The liver is your body’s largest internal organ, weighing roughly 930 grams (about two pounds), and it sits in the upper right side of your abdomen, tucked beneath the ribcage. More than 500 vital functions have been identified with the liver, according to Johns Hopkins Medicine, making it one of the hardest-working organs you have. Its jobs range from filtering your blood to producing proteins, storing energy, and helping you digest fat.
Blood Sugar Regulation
One of the liver’s most critical jobs is keeping your blood sugar stable. After you eat a meal, your blood sugar rises, and the hormone insulin signals the liver to pull glucose out of the bloodstream and store it as glycogen, a compact energy reserve. The liver essentially acts like a battery, charging up when fuel is abundant.
Between meals or overnight, the process reverses. Insulin levels drop, and another hormone called glucagon tells the liver to break its glycogen stores back into glucose and release it into the blood. This keeps your brain and red blood cells fueled even when you haven’t eaten in hours. If glycogen stores run low, the liver can also build entirely new glucose molecules from smaller building blocks like amino acids and lactate, a process called gluconeogenesis. This two-way system is why people with severe liver disease can develop dangerously unstable blood sugar.
Filtering Toxins From Your Blood
Every substance you swallow, inhale, or absorb through your skin eventually passes through the liver. The organ neutralizes harmful compounds in a two-step process. In the first step, a family of specialized enzymes (the cytochrome P450 system) chemically alters toxins through oxidation or reduction, essentially cracking open the molecule so the body can work on it. This includes medications, alcohol, and environmental pollutants.
In the second step, the liver attaches a water-friendly tag to these altered molecules, making them soluble enough to be flushed out through urine or bile. Without this tagging system, fat-soluble toxins would accumulate in your tissues indefinitely. This is also how your liver processes most prescription and over-the-counter drugs, which is why medications that are safe at normal doses can become dangerous in excess or when liver function is compromised.
Producing Proteins Your Blood Needs
The liver manufactures many of the proteins circulating in your bloodstream. The most abundant is albumin, which your liver produces at a rate of 10 to 15 grams per day. Albumin serves two key purposes: it maintains the fluid balance between your blood vessels and surrounding tissues by generating osmotic pressure, and it acts as a transport vehicle, carrying hormones, fatty acids, and drugs through the bloodstream. When albumin levels drop because of liver damage, fluid leaks out of blood vessels and pools in the abdomen or legs, causing visible swelling.
The liver also produces clotting factors, the proteins responsible for stopping bleeding when you cut yourself. Doctors often measure both albumin levels and clotting time together as a quick snapshot of how well the liver is functioning. If either one is off, it signals that the liver’s protein-production machinery is struggling.
Making Bile for Fat Digestion
Your liver produces roughly 600 milliliters of bile every day, about two and a half cups. Bile is a greenish-yellow fluid stored in the gallbladder and released into the small intestine when you eat fatty foods. Its main job is emulsification: breaking large fat droplets into tiny ones so digestive enzymes can access them. Think of it like dish soap dispersing grease in water.
Bile salts are amphipathic, meaning one end of the molecule attracts water and the other attracts fat. They surround fat droplets, and because the water-attracting ends carry negative charges, the coated droplets repel each other and stay small. Without bile, your body would struggle to absorb dietary fats and the fat-soluble vitamins A, D, E, and K. This is why people with bile duct blockages often develop vitamin deficiencies and pale, greasy stools.
Storage and Vitamin Processing
Beyond glycogen, the liver stores iron, copper, and several vitamins. It holds a reserve of vitamins A, D, B12, and K that can supply the body for weeks or even months. The liver also converts vitamin D into its more active form and activates folate so the body can use it for cell division and DNA repair.
Iron metabolism is another major responsibility. The liver stores excess iron and releases it when your bone marrow needs to produce new red blood cells. It also recycles iron from old red blood cells that have reached the end of their roughly 120-day lifespan, processing the leftover hemoglobin into bilirubin, a waste pigment that gives bile its color and stool its brown hue.
The Liver Can Regrow Itself
The liver is the only internal organ that can regenerate to its original size after major tissue loss. Surgeons can remove 70 to 80 percent of a healthy liver, and the remaining tissue will grow back. Full regeneration to 100 percent of the original volume takes approximately 30 months. This remarkable ability is what makes living-donor liver transplants possible: a healthy person donates a portion of their liver, and both the donor’s remaining tissue and the transplanted piece regrow.
Regeneration depends on the liver being fundamentally healthy, though. Chronic damage from alcohol, viral hepatitis, or sustained fat buildup can replace normal liver cells with scar tissue (fibrosis), which does not regenerate. Once scarring becomes extensive, it progresses to cirrhosis, and the liver loses both its structure and its ability to recover.
What Happens When the Liver Struggles
Fatty liver disease is now the most common liver condition worldwide, affecting an estimated 1.27 billion adults globally as of 2021. It occurs when fat accumulates inside liver cells, often driven by excess body weight, insulin resistance, or high sugar intake. In its early stages it produces no symptoms and is fully reversible, but over years it can progress to inflammation, scarring, and eventually liver failure.
When the liver begins to fail, symptoms reflect the loss of its many functions. Bilirubin, the pigment normally excreted through bile, builds up in the blood and turns the skin and eyes yellow, a sign called jaundice. Fluid accumulates in the abdomen because the liver can no longer produce enough albumin. Toxins that the liver would normally filter, particularly ammonia, reach the brain and cause confusion, disorientation, or sleepiness. Other warning signs include upper right abdominal pain, nausea, a swollen belly, and breath with an unusual musty or sweet odor.
Because the liver performs so many overlapping jobs, losing its function affects nearly every other organ system. Blood sugar swings, uncontrolled bleeding from low clotting factors, poor fat absorption, and toxic buildup can all occur simultaneously. The good news is that the liver is resilient and often recovers when the underlying cause of damage is addressed early, whether that means reducing alcohol intake, managing weight, or treating an infection.