Hepatitis B Profile Blood Test

Hepatitis B surface antigen (HBsAg) is a protein found on the outer surface of the hepatitis B virus. It's the first marker to appear after infection, typically becoming detectable 4-10 weeks after exposure (average 6 weeks), often before symptoms develop. HBsAg is the hallmark of hepatitis B infection—if present, you are infected with the virus and potentially infectious to others. The pattern of HBsAg over time helps distinguish acute from chronic infection. In acute hepatitis B, HBsAg typically appears, persists for several weeks to months during the symptomatic period, and then clears as the immune system eliminates the virus—most healthy adults (over 95%) clear the virus within 6 months. If HBsAg remains positive for more than 6 months, this indicates chronic hepatitis B infection. Chronic infection occurs more frequently in those infected at birth or in early childhood (up to 90% become chronic carriers) than in those infected as adults (less than 5% become chronic). A positive HBsAg result means you currently have hepatitis B infection and can transmit the virus to others through blood, sexual contact, or from mother to baby during birth. Further testing is needed to determine whether this is acute or chronic infection and to assess liver damage. A negative result means you don't have a current detectable infection, though it doesn't rule out very recent exposure (during the window period) or past infection that has cleared. Results require clinical interpretation and follow-up with your GP.

Hepatitis B surface antibody (HBsAb or anti-HBs) is produced by the immune system in response to the hepatitis B surface antigen. It appears after recovery from acute hepatitis B infection (once HBsAg has cleared) or after successful vaccination. Anti-HBs is a protective, neutralising antibody—its presence indicates immunity to hepatitis B. After natural infection, anti-HBs typically appears weeks to months after HBsAg clears and usually persists for life, providing long-term protection against reinfection. After vaccination, anti-HBs appears 1-2 months after completing the vaccine course. An anti-HBs level of 10 mIU/mL or above is considered protective. Levels above 100 mIU/mL indicate strong immunity. Over time, anti-HBs levels may decline, but immune memory typically persists, and most immunocompetent people remain protected even if antibody levels fall below the detectable threshold. Interpreting your result: A positive anti-HBs with negative HBsAg indicates immunity—either from past infection that has resolved or from vaccination. To distinguish between these, anti-HBc (below) is helpful: positive anti-HBc indicates past natural infection; negative anti-HBc with positive anti-HBs indicates vaccine-induced immunity. A negative anti-HBs with negative HBsAg and negative anti-HBc indicates you're susceptible to hepatitis B and would benefit from vaccination. Results require clinical interpretation and follow-up with your GP.

Hepatitis B core antibody (HBcAb or anti-HBc) is produced in response to the hepatitis B core antigen (HBcAg), a protein found in the inner core of the virus. Unlike HBsAg, HBcAg isn't present in the blood (it remains inside the virus and infected liver cells), but the antibody response to it is readily detectable. Anti-HBc appears early during acute infection, shortly after HBsAg, and typically remains detectable for life. Anti-HBc is the most sensitive marker of hepatitis B exposure—if positive, you have been infected with hepatitis B at some point (naturally acquired infection). Importantly, anti-HBc does NOT appear after vaccination, only after natural infection. This makes it the key marker for distinguishing vaccine-induced immunity (anti-HBs positive, anti-HBc negative) from immunity due to past natural infection (anti-HBs positive, anti-HBc positive). The total anti-HBc test (used in this panel) detects both IgM (recent/acute infection) and IgG (past infection) antibodies together. Interpreting your result: Positive anti-HBc indicates past or current hepatitis B infection—it will be positive in acute infection, chronic infection, and resolved past infection. To determine which, it must be interpreted alongside HBsAg and anti-HBs: (1) HBsAg positive + anti-HBc positive = current infection (acute or chronic); (2) HBsAg negative + anti-HBc positive + anti-HBs positive = past infection, now immune; (3) HBsAg negative + anti-HBc positive + anti-HBs negative = several possibilities including resolving acute infection, remote past infection with waned antibodies, chronic low-level infection, or false positive—further testing may be needed. A negative anti-HBc means you've never been naturally infected with hepatitis B. Results require clinical interpretation and follow-up with your GP.