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Understanding the Liver: Entire Lesson

for Veterans and the Public

Liver Basics: Entire Lesson

Overview of the liver

Your liver is one of the largest and most important organs in your body. You have only one liver. It is the size of a football and weighs about 3 pounds in the average-size person. It is reddish-brown. Your liver is located on the right side of your abdomen behind your lower ribs, and your ribs help to protect your liver.

The liver behind the lower ribs

The liver is a filter

Your liver has many important jobs. One of the jobs that the liver does is to act as a "filter" for your body. The liver filters or detoxifies the blood.

Almost all the blood in your body passes through the liver. As blood passes through the liver, it breaks down substances, such as prescription or over-the-counter drugs, street drugs, alcohol, and caffeine.

Our bodies naturally produce some harmful (toxic) chemicals or poisons, and those are also broken down by the liver. In this way the liver acts as a filter to clean your blood.

Picture: Liver is a toxin filter

Scroll over image to see an animation of the liver breaking down toxins.

The liver is a factory

The liver is also a "chemical factory" -- performing over 500 chemical functions in your body! The liver takes certain materials in your body and turns them into something else. For example, your liver turns proteins and sugars into things that your body needs.

The liver produces blood-clotting factors that are needed to help you heal after an injury.

It also stores vitamins, hormones, cholesterol, and minerals. Your liver lets go of these chemicals and nutrients when your body needs them, and they flow into your bloodstream.

The liver also produces a greenish fluid called bile. Tubes, called "bile ducts," connect the liver and another organ, the gallbladder, to the small intestine. The bile that is made by the liver helps to digest fats in the small intestine.

Summary of liver functions

The liver:

  • Filters your blood
  • Makes proteins, including blood-clotting factors (needed to help you heal)
  • Stores vitamins, sugars, fats, and other nutrients
  • Helps regulate hormones
  • Releases chemicals and nutrients into the body when needed
  • Makes bile needed for digesting fats
  • And much more

Liver disease and other complications

Liver disease is caused by damage to the liver. Liver damage can be caused by many things, including:

  • Viruses (such as the hepatitis viruses)
  • Drinking alcohol heavily
  • Being very overweight
  • Certain medications--for example, acetaminophen (Tylenol), can cause severe liver damage in people who also have heavy alcohol use
  • Exposure to industrial chemicals, including cleaning solvents, aerosolized paints, and paint thinners

Liver damage can lead to livers that are swollen, shrunken, hard, or scarred. Such livers do not work well, and you can get very sick, or even die, if your liver stops working altogether.

Symptoms of liver disease


If something happens to the liver suddenly, it is "acute." Some acute liver problems will cause symptoms suddenly as well. Symptoms of acute liver disease can include:

  • Tiredness or weakness
  • Jaundice (yellowing of the eyes and skin)
  • Fever
  • Nausea and vomiting
  • Dark urine or very pale colored stools
  • Pain under the ribs on the right side

Up to half of all people with acute liver disease have no symptoms at all. Some types of acute liver disease get better without treatment, and the liver heals itself entirely. On rare occasions an acute liver injury can require hospitalization and even liver transplant right away.


If something is continuing to affect the liver over time, after 6 months it is "chronic." Many people with chronic liver problems will have no symptoms at all and may not even know they have a liver problem. Sometimes they develop symptoms only when the liver has been damaged for many years.


The word "hepatitis" means inflammation or swelling of the liver. Many things can trigger this, and the hepatitis C virus is just one of them. Medications, alcohol, and even some genetic diseases can cause inflammation. (Genetic diseases are ones that are passed down from your biological parents.)

Sometimes liver inflammation gets better on its own, but sometimes, as in the case of chronic hepatitis C, treatment with medications is required to stop the inflammation.

If you have hepatitis, you need to be very careful not to do things that might irritate your liver even more. Alcohol irritates the liver, even in someone who doesn't have any other liver problems.


"Hepatitis" means inflammation of the liver. It can be caused by:

Fibrosis and cirrhosis

Anything that damages the liver over many years can lead the liver to form scar tissue. Fibrosis is the first stage of liver scarring.

When scar tissue builds up and takes over most of the liver, this is a more serious problem called cirrhosis (pronounced "sir-o-sis"). Scar tissue cannot perform any of the jobs of normal liver cells, and this causes a person with cirrhosis to slowly become ill.

