Understanding hepatitis B: Symptoms, causes, and treatment

Hepatitis B is caused by the hepatitis B virus (HBV) and can affect people of any age worldwide. The infection may be acute and short-lived or become chronic, which increases the risk of liver scarring (cirrhosis) and liver cancer over time. Because many infections are silent at first, understanding symptoms, routes of transmission, diagnostic tests, and treatment choices helps individuals and communities reduce harm and protect liver health.

This article is for informational purposes only and should not be considered medical advice. Please consult a qualified healthcare professional for personalized guidance and treatment.

Symptoms of hepatitis B

Most adults with acute hepatitis B develop symptoms one to four months after exposure, though many remain asymptomatic. Early signs can resemble a flu-like illness: fatigue, fever, loss of appetite, nausea, vomiting, and muscle or joint aches. As liver inflammation increases, some people notice right upper abdominal discomfort, dark urine, pale or clay-colored stools, and yellowing of the skin or eyes (jaundice). Itching and a general feeling of malaise are also common. Children, especially infants, often have few or no symptoms even when infected. Severe but uncommon presentations include confusion, easy bruising or bleeding, and extreme drowsiness, which can signal acute liver failure and require urgent medical attention.

Causes of hepatitis B virus infection

HBV spreads through contact with infected blood and certain body fluids. Common routes include unprotected sexual contact, sharing needles or syringes, and needlestick injuries in healthcare or similar settings. Transmission from a pregnant person to a baby can occur during birth without appropriate preventive measures. Household exposure may happen through shared items that can carry microscopic blood, such as razors or toothbrushes. In settings with robust blood screening, transfusion-related transmission is rare, but in some regions it remains a concern. HBV is not spread by casual contact like hugging, sharing food, or coughing. People at higher risk include those with multiple sexual partners, people who inject drugs, individuals undergoing hemodialysis, household or sexual contacts of someone with HBV, and healthcare workers handling sharps. Vaccination, safer sex practices, avoiding needle sharing, and using standard precautions in healthcare are key prevention strategies.

Diagnosis of hepatitis B

Diagnosis relies on blood tests that detect viral proteins and antibodies, often alongside liver enzyme tests. The hepatitis B surface antigen (HBsAg) indicates current infection. The antibody to the surface antigen (anti-HBs) indicates immunity, either from past infection that has resolved or from vaccination. Antibodies to the core antigen (anti-HBc) help determine timing: the IgM form suggests recent or acute infection, while IgG suggests past exposure. The “e” antigen (HBeAg) and HBV DNA quantify active viral replication. A pattern of persistent HBsAg for at least six months usually indicates chronic infection. Clinicians also measure alanine aminotransferase (ALT) and other liver tests to gauge inflammation.

Beyond confirming infection, assessment focuses on disease stage and liver health. Noninvasive scores (such as APRI or FIB-4), elastography (often called FibroScan), and ultrasound can help estimate scarring and guide monitoring. People with chronic infection and increased risk—such as those with cirrhosis or a family history of liver cancer—may undergo regular liver ultrasound and blood tests to screen for complications. Testing is recommended for individuals after possible exposure, during pregnancy, for blood and organ donors, and for people with conditions or treatments that suppress the immune system.

Treatment depends on whether the infection is acute or chronic and on markers of active disease. Most acute infections in adults clear spontaneously with supportive care: rest, hydration, and avoidance of alcohol and medications that stress the liver unless specifically advised by a clinician. Chronic infection management aims to suppress viral replication, reduce liver inflammation, and prevent complications. Common first-line antiviral medicines include tenofovir (disoproxil fumarate or alafenamide formulations) and entecavir. Decisions to start therapy consider HBV DNA level, ALT, presence of HBeAg, degree of fibrosis, age, and coexisting conditions. Some people may not need immediate medication but do need regular monitoring to watch for changes.

Prevention and special situations also matter. The HBV vaccine provides strong protection and is recommended for infants, children, and unvaccinated adults at risk. Newborns of mothers with HBV should receive the first vaccine dose at birth and hepatitis B immune globulin (HBIG) as directed to lower transmission risk. During late pregnancy, antiviral therapy may be considered for those with high viral loads to further reduce the chance of transmission. After a potential exposure—such as a needlestick or sexual exposure—prompt evaluation for post-exposure prophylaxis with vaccine and, in some cases, HBIG can reduce the likelihood of infection. People with chronic HBV are advised to avoid alcohol, discuss any supplements or new medicines with a clinician, and receive appropriate vaccinations for other liver-related risks when indicated.

In summary, hepatitis B ranges from a short-term illness to a chronic condition with long-term consequences. Recognizing how it spreads, the often subtle nature of early symptoms, and the role of targeted testing allows earlier diagnosis. Evidence-based prevention, including vaccination and safe practices, combined with appropriate antiviral therapy and monitoring, can reduce complications and support long-term liver health.