12 Foundational Facts About the Liver

You may not think much of your liver, hidden as it is deep inside your body, unless you over-imbibe at a party. But your liver runs multiple functions on your behalf to keep you healthy. Not only is it your largest internal organ; it is in charge of hundreds of bodily processes ranging from fighting infection to manufacturing proteins and hormones to helping your blood clot.

This reddish brown organ has two lobes, on the right and left, and it hangs out just on top of the gallbladder and next to parts of the pancreas and intestines. Your liver and these neighboring organs work as a team to digest and absorb your food. Its main job is to filter the blood that comes from the digestive tract before it hits the rest of your body. The liver also detoxifies chemicals and metabolizes drugs. As it does so, the liver secretes bile that ends up back in the intestines. The liver also makes proteins important for blood plasma and other functions. With some expert support, here are 12 facts about this under-appreciated organ.

1. The liver has a lot of responsibilities.
2. It’s the second-biggest organ.
3. The liver is both an organ and a gland.
4. It’s full of blood.
5. The first liver transplant was not a great success.
6. The liver is the only organ that can completely regenerate.
7. Your brain depends on a healthy liver.
8. Some liver diseases may show no symptoms.
9. The liver processes prescription drugs and natural supplements the same way.
10. Your weight has bearing on your liver function.
11. It’s a busy bile factory.
12. All vertebrates have one.

The liver has a lot of responsibilities.

The liver is a very complicated organ with a role in nearly every bodily function, according to Dr. Nancy Reau, chief of hepatology and associate director of organ transplantation at Rush University. Some of its jobs include making and storing energy; producing proteins vital for body function; processing drugs—prescriptions, OTCs, and “drugs of abuse”; and playing a vital role in immune function. “Although it’s hard to quantify all of the liver’s many roles, it is easy to see how sick a person becomes when the liver stops functioning,” Reau told Mental Floss in 2017.

It’s the second-biggest organ.

After your skin, the liver is the body’s largest organ. Your liver can weigh up to three pounds, about the same as a small Chihuahua, and it’s about the size of a football. It is located just beneath your rib cage on the right side of your body. If you could feel it, it would be rubbery to the touch.

The liver is both an organ and a gland.

Organs usually have a job specific to one region of the body. Glands are specialized types of organs that remove substances from the blood, alter or process them, then release them to other parts of the body or eliminate them. In that respect, the liver, which filters your body’s toxins (such as drugs and alcohol) and pushes them out of your body, is also a gland.

It’s full of blood.

At its fullest, the liver holds approximately one pint of blood (roughly 13 percent of your total blood). It can pump nearly 1.5 liters of blood through itself per minute.

The first liver transplant was not a great success.

In 1963, when Dr. Thomas E. Starzl performed the first human liver transplant at the University of Colorado Medical School, he had the wrong kinds of immunosuppressive drugs on hand and no patient lived more than a few weeks. However, only four years later, the expansion of available immunosuppressive drugs made the first successful liver transplant possible.

The liver is the only organ that can completely regenerate.

The liver has the incredible ability to completely regrow with as little as 25 percent of the original tissue available. “When a person donates more than half of their liver to someone who needs a transplant, the liver returns to its original size in nearly two weeks,” Reau said. According to a 2009 study in the Journal of Cell Physiology, evolutionary safeguards are responsible for this regenerative effect due to the numerous functions performed by the liver. “This process allows liver to recover lost mass without jeopardizing viability of the entire organism,” the authors write.

Your brain depends on a healthy liver.

The liver is a major regulator of plasma glucose and ammonia levels. If these get out of whack because your liver isn’t functioning properly, toxins can build up in your blood and brain and cause a condition known as hepatic encephalopathy. If it’s not treated, it can be debilitating or even fatal. In other words, if you want your brain to function, you need a working liver.

Some liver diseases may show no symptoms.

Because many liver conditions, from hepatitis to cirrhosis, may have no symptoms in the early stages, “you can even have a serious liver injury when your liver tests are all normal,” Reau said.

The liver processes prescription drugs and natural supplements the same way.

You may think an herbal or dietary supplement that has the word natural on the bottle is safe. But Reau cautions, “Herbs and all-natural therapy [are] processed by the liver in the same way that FDA-approved medications are processed.” It’s best to talk with your doctor if you’re uncertain about taking supplements or what’s actually in them. Although liver injury is uncommon for both prescribed and complementary therapies, being “all natural” does not eliminate all risk.

Your weight has bearing on your liver function.

Your body needs about one gram (0.03 ounces) of liver for every kilogram (35 ounces) of weight in order to effectively do its job, Dr. Neil Mukherjee, a liver surgeon and fellow at Florida Hospital’s Southeastern Center for Digestive Disorders & Pancreatic Cancer, told Mental Floss in 2017.

It’s a busy bile factory.

The liver produces about 700 to 1000 milliliters of the greenish-brownish stuff every day. The bile gathers in little ducts and then moves on to the main bile duct, where it’s carried to the duodenum of the small intestine, either directly or via the gallbladder. Bile is key to your body's ability to break down and absorb fats.

All vertebrates have one.

Every vertebrate—that is, any living being that has a spinal cord—has a liver, a necessary part of survival. The organs all have a similar structure and perform the same essential tasks in animals of every shape and size.

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A version of this story was published in 2017; it has been updated for 2024.