What Is An Albumin Assay And What Does It Measure?

An albumin assay is a blood test that measures the amount of albumin, the most abundant protein in your blood plasma. Albumin is made in the liver, and its main jobs are to keep fluid from leaking out of your blood vessels and to carry hormones, vitamins, and drugs through your body. Doctors order this test to check liver function, kidney function, and nutritional status, often as part of a routine health screening or when symptoms suggest an underlying condition.

What Is Albumin and Why Does Your Body Need It?

Albumin is a protein produced exclusively by the liver. It makes up roughly half of the protein found in your blood plasma. The liver produces about 12 to 15 grams of albumin every day, and the protein stays in your bloodstream for about 20 days before it is broken down and replaced.

Albumin has several critical functions. It maintains what doctors call oncotic pressure. This is the force that keeps fluid inside your blood vessels. Without enough albumin, fluid seeps into surrounding tissues, which causes swelling, known as edema. Albumin also acts as a transport vehicle. It carries fatty acids, bilirubin, calcium, certain hormones, and many medications through the bloodstream to the tissues that need them.

What Is an Albumin Assay and What Does It Measure?

An albumin assay measures the exact concentration of albumin in a sample of your blood. The test is typically done on blood drawn from a vein in your arm. In the laboratory, the sample is analyzed using a method called the bromocresol green (BCG) technique or the bromocresol purple (BCP) technique. Both methods use a dye that binds specifically to albumin and changes color. The intensity of the color change tells the lab how much albumin is present.

The normal range for serum albumin is generally 3.5 to 5.0 grams per deciliter (g/dL). Different laboratories may use slightly different reference ranges, so your results are always interpreted against the specific range of the lab that processed your sample. Values below 3.5 g/dL are considered low, and doctors call this condition hypoalbuminemia.

Why Would a Doctor Order an Albumin Assay?

Doctors order an albumin assay for several reasons. It is a standard part of a comprehensive metabolic panel (CMP), which is a group of tests that screens for liver and kidney problems. The test is often included in routine annual physicals.

A doctor may also order this test specifically if you have symptoms that suggest a problem. These symptoms include unexplained swelling in your legs, feet, or abdomen; fatigue and weakness that does not improve; jaundice, which is yellowing of the skin and eyes; or unintended weight loss. If you have a known liver condition such as hepatitis or cirrhosis, your doctor will monitor your albumin levels over time to track how well your liver is functioning.

The test is also used to evaluate nutritional status. Because albumin levels reflect the body’s protein stores, a low level can indicate malnutrition. This is particularly relevant in hospitalized patients, older adults, or people with conditions that affect food absorption, such as Crohn’s disease or celiac disease.

What Does a Low Albumin Level Mean?

A low albumin level is not a diagnosis in itself. It tells your doctor that something is affecting your body’s ability to produce or retain albumin. The causes fall into several categories.

Liver disease is the most direct cause. Since the liver makes albumin, any condition that damages liver cells can reduce production. Chronic liver diseases such as cirrhosis, hepatitis B, hepatitis C, and alcoholic liver disease all lower albumin levels. In advanced liver failure, albumin levels can drop significantly.

Kidney disease can also cause low albumin. Healthy kidneys filter waste from the blood but keep large proteins like albumin inside the bloodstream. When the kidney filters are damaged, a condition called nephrotic syndrome, albumin leaks into the urine. The result is low albumin in the blood along with high protein in the urine.

Inflammation and infection lower albumin levels. During an inflammatory response, the body shifts its protein production toward acute-phase proteins like C-reactive protein (CRP) and away from albumin. This is why albumin levels often drop during serious illness, surgery, or chronic inflammatory conditions such as rheumatoid arthritis.

Malnutrition reduces albumin because the liver lacks the raw materials to build the protein. This happens in starvation, severe calorie restriction, or conditions that prevent nutrient absorption. Digestive disorders that cause protein loss through the gut, such as inflammatory bowel disease, can also deplete albumin.

Burns and major injuries cause albumin loss. Severe burns damage the skin, which normally acts as a barrier. Large amounts of protein-rich fluid leak from the damaged skin surface, dropping albumin levels.

What Does a High Albumin Level Mean?

High albumin levels are less common than low levels and are rarely a cause for concern on their own. The most frequent cause is dehydration. When your blood volume is low, the albumin that is present becomes more concentrated. The test result looks high even though your body actually has a normal total amount of albumin. Rehydrating usually brings the level back to normal.

In some cases, a high albumin level can be a sign of a more serious condition. Certain bone marrow disorders, such as multiple myeloma, can produce abnormal proteins that interfere with the test. However, this is uncommon. Your doctor will look at your other test results and symptoms before drawing any conclusions from an elevated albumin level.

How Is the Albumin Assay Interpreted Alongside Other Tests?

An albumin assay is rarely interpreted in isolation. Doctors look at it together with other markers to build a fuller picture of your health.

One of the most useful combinations is the albumin-to-globulin (A/G) ratio. Globulins are the other major group of proteins in your blood, and they include antibodies and transport proteins. The A/G ratio is calculated by dividing your albumin level by your globulin level. A normal ratio is generally between 1.0 and 2.5. An abnormal ratio can point toward specific conditions. A low ratio with low albumin may indicate liver disease or kidney disease. A low ratio with high globulins can indicate chronic inflammation or immune system disorders.

Doctors also compare albumin levels with liver enzyme tests, such as ALT and AST, to determine whether low albumin is caused by active liver damage. In kidney disease, albumin levels are considered alongside urine tests that measure protein leakage. Together, these tests help your doctor identify which organ system is responsible for the abnormal albumin level.

What Happens During the Test?

The albumin assay is a simple blood test. A healthcare professional draws a small sample of blood from a vein, usually in your arm. The procedure takes just a few minutes. There is no special preparation required. You do not need to fast before an albumin test, although fasting may be required if your doctor ordered other tests along with it.

You can eat and drink normally before the test unless your doctor tells you otherwise. Some medications can affect albumin levels, so tell your doctor about every prescription and over-the-counter drug you take. Hormonal medications, including birth control pills and estrogen therapy, can influence results. The risks of the blood draw are minimal and include slight pain, bruising at the needle site, and rarely, lightheadedness.

Can You Raise Low Albumin Levels?

Treatment for low albumin depends entirely on the underlying cause. There is no single dietary supplement or food that reliably raises albumin if your liver or kidneys are failing. If malnutrition is the cause, improving protein intake can help. Good dietary sources of protein include eggs, lean meat, fish, dairy, beans, and lentils. A registered dietitian can help you plan meals that meet your protein needs.

If liver disease is the cause, treatment focuses on managing the liver condition itself. This may involve antiviral medications for hepatitis, stopping alcohol consumption, or other disease-specific treatments. In severe cases of advanced liver disease, albumin can be given intravenously. This is a medical treatment used in hospitals for specific complications, not something you can do at home.

If kidney disease is the cause, treatment targets the kidney condition. Medications such as ACE inhibitors or angiotensin receptor blockers are commonly prescribed to reduce protein leakage in the urine. Dietary changes, including limiting salt and sometimes protein, may be recommended depending on the stage of kidney disease.

For inflammation-related low albumin, treating the underlying inflammatory condition is the primary goal. Once the inflammation resolves, albumin levels typically return to normal on their own.