Is fasting required for the hepatitis B surface antigen (HBsAg) and antibody tests?

Sep 03, 2025 Source: Cainiu Health

Dr. Gao Jun

Introduction

In general, fasting is not required for the hepatitis B surface antigen test (HBsAg) and related tests. It is recommended to maintain a normal routine the day before the test, avoid staying up late or drinking alcohol, and reduce the impact of physical abnormalities on the overall health assessment. However, if other tests such as liver function, blood glucose, or lipid profile that require fasting are also being performed, you should fast as required to avoid affecting the results of those tests.

Generally, hepatitis B surface antigen test (HBsAg) does not require fasting. Detailed explanation is as follows:

The hepatitis B surface antigen test primarily detects hepatitis B virus-related antigens and antibodies in the blood, such as hepatitis B surface antigen, e antigen, core antigen, hepatitis B surface antibody, and e antibody. The levels of these substances in the body are stable and not affected by food intake; therefore, fasting is not required. Although indicators such as blood glucose and blood lipids may fluctuate after eating, these fluctuations do not interfere with the detection results of antigens and antibodies. Individuals being tested can go for the test at any time and can eat and drink normally before the test without deliberately fasting, which will not negatively affect the accuracy of the final results.

It is recommended to maintain a normal routine the day before the test, avoid staying up late or drinking alcohol, to reduce interference caused by abnormal physical conditions on the overall health assessment. If other tests such as liver function, blood glucose, or blood lipids that require fasting are also needed, fasting should be done as required to avoid affecting the results of these tests. After receiving the test report, if any indicators are abnormal, timely consultation with a professional is necessary to understand the implications of the results and take appropriate actions. During the test, cooperate with the medical staff to complete the blood collection process to ensure smooth implementation.

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How to determine normal results for the five hepatitis B tests

Under normal circumstances, the main results of the five hepatitis B tests include all negative, only hepatitis B surface antibody positive, and hepatitis B surface antigen negative with hepatitis B surface antibody positive. Additionally, determining whether the five hepatitis B test results are normal requires a comprehensive analysis of all indicators; a single result should not be viewed in isolation. If there are doubts about the test results or if the hepatitis B surface antigen is positive, further evaluation may be necessary.

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What is the difference between "big three positive" and "small three positive" in hepatitis B?

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Can hepatitis B 'small three positives' be transmitted between spouses?

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