Albumin is a blood protein that delivers vitamins, minerals, and medications all around the body. It is often tested because it can provide important clues about your overall health. Read on to learn more about this important protein, what high and low values mean, and how to improve your health based on your albumin levels.
What is Albumin?
Albumin Definition
Albumin is the most abundant protein in human blood, accounting for 50 to 60% of all the protein in the blood. It’s made by the liver, circulates throughout the body in blood, and a very small amount may pass through healthy kidneys into urine [1].
What Albumin Does and How It Functions
Albumin maintains the osmotic pressure that pulls water into the circulatory system. The pressure inside blood vessels exerted by pumping of the heart (hydrostatic pressure) creates a force to push fluids out of veins and arteries into the surrounding tissue. Albumin prevents this by drawing fluids in due to osmosis.
Albumin binds hormones, vitamins, drugs, fatty acids, minerals, and other substances in the blood, carries them throughout the body, and delivers them to body tissues. Albumin has many locations where substances can attach to.
Albumin is also the main antioxidant in blood. It works by binding with metals and reacting with free radicals, which prevents them from reacting with other parts of the body and causing damage [2].
Albumin Is Different Than Prealbumin
Despite the similarity in the names, prealbumin is not a precursor of albumin. Transthyretin is a more modern name for prealbumin. It’s a completely different protein that is found in human blood, spinal fluid, and inside the eyes. It occurs in lower concentrations in blood than albumin and is primarily responsible for moving thyroid hormones and vitamin A around the body.
Albumin Blood Test
An albumin blood test measures the amount of albumin in the blood. Low albumin is common in many health problems, so albumin levels are often checked in conjunction with other tests to help diagnose diseases, determine if other tests are needed, or to check if treatments for a condition are working. An albumin blood test is a standard part of the following sets of blood tests:
- Comprehensive Metabolic Panel (CMP) for an overall picture of health
- Liver Function Panel to assess inflammation, infection, or liver damage and disease
- Total Protein to check nutrition, general health, or to diagnose liver and kidney diseases
- Renal Panel to diagnose or monitor kidney conditions
Normal Levels
The exact range for normal albumin levels depends on the specific laboratory that performs the blood test, however, it is usually around 3.5 to 5.6 g/dL or 35 to 56 g/L.
Low Albumin
A low albumin level is anything that falls below the normal range as defined by the laboratory performing the test, usually less than 3.5 g/dL or 35 g/L. The condition of having low albumin is called hypoalbuminemia.
However, a result that’s lower than normal, doesn’t necessarily mean that you have a health condition needing treatment. Your doctor will interpret your albumin result, taking into account your medical history, symptoms, and other test results.
Low albumin levels are seen in a wide range of health problems, including diabetes, cancer, and liver disease, and are primarily a result of illness rather than a cause [3].
Albumin levels can be used as a measure of how severe an illness is, with lower levels associated with worse outcomes [4].
Causes of Low Levels
Causes shown here are commonly associated with low albumin levels. Work with your doctor or another health care professional to get an accurate diagnosis.
1) Chronic Illness, Infection, and Inflammation
The most common cause of low albumin is inflammation. When illness or injury occurs, the body responds with inflammation and channels resources into the production of proteins that help defend the body, such as the C-reactive protein (CRP). As the liver increases the production of CRP (and other proteins of the immune system), it decreases the production of albumin [5, 6].
Cancerous tumors cause inflammation, which results in lowered albumin levels. The larger and/or more widespread the tumors, the larger the inflammatory response and the lower albumin levels drop [7].
Low albumin can also be caused by leakage from blood vessels if they are damaged or become more permeable, especially during injury, inflammation, and sepsis [3].
2) Malnutrition
Although malnutrition or inadequate protein consumption was thought to play an important role in low albumin levels (and continues to be cited in popular articles on the topic), more recent research has established that low albumin can occur without malnutrition, and malnourished individuals usually do not have low albumin levels. The exception is Kwashiorkor, a form of protein malnutrition seen in famines that is extremely rare in the developed world [8, 9].
3) Liver Disease
Because albumin is produced in the liver, liver diseases that interrupt albumin production can cause low levels [10, 11].
4) Kidney Disease
In healthy people, the loss of albumin in the urine is minimal. However, when the kidneys are not working properly, the kidneys release a lot more albumin into the urine. This is called albuminuria. That’s why blood albumin levels drop in kidney disease [10, 11].
5) Protein-Losing Enteropathy
Protein-losing enteropathy is a condition in which a lot of protein, including albumin, is being lost in the gut. This can happen in conditions such as celiac and Crohn’s disease, but also in some non-gut related disorders, such as Lupus [12, 10, 11, 13].
6) Heart Failure
Low albumin is common in people with heart failure. It results as a combination of various factors including inflammation, blood dilution, impaired liver function, and protein-losing enteropathy [10].
7) Severe Burns
Severe burns damage blood vessels near the surface of the skin. Blood fluid oozes through these wounds and albumin is lost with it, resulting in lowered albumin levels [10, 14].
Albumin levels are used to determine how severe burns are because the more extensive the burns are, the lower albumin levels fall [15].
8) Pregnancy
Anything that increases the fluid volume inside blood vessels, including pregnancy or receiving a large number of fluids intravenously, can also decrease blood albumin levels [16].