Not everyone with hepatitis or a chronic liver problem will develop cirrhosis. Cirrhosis does not happen overnight. In the early years of having cirrhosis, many people will have no obvious signs or be ill and many may not even be aware they have cirrhosis at all.

Cirrhosis can be caused by anything that damages the liver after years of irritation, not just alcohol. However, heavy alcohol use and having the hepatitis C virus for a long time (such as 20 to 30 years) increases your risk.

Liver changes from healthy to cirrhotic.

Scroll over image to see an animation of the liver changing from a healthy liver to a liver with cirrhosis.

Over time, cirrhosis can lead a person to become ill. Symptoms can include fatigue, difficulty thinking clearly, fluid in the abdomen, bleeding in the intestines, and poor blood clotting. Anyone who has cirrhosis, with or without symptoms, needs very close medical attention.

Alcoholic liver disease

Alcoholic liver disease is a common form of liver disease in the United States. People get alcoholic liver disease by drinking large amounts of alcohol for many years. It doesn't matter whether the alcohol comes from hard liquor, beer, or wine. Any type of alcohol can cause liver damage.

One unit of an alcoholic beverage contains 10 grams of alcohol. A unit is roughly equivalent to:

  • one 12-ounce bottle of beer (5% alcohol)
  • one 4-ounce glass of wine (12% alcohol)
  • one 1-ounce shot of hard liquor (40% alcohol)

So how much alcohol is too much? It depends on whether you're a man or a woman. Studies have shown that women experience liver disease at lower levels of alcohol intake than men.

Many liver specialists would agree that liver disease is likely at these levels:

  • For women: 4 or more units of alcohol daily for at least a year
  • For men: 6 or more units of alcohol daily for at least a year

Some people will experience liver damage even if they drink much less. The good news is that the livers of heavy drinkers can improve if they stop drinking entirely.

Fatty liver

Fatty liver is the buildup of fat in liver cells. It is probably the most common type of liver disease in the United States. Fatty liver by itself rarely leads to severe liver damage.

Fatty liver can result from drinking too much alcohol. It can also happen in people who rarely drink. In this case, it is called "nonalcoholic fatty liver disease" or "nonalcoholic steatohepatitis," or NASH. ("Steato-" means fat.) With NASH, a patient's liver shows some inflammation that in some cases can lead to liver damage and cirrhosis (scarring of the liver tissue).

It is not clear why fat builds up in the liver, but people are more likely to develop the condition if they have diabetes, are overweight, or have high levels of cholesterol or blood fats (called "triglycerides"). The amount of fat in the liver may decrease when overweight people lose weight, when diabetics have well-controlled blood sugars, and when cholesterol and triglyceride levels are lowered.

Liver cancer

Like all other body organs, your liver can get cancer. Liver cancer is a disease in which some of the cells in your liver begin to reproduce faster than they should. This can lead to liver tumors, which are generally diagnosed by taking pictures of the liver with ultrasound, computerized tomography (CT) scan, or magnetic resonance imaging (MRI).

Having hepatitis B or hepatitis C can increase your chances of getting liver cancer, called hepatocellular carcinoma (or "HCC").

Most people with liver cancer do not have any symptoms from it early on. Those who do have symptoms often have some pain in the area of their liver (right side of the abdomen, under the ribs), or they may have a build-up of fluid in their abdomen (called "ascites").

Liver cancer is very serious and can be deadly. If you find out that you have liver cancer, you need to get treated as soon as possible.

For more information, go to Liver Cancer.

Other liver diseases

Some genetic disorders cause the liver to build up toxic substances. These include:

  • Hemochromatosis (too much iron)
  • Wilson's disease (too much copper)

Other less common liver diseases include:

  • Autoimmune hepatitis (the body attacks its own liver cells)
  • Primary sclerosing cholangitis (the liver's large bile ducts become blocked, leading to infection, jaundice, and eventual cirrhosis)
  • Primary biliary cirrhosis (liver's small bile ducts become inflamed and bile backs up, leading to itchy skin, jaundice, and eventual cirrhosis)

Liver transplants

Liver transplants are considered only when a patient might die from liver disease. This is sometimes the case when a patient has liver cancer or when someone has advanced liver disease and the liver has stopped functioning properly. Being considered for a liver transplant does not mean that a patient is in danger of dying right away.

