Chemotherapy HBV Risk: What You Need to Know About Liver Health During Cancer Treatment

When you're undergoing chemotherapy, a treatment that uses drugs to kill fast-growing cancer cells. Also known as cancer drug therapy, it saves lives—but it can also wake up hidden viruses in your body. One of the most dangerous surprises is hepatitis B virus, a liver infection that can lie dormant for years without symptoms. Also known as HBV, it’s not rare: over 250 million people worldwide carry it silently. If you’ve had HBV in the past—even if you never felt sick—chemotherapy can trigger a dangerous flare-up called HBV reactivation, a sudden return of active virus replication after being controlled by the immune system. This isn’t just a theoretical risk. Studies show up to 20% of HBV carriers on certain chemo drugs develop severe liver injury, and some even need a transplant—or die from it.

Why does this happen? Chemotherapy weakens your immune system so it can’t keep the virus in check. The same drugs that target cancer cells also shut down your body’s ability to suppress HBV. This isn’t limited to one type of chemo—it happens with drugs used for lymphoma, leukemia, breast cancer, and even some newer immunotherapies. The risk is highest if you’re positive for HBsAg (the surface antigen), but even people who only have anti-HBc antibodies (a sign of past infection) are at risk. That’s why screening isn’t optional. Before starting treatment, doctors should test for HBsAg, anti-HBc, and sometimes anti-HBs. If you’re positive, antiviral drugs like entecavir or tenofovir are started before chemo begins and kept going for months after. These aren’t just add-ons—they’re lifesavers.

Many patients don’t know they have HBV until it flares up during treatment. That’s why even if you’ve never been told you have liver disease, testing is critical. It’s not about blame or past behavior—it’s about biology. The liver doesn’t care why the virus is there; it only reacts to what happens next. And when chemo turns off your immune guard, the virus can multiply fast, causing jaundice, extreme fatigue, or even liver failure. The good news? With proper screening and antiviral protection, HBV reactivation is almost always preventable. You don’t need to avoid chemo. You just need to make sure your care team knows your full medical history and runs the right tests. Below, you’ll find real-world insights from patients and providers who’ve navigated this exact challenge—what worked, what didn’t, and how to stay safe while fighting cancer.