Hepatitis B is a virus that infects the liver and spreads through blood and body fluids
Hepatitis B is caused by the hepatitis B virus (HBV). The virus lives in blood and certain body fluids. It enters your body through a break in the skin or mucous membranes—a cut, a needle stick, or contact with infected blood or semen. Once inside, it travels to your liver and begins to multiply. Some people clear the infection on their own within six months. Others develop chronic hepatitis B, meaning the virus stays in their body for life and can damage the liver over decades.
You cannot catch hepatitis B by sharing food, shaking hands, hugging, coughing, sneezing, or sharing utensils. It does not spread through saliva alone. The virus needs direct access to the bloodstream.
Key Takeaways
- Hepatitis B spreads through blood and body fluids, not through casual contact or food.
- Some people recover from hepatitis B infection within six months; others develop a lifelong infection that can lead to liver scarring or cancer.
- A vaccine prevents hepatitis B and is part of routine childhood immunizations in most countries.
- Many people with chronic hepatitis B have no symptoms for years, so testing is the only way to know your status.
- Antiviral medications can slow or stop liver damage even if you cannot clear the virus completely.
How hepatitis B spreads from person to person
The virus enters your bloodstream. The most common routes are unprotected sex with an infected partner, sharing needles or injection equipment, needle stick injuries in healthcare settings, and transmission from mother to baby during birth. Hepatitis B can also spread if you have cuts or sores in your mouth and share a toothbrush with someone who is infected, though this is less common.
Healthcare workers, people who inject drugs, and people with multiple sexual partners face higher risk. Infants born to mothers with hepatitis B are at very high risk of developing chronic infection—up to 90 percent of infected newborns will carry the virus for life, compared to about 5 to 10 percent of infected adults.
The difference between acute and chronic hepatitis B
Acute hepatitis B is a short-term infection. Your immune system fights off the virus, and you recover within six months. You may have no symptoms at all, or you may develop fatigue, jaundice (yellowing of the skin and eyes), abdominal pain, and dark urine. Once you recover, you cannot catch hepatitis B again—you have immunity.
Chronic hepatitis B means the virus stays in your body longer than six months. Your immune system cannot clear it completely. Many people with chronic infection have no symptoms for 10, 20, or even 30 years. During that time, the virus is quietly damaging liver cells. Over decades, chronic hepatitis B can lead to cirrhosis (severe scarring of the liver), liver failure, or liver cancer. Not everyone with chronic infection develops these complications, but the risk is real.
Symptoms you might notice, and when they appear
Acute hepatitis B symptoms usually appear two to three months after infection, though the range is six weeks to six months. They include fatigue, joint pain, abdominal pain, loss of appetite, nausea, and jaundice. Some people have no symptoms at all and only discover they were infected if they donate blood or have a test for another reason.
Chronic hepatitis B often causes no symptoms for years. You may feel fine while the virus damages your liver. This is why people at risk—healthcare workers, people with multiple partners, people who inject drugs, and household contacts of infected people—should be tested even if they feel well. By the time symptoms appear (swelling in the legs or belly, confusion, vomiting blood), liver damage is often advanced.
Testing and diagnosis
A blood test is the only way to know whether you have hepatitis B. The test looks for hepatitis B surface antigen (HBsAg), a protein on the virus's outer layer. If that test is positive, a second test checks for hepatitis B core antibody (anti-HBc) to confirm infection. Additional tests measure how much virus is in your blood and whether your liver is already damaged.
If you test positive, your doctor will likely order an ultrasound or a test called FibroScan to check for scarring. These tests help determine how much liver damage has already occurred and whether you need treatment now or should be monitored over time.
Treatment options and what they do
There is no cure for chronic hepatitis B, but antiviral medications can slow or stop the virus from multiplying and damaging your liver. Common medications include tenofovir and entecavir. These drugs do not eliminate the virus, but they can prevent cirrhosis and reduce the risk of liver cancer if you take them consistently.
Not everyone with chronic hepatitis B needs treatment immediately. Your doctor will consider how much virus is in your blood, whether your liver shows signs of damage, and your age. Some people are monitored with regular blood tests and ultrasounds for years before treatment begins. Others start medication right away. The goal is to prevent liver failure and cancer while minimizing side effects from long-term medication use.
Vaccination and prevention
The hepatitis B vaccine prevents infection and is highly effective. It is given as a series of shots—usually three doses over six months, though some formulations require four doses. The vaccine is part of routine childhood immunizations in most countries. Adults at risk—healthcare workers, people with multiple sexual partners, people who inject drugs, and household contacts of infected people—should also be vaccinated if they have not been already.
If you are exposed to hepatitis B (through a needle stick, unprotected sex, or other means), a shot called hepatitis B immunoglobulin (HBIG) given within 24 hours, combined with the vaccine series, can prevent infection. This is why healthcare workers report needle stick injuries immediately.
Living with chronic hepatitis B
If you have chronic hepatitis B, you can live a normal lifespan with proper monitoring and treatment. You should not donate blood, organs, or tissue. You should tell sexual partners about your status so they can be vaccinated and take precautions. If you are pregnant, tell your doctor—your baby can be protected with vaccination and immunoglobulin at birth.
Avoid alcohol, which speeds liver damage. Maintain a healthy weight and eat a balanced diet. Get vaccinated against hepatitis A (a separate virus that can cause severe illness in people with hepatitis B). Have regular check-ups with a doctor who specializes in liver disease. Many people with chronic hepatitis B live for decades without developing serious complications, especially if they start treatment early.
Frequently Asked Questions
Can you catch hepatitis B from sharing a drink or eating utensils?
No. Hepatitis B virus does not survive in saliva and cannot pass through the digestive system. You would need the virus to enter your bloodstream directly. Sharing food, drinks, or utensils is safe.
If I test positive for hepatitis B, does that mean I will definitely get liver cancer?
No. Many people with chronic hepatitis B never develop liver cancer or cirrhosis, especially if they start treatment early or have a strong immune response. Regular monitoring and antiviral medication reduce the risk significantly. Your doctor can estimate your individual risk based on blood tests and imaging.
How long does it take to know if you have acute or chronic hepatitis B?
Doctors typically wait six months after initial infection to determine this. If the virus is still in your blood after six months, it is chronic. If it has cleared, you had acute hepatitis B and have recovered.
Can someone with hepatitis B have children?
Yes. If you are pregnant and have hepatitis B, your baby can be protected with vaccination and immunoglobulin at birth. If your partner has hepatitis B, you can be vaccinated before trying to conceive. With these precautions, the risk of transmission is very low.
What should I do if I think I was exposed to hepatitis B?
Contact a doctor or urgent care clinic immediately. If it has been less than 24 hours since exposure, you may be given hepatitis B immunoglobulin and the vaccine series to prevent infection. The sooner you seek care, the better the protection.