Blood Tests

Most chronically infected persons show no outward signs of HBV infection.

Screening is necessary to :

  • Identify individuals who have chronic HBV infection so they can receive appropriate medical management.

  • Identify those who are unprotected so they can be vaccinated.

  • Avoid unnecessary vaccination and help reduce costs.  Vaccination is not beneficial for patients already chronically infected with HBV or already immune (either through prior vaccination or a previous resolved acute infection).

1. Hepatitis B surface antigen (HBsAg)
The HBsAg test is the ONLY way to definitively diagnose chronic HBV infection.  By definition, if you remain HBsAg-positive for more than 6 months, then you have developed chronic (lifelong) infection.  

2. Hepatitis B surface antibody (anti-HBs)
The anti-HBs test will tell you if you are protected against HBV.  Anti-HBs can be produced in response to vaccination or recovery from an acute hepatitis B infection.










                                   * If HBsAg remains positive for 6 months



Chronic HBV infection *

HBsAg (+)
anti-HBs (-)

Immune to HBV

HBsAg (-)
anti-HBs (+)

HBsAg (-)
anti-HBs (-)

Unprotected; need vaccination

HBsAg (+)
anti-HBs (+)

Chronic HBV infection *

HBV screening is a simple blood test for the following markers:

Who should get screened for HBV?

2006 guidelines from the Centers for Disease Control and Prevention (CDC) call for routine HBV screening of all foreign-born persons from high endemic areas (see box below) regardless of their immunization history.  This includes immigrants, refugees, asylum seekers, and internationally adopted children.


  • Although a safe and effective recombinant hepatitis B vaccine has been available since 1986, HBV still kills 700,000-1 million people every year worldwide.

  • About 1in 20 people in the world (370 million individuals) are living with chronic HBV infection.

  • Without appropriate monitoring or treatment, 1 in 4 of those chronically infected will die from liver cancer or liver failure.

  • Every 30-45 seconds, one person dies from this vaccine-preventable disease.

The CDC recommends routine HBV screening for all persons born in high endemic regions (HBsAg prevalence of ≥8%):

  • Africa

  • Asia and Pacific Islands

  • Carribean (Turks and Caicos)

  • Eastern Europe

  • Middle East (Saudi Arabia and Jordan)

  • America (Amazon Basin)

  • Alaska, Northern Canada, and Greenland (indigenous populations)



















Other groups recommended for HBV screening include:

  • Household, sex, and needle-sharing contacts of HBsAg-positive persons

  • Pregnant women

  • HIV-infected persons

  • Hemodialysis patients

Where can I get tested?

​If you are a resident in the Bay Area in California, there are several free or low-cost screening and vaccination programs.





















If you know of any other free or low-cost screening and vaccination sites throughout the country, please contact us, and we will add the information this website!

Pacific Free Clinic in Silicon Valley

1835 Cunningham Ave., San Jose, CA 95122

Saturdays from 10 AM – 2 PM


Overfelt High School


Screenings and vaccinations are free


Only for people with no health insurance

San Francisco Hep B Free

San Francisco Hep B Free is a citywide campaign to turn San Francisco into the first hepatitis B free city in the nation


Free and low-cost hepatitis B testing and vaccinations


For all locations:

The Hep B Project:

Wednesdays from 1:30 – 4 PM at 2501 International Blvd, Oakland, CA inside Street Level Health Project


Saturdays from 10 – 11:20 AM at 818 Webster Str, Oakland, CA inside Asian Health Services


Screenings and vaccinations are free


Only for people with no health insurance

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Contact Us

Asian Liver Center

at Stanford University

780 Welch Road, CJ 130
Palo Alto, CA 94304

Stephanie Chao, M.D.
Voice: (650) 736-8608
Fax: (650) 736-8001