Anti-HBs is the antibody your body makes against the surface protein of the hepatitis B virus, and its value shows whether you are protected. From 10 IU/l upward, protection is the international reading. Below that threshold the story is more nuanced than most people think.
You usually meet this value after a vaccination, during a work medical, or simply because you want to know where you stand.
Below you will read what anti-HBs is, what the numbers mean and how it relates to the other hepatitis B markers.
What is anti-HBs exactly?
It is the antibody against HBsAg, the surface antigen of the hepatitis B virus. You make anti-HBs after being vaccinated, or after your body has cleared an infection itself. In both cases it signals that your defences can neutralise the virus.
The abbreviation stands for antibody to hepatitis B surface antigen. The lab measures how much of it is in your blood, expressed in international units per litre.
Background on the marker itself is on our anti-HBs page. We cover the broader topic in our piece on the hepatitis B vaccination.
How high should your anti-HBs value be?
The internationally used threshold is 10 IU/l. Above it counts as demonstrated protection. Many labs also report whether you are well above that line, because a higher value generally takes longer to sink below the detection limit.
That 10 is a convention, not a law of nature. Research shows the threshold was chosen on the safe side.
A 2016 study also points out that a value above 10 IU/l gives no absolute guarantee, and that cellular memory matters at least as much. So the number is a good indication, not the whole picture.
What does a value below 10 IU/l mean?
That there are no demonstrable antibodies at this moment. It does not automatically mean you are unprotected, because your immune memory can be perfectly intact while the antibodies have faded.
In a cohort of 1,030 vaccinated students from 2019, even at a value above 2 IU/l most participants responded quickly and strongly to an extra shot. Their immune system had not forgotten the virus.
Still, a low value is a reason to check in, certainly if you work in healthcare or belong to a risk group. The occupational doctor or GP then looks at your whole situation.
Roughly one in ten people make no demonstrable antibodies at all after a full series. Research from 2020 among more than fifteen thousand tested people linked that to older age at vaccination, a higher BMI and smoking.
Anti-HBs, HBsAg and anti-HBc: what is the difference?
These three markers look alike but tell very different stories. Together they show whether you are protected, whether you carry the virus, and where your protection came from.
| Marker | What it measures | What it usually means |
|---|---|---|
| Anti-HBs | Antibody against the surface protein | Protection, from vaccination or a cleared infection |
| HBsAg | The virus surface protein itself | The virus is present, possibly chronic |
| Anti-HBc | Antibody against the core of the virus | You genuinely had the infection at some point |
The useful thing about anti-HBc is that vaccination does not produce it. If you only have anti-HBs, that fits vaccination. If you have anti-HBs and anti-HBc, your body overcame the infection itself.
If HBsAg is detectable, the situation is different and further investigation is needed. What that marker measures is on our HBsAg page.
When do you have anti-HBs measured?
Usually for one of three reasons. You want to know whether a vaccination from years ago took hold, you need it for work or a training course, or you have lost your vaccination record.
There is a fourth, practical reason: peace of mind. People with changing sexual partners like knowing this one STI is covered.
When measuring after a vaccination series, it is usually done one to two months after the last shot. Measure much earlier and the build-up is not finished.
How long your vaccination lasts is in our piece on how long a hepatitis B vaccination is valid. If you want it measured, anti-HBs is part of the hepatitis test. Always discuss an unusual result with your GP.
References
- RIVM. Hepatitis B. 2025. rivm.nl
- Polák P, Husa P, Smejkal P, et al. Is it necessary to revaccinate against hepatitis B virus when the titer of anti-HBs drops below 10 IU/L? Klin Mikrobiol Infekc Lek. 2016. PMID 27907975.
- Significance of anti-HB levels below 10 IU/L after vaccination against hepatitis B in infancy or adolescence. Hum Vaccin Immunother. 2019. PMID 31487228.
- A simple clinical score to identify likely hepatitis B vaccination non-responders. BMC Infect Dis. 2020. PMID 33238923.
Every blood test result at Discreet Test includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
الكاتب
Discreettest
Dr. Naimi، طبيب مسجل في سجل BIG الهولندي، يشرف على المعايير الطبية لمحتوانا وتقييماتنا. اقرأ سياستنا الطبية