Liver transplantation is a long process that involves a lot of medical care. After a transplant, a patient needs lifelong drugs to keep the body from rejecting the new liver, and lifelong follow-up care from a specialist. Survival rates after a transplant are higher than 90% at 1 year, and patients usually have a good quality of life after their recovery.

For more information, go to Liver Transplant tutorial.

Tests for liver damage

Most people with chronic liver disease will have no ongoing symptoms, and the damage will be detected only by blood tests. The tests (called a "liver panel") measure:

  • your level of liver enzymes (see next section)
  • your level of bilirubin (pronounced "billy-roo-bin"), which rises when the liver is not working well
  • a protein called albumin (pronounced "al-byoo-min"), whose levels go down when the liver is damaged

Doctors can run more blood tests if they need to in order to find out what is causing the damage to your liver.

Ultrasound, CAT scans, and MRI are the 3 main methods of taking pictures of the liver. They can often show if the liver injury has become serious. A liver biopsy, in which a needle is used to take a sample of the liver itself, can tell even more about the liver's health.

Some people with liver problems can have a swollen liver. Others may have severe scarring or a shrunken liver. During an examination, a doctor can feel the liver to find out if it is shrunken, hard, or swollen.

For details on laboratory tests, go to Understanding Lab Tests

Liver enzymes

Enzymes are proteins found in your body that speed up certain chemical reactions. Liver enzymes perform these jobs within the liver. Two of the common ones are known as "AST" and "ALT."

If the liver is damaged, AST and ALT pass into the bloodstream. When your doctor looks at the results from your blood tests, AST and ALT values are higher than normal if your liver is damaged.

The damage to the liver can come from viruses, such as the hepatitis C virus, over-the-counter drugs, and prescription and street drugs. If your VA doctor starts you on a certain medication, he or she may need to monitor your blood chemistries to make sure the medication is not causing further harm to your liver.

signs of an unhealthy liver

Scroll over image to see an animation of liver enzymes leaking into the blood.

Results of liver enzyme tests

Low level of liver enzymes in blood:

Usually, this means the liver is healthy. However, a patient may have normal liver enzymes levels but still have liver damage.

Higher than normal level of liver enzymes in blood:

This can mean the liver is unhealthy. Patients also can have higher than normal liver enzyme levels related to problems in other organs, such as their bile ducts.

Reversing liver damage

The liver is one of the only organs in the body that is able to replace damaged tissue with new cells rather than scar tissue. For example, an overdose of acetaminophen (Tylenol) can destroy half of a person's liver cells in less than a week. Barring complications, the liver can repair itself completely and, within a month, the patient will show no signs of damage.

However, sometimes the liver gets overwhelmed and can't repair itself completely, especially if it's still under attack from a virus, drug, or alcohol. Scar tissue develops, which becomes difficult to reverse, and can lead to cirrhosis.

Keeping your liver healthy

Here are some things to remember about keeping your liver healthy:

  • Don't have unsafe sex (always use condoms).
  • Don't inject drugs like heroin or cocaine.
  • Don't drink alcohol. Alcohol is a poison to the liver and also can make liver diseases such as hepatitis much worse. If you do drink, drink lightly.
  • Don't share any personal items such as razors or toothbrushes that might have blood on them.
  • Ask your VA doctor about getting vaccinated against hepatitis A and B. There is currently no vaccine against the hepatitis C virus.
  • Follow strict food safety guidelines. Make sure that the water you drink and the food you eat are clean, especially when traveling to other countries. Most cases of infection with hepatitis A result from poor cleanliness during food preparation.
  • If you take any medications, make sure your doctor knows about them. Also tell your doctor about any over-the-counter medicines, supplements, and natural or herbal remedies that you use. Certain medicines taken at the same time can cause damage to your liver, even if you can buy them without a prescription.
  • Maintain a healthy body weight.
  • Control blood sugars if you have diabetes.
  • Keep cholesterol and blood fats within the recommended range. Ask your VA health care provider for advice on doing this.

