fits-all answer, as the preparation protocol can differ significantly between a routine glucose screening and a strict fasting test. In short, eggs can be part of a balanced meal before a glucose screening, but are forbidden before any test that requires fasting. The difference in requirements is designed to provide an accurate reading for the intended purpose of each test.

Eggs and Their Impact on Blood Sugar

Understanding why eggs are treated differently than other foods is important. A large egg contains less than one gram of carbohydrates, minimal sugar, and no fiber. The body primarily breaks down carbohydrates into glucose, causing a rise in blood sugar. Because eggs are low in carbohydrates and high in protein and fat, they do not cause a significant spike in blood glucose on their own. In fact, the protein and fat content can help slow digestion and stabilize blood sugar when eaten as part of a meal. This makes eggs a much better choice than sugary, refined carbohydrate options like pastries or juices before a non-fasting screening test. However, this minimal impact is irrelevant when strict fasting protocols are required for certain diagnostic tests.

Preparing for Specific Glucose Tests

Fasting Blood Glucose Test

For a fasting blood glucose test (also known as a fasting plasma glucose or FPG test), strict fasting is mandatory. Patients must consume nothing but water for at least 8 to 12 hours before the test. This rule applies to all food and beverages, including eggs, coffee, tea, and gum. The purpose of this test is to measure your blood sugar level on an empty stomach to establish a baseline. Any food, even a small, low-carb meal of eggs, will interfere with the baseline reading, potentially yielding inaccurate results. Informing your healthcare team if you ate by accident is crucial, as the results will be interpreted differently.

Oral Glucose Tolerance Test (OGTT)

The OGTT is a more involved test used to diagnose prediabetes, diabetes, or gestational diabetes. It begins with a fasting blood draw, followed by consuming a high-sugar beverage, and then subsequent blood draws over several hours. For the initial fasting period of 8 to 12 hours, no food or drink (besides water) is allowed. During the test itself, no food is permitted. Therefore, consuming eggs is not allowed for an OGTT.

Glucose Screening (Pregnancy)

Many pregnant individuals receive a one-hour glucose screening test between weeks 24 and 28. This test typically does not require fasting beforehand. For this screening, providers often recommend a balanced breakfast that avoids concentrated sugars and refined carbohydrates. Eggs, paired with whole-grain toast or vegetables, are an excellent choice as a protein-rich option to help keep blood sugar steady and avoid a sugar spike before the test. Following these guidelines can help prevent a false positive and the need for a follow-up three-hour OGTT.

Comparison of Glucose Test Preparations


Feature	Fasting Blood Glucose Test (FPG)	Oral Glucose Tolerance Test (OGTT)	Glucose Screening (Pregnancy)
Purpose	Measures baseline blood sugar on an empty stomach.	Diagnoses prediabetes, diabetes, or gestational diabetes.	Screens for gestational diabetes during pregnancy.
Fasting Required	Yes, 8-12 hours prior.	Yes, 8-12 hours prior to the first blood draw.	Generally no, but strict sugar avoidance is advised.
Can I Eat Eggs?	No. Any food invalidates the fasting result.	No. Fasting is required before the test begins.	Yes, as part of a balanced, low-sugar breakfast.
Other Food Rules	Only water allowed.	Only water allowed during fasting; no food during test.	Avoid sugary foods, refined carbs, and juice on the day of the test.

The Critical Importance of Following Your Doctor's Instructions

While general guidelines exist, it is essential to always follow the specific instructions provided by your healthcare provider. Your doctor's instructions are the definitive source of information and may vary based on your individual health needs, medical history, and the specific test being ordered. Do not attempt to "hack" the test by changing your diet dramatically in the days leading up to it, as this can also produce inaccurate results. If you are unclear about the rules for your test, contact your provider's office for clarification. They can confirm whether fasting is necessary and if a light meal, like eggs, is permissible.

Conclusion: The Verdict on Eggs and Glucose Testing

So, will eggs mess up a glucose test? For tests requiring fasting, such as the standard fasting blood glucose test and the oral glucose tolerance test, eating eggs will absolutely interfere with the results. For these diagnostic tools, fasting is non-negotiable. However, for a one-hour glucose screening during pregnancy, a balanced breakfast including eggs is often a safe and recommended choice, as the protein can help stabilize your blood sugar. Always confirm the specific preparation instructions for your particular test with your healthcare provider to ensure the most accurate and reliable results.

Mayo Clinic Press on fasting guidelines

Frequently Asked Questions

Yes, you can eat eggs or any other normal food the night before a fasting glucose test, as long as your meal is finished before the fasting period begins (typically 8-12 hours before your test).

A glucose screening aims to see how your body handles a sugar load after a typical, balanced meal. A fasting test, however, requires a baseline glucose level with no food interfering. The different test purposes dictate different prep rules.

If you accidentally eat eggs before a fasting test, you must inform your healthcare provider. Eating invalidates the test results, and it will need to be rescheduled for accuracy.

A large egg contains less than one gram of carbohydrates, so the egg itself has a minimal impact on blood sugar. The issue arises from needing to fast completely for certain tests, not from the eggs' carb content.

For a non-fasting glucose screening, a balanced meal high in protein and low in sugar is recommended. Examples include scrambled eggs with vegetables, or plain Greek yogurt with nuts.

No, drinking water during the fasting period is generally acceptable and often encouraged to stay hydrated. However, no other beverages, including coffee or tea, are permitted.

No, skipping meals or drastically changing your diet before a test is not recommended. This can lead to inaccurate or unreliable results and does not truly reflect your body's glucose processing.