Dozens of conditions can damage the liver, but they fall into a handful of major categories: fatty liver disease, viral hepatitis, alcohol-related damage, autoimmune disorders, genetic conditions, and cancer. Fatty liver disease alone affects more than 30% of the global population, making it the single most common liver condition worldwide. Understanding these diseases matters because many of them share a quiet early phase, progressing silently toward scarring and serious complications before symptoms ever appear.
Fatty Liver Disease (MASLD)
The most widespread liver disease in the world was long known as nonalcoholic fatty liver disease, or NAFLD. In 2023, an international consensus renamed it metabolic dysfunction-associated steatotic liver disease (MASLD) to better reflect what actually drives it: metabolic problems like insulin resistance, obesity, high blood pressure, and abnormal cholesterol. The new name also drops the “nonalcoholic” label, which many patients and clinicians found stigmatizing and imprecise.
MASLD begins when fat accumulates inside liver cells. For many people, this fatty buildup causes no obvious harm and no symptoms. But in a subset of patients, the fat triggers ongoing inflammation, a stage now called metabolic dysfunction-associated steatohepatitis (MASH, formerly NASH). MASH can gradually replace healthy liver tissue with scar tissue, eventually leading to cirrhosis or liver cancer. Among people aged 15 to 49, the number of prevalent cases nearly doubled between 1990 and 2021, rising from roughly 343 million to 666 million globally. Obesity and type 2 diabetes are the strongest risk factors, and both continue to rise in most countries.
Viral Hepatitis
Five viruses, labeled A through E, specifically target the liver. They differ sharply in how they spread and how much long-term damage they cause.
Hepatitis A and hepatitis E spread through contaminated food or water. Both typically cause a short-term illness with fatigue, nausea, abdominal pain, and sometimes jaundice. Most people recover fully without lasting liver damage.
Hepatitis B and hepatitis C are the heavy hitters. Together, they are the most common cause of liver cirrhosis and liver cancer worldwide. Hepatitis B spreads through blood, sexual contact, and from mother to infant during birth. It can also pass between family members in early childhood. Hepatitis C spreads primarily through blood exposure, including shared needles, contaminated medical equipment, and less commonly through sexual contact. Both viruses can become chronic infections that silently damage the liver over years or decades. Roughly half of all liver cancers globally are linked to hepatitis B, and another quarter to hepatitis C.
Hepatitis D only infects people who already carry hepatitis B. When the two viruses combine, the resulting liver disease tends to be more severe and progress faster than hepatitis B alone.
Alcohol-Related Liver Disease
Heavy drinking damages the liver in a predictable sequence. First comes fatty liver, which is reversible if drinking stops. Continued drinking can trigger alcoholic hepatitis, an inflammatory stage that causes fever, jaundice, and abdominal pain. If heavy use persists, the liver develops permanent scarring.
A large population-based study found that drinking more than roughly 12 standard units per week (about 92 grams of pure alcohol) significantly increases the risk of developing liver disease. For context, a standard glass of wine or a regular beer each contain roughly one standard unit. The risk climbs steadily with intake, and daily consumption of 40 to 60 grams of alcohol is strongly associated with liver cancer. Not everyone who drinks heavily develops liver disease, but alcohol remains one of the leading causes of preventable liver damage globally.
Autoimmune Liver Diseases
In autoimmune liver diseases, the immune system mistakenly attacks the liver’s own tissue. The two most recognized forms target different structures within the liver.
Autoimmune hepatitis attacks liver cells directly, causing inflammation that can range from mild to severe. It affects women more often than men and can appear at any age. Without treatment, it can progress to cirrhosis relatively quickly.
Primary biliary cholangitis (PBC) targets the small bile ducts inside the liver. As these ducts are slowly destroyed, bile backs up and damages surrounding tissue. Most people with PBC test positive for a specific immune marker called antimitochondrial antibody, which helps distinguish it from other liver conditions. Early symptoms often include persistent itching and fatigue, sometimes years before jaundice or other signs of liver damage develop.
Genetic and Inherited Conditions
Several inherited disorders cause the liver to accumulate substances it cannot properly process. The two most important are hemochromatosis and Wilson’s disease.
Hereditary hemochromatosis results from a mutation on chromosome 6 that causes the body to absorb too much iron from food. Over time, iron builds up in the liver, heart, and pancreas, leading to organ damage. It is one of the most common genetic disorders in people of Northern European descent. When caught early, treatment is straightforward: regular blood removal (similar to donating blood) keeps iron levels in check and prevents organ damage.
Wilson’s disease involves a mutation on chromosome 13 that impairs the liver’s ability to excrete copper into bile. Copper accumulates first in the liver and then in the brain, eyes, and other organs. It typically appears in childhood or young adulthood. Left untreated, both hemochromatosis and Wilson’s disease cause rapidly progressing organ damage and can be fatal. With early diagnosis, both are highly manageable.
Other, less common inherited conditions that affect the liver include alpha-1 antitrypsin deficiency, glycogen storage diseases, and certain chronic cholestatic syndromes.
Liver Cancer
Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer, and it rarely develops in a healthy liver. The major risk factors are chronic hepatitis B, chronic hepatitis C, heavy alcohol use, and fatty liver disease. Obesity and diabetes independently raise the risk as well. In parts of Asia and Africa, aflatoxin, a toxin produced by mold that contaminates stored grains and peanuts, is a significant additional cause.
Because HCC almost always arises in a liver that is already damaged, people with cirrhosis from any cause are typically monitored with regular imaging. The stage at which cancer is detected has a large influence on treatment options and outcomes. Early-stage tumors found through screening can sometimes be surgically removed, while more advanced disease requires other approaches.
How Liver Disease Is Detected
Most liver diseases share the same frustrating feature: they produce few or no symptoms until significant damage has occurred. The earliest signs, when they appear at all, tend to be nonspecific. Fatigue, mild nausea, or a dull ache in the upper right abdomen are easy to dismiss. Jaundice, the yellowing of the skin and the whites of the eyes, develops when bilirubin (a waste product normally cleared by the liver) accumulates in the blood. It becomes visible once blood levels rise above about 2 mg/dL. Persistent itching, particularly without a rash, can be another signal of bile flow problems in the liver.
Routine blood tests called liver function tests are the most common screening tool. The key markers include ALT (normal range 7 to 55 U/L), AST (8 to 48 U/L), ALP (40 to 129 U/L), and bilirubin (0.1 to 1.2 mg/dL). Elevated levels don’t point to a specific disease, but they signal that something is stressing or damaging liver cells and that further investigation is needed.
How Liver Disease Progresses to Cirrhosis
Regardless of the original cause, chronic liver damage follows a common path. Repeated injury triggers inflammation, which leads to fibrosis (scar tissue replacing healthy tissue). When fibrosis becomes extensive, the liver reaches a stage called cirrhosis.
Cirrhosis has two distinct phases. In the compensated phase, the liver is scarred but still functional enough to perform its essential jobs. Most people in this phase have no symptoms and may not know they have cirrhosis at all. Each year, roughly 5% to 7% of people with compensated cirrhosis transition to the decompensated phase, where the liver can no longer keep up. Fluid buildup in the abdomen (ascites) is typically the first sign of decompensation. Other complications include bleeding from swollen veins in the esophagus and confusion caused by toxins the liver can no longer filter, known as hepatic encephalopathy.
Once decompensation occurs, the disease is considered permanently advanced. The underlying mechanisms that caused the breakdown persist even if the triggering event is addressed. This is why catching liver disease early, before cirrhosis develops, dramatically changes the outlook. Many of the conditions described above are treatable or manageable when identified in their earlier stages.