Keeping your liver healthy when you have hepatitis

Here are some things to remember about keeping your liver healthy if you have viral hepatitis (hepatitis B or C):

  • Don't drink alcohol. Alcohol can cause further swelling and irritation of your liver, and drinking increases your chances of cirrhosis. No one knows if there is a safe amount of alcohol for patients with liver disease.
  • Get tested for hepatitis A. A blood test can tell if you are already immune to hepatitis A. If you have hepatitis B or C, and you are not immune to hepatitis A, you should get vaccinated for hepatitis A. If you have hepatitis B or C or any other chronic liver disease, you have a higher chance of getting very sick if you get hepatitis A.
  • If you have hepatitis C, you should also be tested for hepatitis B. The test can tell if you have ever been exposed to hepatitis B. If you are not already immune to hepatitis B, you should get vaccinated for hepatitis B. Other than having hepatitis C, there are other reasons you may need hepatitis B vaccination, including if:
    • you belong to a group at risk for hepatitis B (such as health care workers)
    • you have been involved in high-risk sexual behavior
    • there is any chance of your using or sharing needles for illegal drug use
  • If you are already immune to hepatitis B, you should be protected from getting it again. If you have hepatitis B, you should also be tested for hepatitis C. The test can tell if you have ever been exposed or have chronic hepatitis C. There is no vaccine to protect against getting hepatitis C, but you should be especially cautious about not being exposed to hepatitis C--for example, by never sharing needles with anyone.
  • If you have: Get tested for: If not immune, get vaccinated for: If you also have:
    Chronic hepatitis B Hepatitis A, Hepatitis C Hepatitis A Chronic hepatitis C - get very carefully monitored
    Chronic hepatitis C Hepatitis A, Hepatitis B Hepatitis A, Hepatitis B Chronic hepatitis B - get very carefully monitored
  • Be careful with medications. Occasional use of low-dose acetaminophen (commonly known as Tylenol) is OK. A general rule is to take half the dose recommended on the bottle. No more than 500 mg at a time and no more than 2,000 mg (4 tablets) in a 24 hr period. It is also OK to take ibuprofen (Motrin or Advil) if you do not have cirrhosis. Regular aspirin is fine if it doesn't bother your stomach.
  • Be careful about vitamins and minerals. Avoid iron supplements unless prescribed by your doctor. Iron might speed up the process of liver scarring, particularly when taken in large doses.
  • Be careful about herbal remedies. Some patients ask to take the herb "milk thistle," believing it can reduce swelling in the liver. Whether milk thistle works or not is unknown. However, be cautious when taking any herb. U.S. regulations do not require that these products be tested for quality.


Products and Publications

  • The ABCs of Hepatitis
    Two-page guide to the symptoms, treatment, and prevention of hepatitis A, B, and C
  • ABCs of Hepatitis (video)
    This 15-minute video was created for general education on hepatitis A, B, and C in substance use disorder programs.Transcript included.
  • Drinking Diary and Change Plan
    Wallet card for patients to record their alcohol use over a 4-week period as a way to monitor and reduce their drinking behavior.
  • Glossary
    Definitions of terms commonly used with viral hepatitis and related conditions.

Web Resources

  • American Liver FoundationLink will take you outside the VA website. VA is not responsible for the content of the linked site.
    A national nonprofit organization dedicated to the prevention, treatment, and cure of hepatitis and other liver diseases through research, education, and advocacy. Web site features a database directory of hepatitis clinical trials, lay-oriented facts sheets, and links to additional resources.
  • Centers for Disease Control and Prevention: Viral HepatitisLink will take you outside the VA website. VA is not responsible for the content of the linked site.
    Information on all types of viral hepatitis from the CDC's National Center for Infectious Diseases. Site features related CDC guidelines and recommendations as well as training materials, slide sets, fact sheets, and key CDC hepatitis documents.
    • Hepatitis Risk AssessmentLink will take you outside the VA website. VA is not responsible for the content of the linked site.
      5-minute assessment developed by the federal Centers for Disease Control and Prevention that gives you a personalized report of your hepatitis risk
  • NATAP: HepatitisLink will take you outside the VA website. VA is not responsible for the content of the linked site.
    Recogizing that coinfection with viral hepatitis among people with HIV is a growing problem, the National AIDS Treatment Advocacy Project (NATAP) has developed an extensive amount of information on hepatitis, both in the context of HIV coinfection and as a separate illness. NATAP provides coverage of key conferences, maintains a selection of hepatitis articles, and features an ask-the-expert forum on hepatitis C.