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Blood Test Tracker

Hepatitis B Virus DNA (Quantitative)

Measures how much hepatitis B virus DNA is in your blood. It helps show how active a long-term hepatitis B infection is.

AI-verified against cited sources. Awaiting expert reviewAlso called HBV DNA, HBV VLLOINC 42595-9

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What it is

Hepatitis B is a virus that infects the liver. This test uses a very sensitive method called PCR to count the virus's genetic material (DNA) in your blood. Most labs report the answer in international units per milliliter (IU/mL), and many also print a log number. The test is mainly used for people who already know they have hepatitis B. It is not the usual first test to find out whether you have been infected.

Why it matters

For people with long-term (chronic) hepatitis B, the amount of virus helps clinicians judge how active the infection is. It also helps them decide whether treatment may be needed and whether treatment is working. It is read together with liver enzymes such as ALT, e-antigen (HBeAg) status, and sometimes imaging or a fibrosis check. The number alone does not show how much liver damage there is. The test is also used to watch for the virus becoming active again in people with past or inactive hepatitis B who take medicines that weaken the immune system.

If it’s high

Detectable HBV DNA means the virus is multiplying in your body, and a higher number means more virus in your blood. How much this matters depends on your e-antigen (HBeAg) status, your ALT and the health of your liver. In its 2018 guidance, AASLD uses 2,000 IU/mL and 20,000 IU/mL as key levels when deciding about treatment. Your clinician will look at the whole picture.

Common causes

  • Long-term (chronic) hepatitis B that is not being treated
  • The early 'immune-tolerant' phase, when the virus level is very high (often above 1 million IU/mL) and liver tests are often normal or only slightly raised
  • A flare of liver inflammation (the 'immune-active' phase)
  • A recent (acute) hepatitis B infection
  • Missed doses of antiviral medicine or a gap in treatment
  • The virus becoming active again during chemotherapy or other treatment that weakens the immune system
  • Less often, a virus that has become resistant to a medicine

What can help

  • Ask your clinician how often your HBV DNA and ALT should be checked in your situation
  • Ask whether you need treatment, an ultrasound or a liver fibrosis check
  • Tell your clinician about any missed doses, and talk with them before any change to a hepatitis B medicine
  • Ask whether household members and sexual partners should be tested or vaccinated

What can affect your result

  • Where you are in the course of infection (the phase) and your HBeAg status
  • Whether you are on antiviral treatment
  • HBV DNA levels go up and down over time, so one result is a snapshot
  • The test brand: most measure from about 5 to 10 IU/mL up to about 10 million IU/mL, so results outside that range may be shown as limits
  • Medicines that weaken the immune system can let the virus become active again
  • How the sample was handled before it reached the lab
  • Sample handling matters: Mayo Clinic Laboratories asks for the serum to be separated within 2 hours of the draw and shipped frozen.
  • Different test brands measure differently. AASLD (2018) says most assays reach from about 5 to 10 IU/mL up to about 7 log10 IU/mL, so very low or very high results may be reported as limits. Use the same lab and test over time when you can.
  • HBV DNA levels naturally go up and down, so one result is a snapshot.

The result reflects the amount of virus at the time of the draw. How fast it changes depends on the phase of infection and whether treatment has started.

When to talk to a clinician

Talk with your clinician soon if your HBV DNA rises after being low or not detected. AASLD (2018) describes the virus becoming active again as a 100-fold (2 log) rise from your baseline, or a level of 1,000 IU/mL or higher after being undetectable. Get medical care promptly for yellow skin or eyes, dark urine, severe tiredness, a swollen belly, or pain in the upper right belly. Go to emergency care for confusion, vomiting blood or black stools.

Questions you could ask

  • Was my last result measured with the same test as this one?
  • What do my HBV DNA, ALT and e-antigen results say together about where I am in the infection?
  • How often should we repeat the HBV DNA test?
  • Do I need an ultrasound or a liver fibrosis check?
  • Should my household members and partners be tested or vaccinated?
  • If my HBV DNA is low or not detected, how often do I still need blood tests?

Questions people ask

What does 'not detected' mean?

No hepatitis B DNA was found above the lowest level the test can measure. For someone on antiviral treatment, this usually means the virus is being kept in check. It does not mean the infection is gone, because other tests such as HBsAg show that. For someone who has never had hepatitis B, no DNA is expected.

What is the log number next to my result?

It is the same result written as a power of 10. Each step up of 1 means ten times more virus. For example, 3 log is 1,000 IU/mL and 4 log is 10,000 IU/mL.

Can I compare results from different labs?

It is best to use the same lab and test over time. Tests differ in how low and how high they can measure, so numbers can differ a little between labs.

Show the science and sources

For clinicians and researchers

Quantitative HBV DNA is measured by real-time PCR on serum or plasma and reported in IU/mL. AASLD (2018) notes that most assays have a sensitivity of 5 to 10 IU/mL and a dynamic range up to 7 log10 IU/mL. Mayo Clinic Laboratories lists 'Undetected' as its reference value and uses the test for HBsAg-positive patients, to follow disease and response to antiviral therapy. AASLD (2018) phase thresholds: immune-tolerant, typically above 1 million IU/mL; immune-active, above 20,000 IU/mL if HBeAg-positive or above 2,000 IU/mL if HBeAg-negative; inactive, below 2,000 IU/mL. For HBeAg-positive adults with compensated liver disease, treatment is considered when HBV DNA is above 20,000 IU/mL after 3 to 6 months of elevated ALT; for HBeAg-negative adults, above 2,000 IU/mL with elevated ALT. Reactivation in HBsAg-positive patients is defined as a 2-log rise over baseline, a level of 1,000 IU/mL or higher after previously undetectable DNA, or 10,000 IU/mL or higher when no baseline exists. Some labs also print copies/mL, but the conversion to IU depends on the assay, so this catalog does not convert it. The 2024 WHO guidelines widen treatment eligibility and support point-of-care HBV DNA testing and reflex testing. Other guidelines (for example EASL) may use different phase names and cut-offs.

LOINC 42595-9 (primary), 48398-2, 29615-2, 45161-7. Specimen: serum-or-plasma.

Sources

  1. Hepatitis B Virus (HBV) DNA Detection and Quantification by Real-Time PCR, Serum (test HBVQN), Mayo Clinic Laboratories
  2. Update on prevention, diagnosis, and treatment of chronic hepatitis B: AASLD 2018 hepatitis B guidance, Hepatology (AASLD) (2018)
  3. Guidelines for the prevention, diagnosis, care and treatment for people with chronic hepatitis B infection, World Health Organization (2024)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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