References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
The hepatitis B core antibody (anti-HBc) test is a blood test that detects antibodies to the core of the hepatitis B virus. Unlike surface antibody (which shows immunity from either past infection or vaccination), core antibody only appears after actual exposure to the virus. Understanding what core antibody means helps you interpret your hepatitis B testing results.
Here’s what to know.
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What Core Antibody Shows
| Result | Meaning |
|---|---|
| Anti-HBc positive, HBsAg positive | Current hepatitis B infection |
| Anti-HBc positive, HBsAg negative, Anti-HBs positive | Past infection, now immune |
| Anti-HBc positive, HBsAg negative, Anti-HBs negative | Past infection with unclear status — may need follow-up |
| Anti-HBc negative, Anti-HBs positive | Immune from vaccination only |
| All negative | No exposure and no vaccination |
Why Core Antibody Matters
Core antibody is important because:
- It’s only produced after actual infection — vaccination doesn’t cause it
- It distinguishes natural immunity from vaccine immunity
- It identifies occult hepatitis B in some cases
- It matters for blood donation screening
- It helps monitor patients who may be reactivating hepatitis B
IgM vs IgG
- Anti-HBc IgM — present in acute or recent infection
- Anti-HBc IgG — present in past or chronic infection (lifelong marker)
Home Finger-Prick Tests
Some home test kits include core antibody testing using finger-prick blood samples. They can be a convenient way to check hepatitis B status without a clinic visit. Make sure the kit you choose is CE-marked and uses reputable lab processing.
When Core Antibody Testing Is Used
- Investigating possible past hepatitis B
- Confirming immunity from past infection
- Pre-treatment screening (some chemotherapy or immunosuppressive drugs can reactivate hepatitis B)
- Blood donor screening
- Distinguishing natural immunity from vaccine immunity
Isolated Core Antibody
Sometimes people have only core antibody positive — no surface antigen and no surface antibody. This can mean:
- Remote past infection with waning antibodies
- Occult hepatitis B (virus still present at very low levels)
- False positive
- Window period of acute infection
Further testing may be needed including HBV DNA (viral load).
What to Do With Results
- Discuss with your GP or sexual health clinician
- Understand what each marker means
- Follow up if results are unclear
- Get vaccinated if you’re not immune and at risk
Read more: Hepatitis B test kits | Hepatitis B and HIV | Hepatitis B and C
Frequently Asked Questions
Does a positive core antibody mean I’m still infected?
Not necessarily. Core antibody alone shows past exposure — other markers determine current status.
Can the vaccine cause a positive core antibody?
No. Vaccination only causes surface antibody, not core antibody.
Should I get the vaccine if I’m core antibody positive?
Usually not — you already have natural immunity. Your doctor will confirm based on the full picture.
Related reading
- Blood Test for Syphilis, Hepatitis B and Hepatitis C
- Hepatitis B Test Kits: What to Know
- Hepatitis C Testing: A Complete Guide
- Can You Die From Hepatitis B?
- Can You Have Chlamydia and Test Negative?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