9) Some Genetic Disorders
Some mutations and variants of the albumin gene (ALB) also result in low albumin levels [17].
Congenital analbuminemia is a rare, recessive genetic condition that results in very low albumin levels. Most individuals with this condition are relatively healthy, but they may develop swelling, high cholesterol, osteoporosis, or respiratory tract infections [18].
Increasing Albumin
The most important thing is to work with your doctor to find out what’s causing your low albumin and to treat any underlying conditions. Low albumin levels are usually a symptom rather than a cause of illness, so treatment must, therefore, target the underlying cause. If albumin levels are below the normal range, a doctor may request further testing to check kidney and liver function.
Discuss the lifestyle changes listed below with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!
Make sure your diet is healthy and well balanced. It’s important that you are getting enough protein. Animal protein can increase albumin production, while vegetable protein (such as soy protein) can decrease the loss of albumin through urine. Choose lean, high-quality proteins whenever possible, including organic and hormone-free fish, and turkey [13, 19, 20].
Lose weight if you are overweight. Obesity is associated with chronic inflammation, which can lower albumin [21].
Get your recommended 6-8h of sleep each night. Extremes in sleep duration (<5h and >9h) have been associated with increased loss of albumin through urine [22].
Exercise regularly. Exercise stimulates albumin production [23, 24, 25].
You can also indirectly increase albumin by reducing chronic inflammation, as measured by the inflammatory markers c-reactive protein and interleukin-6.
High Levels
A high albumin level is anything that falls above the normal range as defined by the laboratory performing the test, usually more than 5.6 g/dL or 56 g/L. The condition of having high albumin is called hyperalbuminemia.
However, a result that’s higher than normal, doesn’t necessarily mean that you have a health condition needing treatment. Your doctor will interpret your albumin result, taking into account your medical history, symptoms, and other test results.
Causes of High Levels
Severe or chronic dehydration is a common cause of high albumin levels in blood tests because the total fluid volume of blood is decreased in dehydration while the amount of albumin stays the same. Dehydration can occur due to conditions such as severe vomiting and diarrhea, for example [13, 26].
In addition, there are several studies that have found a link between insulin resistance and higher blood albumin levels [27, 28, 29].
High blood albumin levels are associated with insulin resistance, but on its own, a high albumin level doesn’t predict the development of type 2 diabetes. In fact, one study of 15,428 human subjects found that individuals whose blood albumin levels increased the most over the 5-year study period had the lowest risk of developing type 2 diabetes [27, 30].
Decreasing Albumin
Work with your doctor to find out what’s causing your high albumin and to treat any underlying conditions.
Make sure you are drinking plenty of fluids. In addition, limit your alcohol intake, as it can cause dehydration [31, 32].
Albumin/Globulin Ratio
The albumin/globulin ratio, or A/G, is part of the Total Protein blood test. It measures the amount of albumin in blood relative to all the other proteins, collectively called globulins. The globulin level is calculated by subtracting the albumin from total protein.
Normal Ratio
The exact normal range for albumin/globulin will depend on the reference range of the laboratory that performs the test, however, it’s usually between 1.1 and 2.5.
In cases where albumin levels test low because of more fluid circulating in blood vessels, the albumin/globulin ratio will still be normal because all proteins are diluted equally.
Read more about the albumin/globulin ratio here.
Albumin Urine Test
In a healthy body, albumin passes through the kidneys but isn’t transferred into the urine. Even in the earliest stages of kidney disease, the kidneys may allow albumin to pass into the urine where it can be measured with a urine test, called a microalbumin test or albumin/creatinine ratio.
The test can be done on a single sample, known as a spot collection, or on a series of urine samples collected over 24 hours, called a 24-hour urine test.
Chronic conditions like diabetes and high blood pressure can increase the risk of developing kidney disease, so people with these conditions are usually given a microalbumin test every year to check their kidney function [33].
Albumin/Creatinine Ratio
The concentration of albumin in the urine can vary depending on the volume of urine output (it may test higher with low urine volume, or lower with high volume). To correct for this, a waste product of muscle metabolism, called creatinine, is also measured.
Creatinine is passed into urine at a known, constant rate, so its concentrations in different volumes of urine are predictable. By controlling for urine volume in this way, the ratio of albumin to creatinine is a more accurate measure of how much albumin is in the urine.
Ranges for Albumin/Creatinine Ratio
An albumin-creatinine ratio of less than 30 mg/g is considered normal to mildly increased, and it usually indicates kidney function is healthy.
A result between 30 – 300 mg/g is considered moderately increased. If moderately increased results are found on repeated urine tests given over a period of 3 months, it may indicate early stages of kidney disease.
A result greater than 300 mg/g is considered severely increased, and may be an indicator of advanced kidney disease.
Albumin in Diseases and Disorders
Ascites
Ascites is a condition in which fluids accumulate between the membrane that lines the abdominal wall and the membrane that encompasses the internal organs (this space is called the peritoneal cavity). It usually occurs as a result of liver disease or cancer that has spread around the body [34].
Ascites has several possible causes, one of which is low albumin levels. Because there is less albumin in the blood to maintain the osmotic pressure inside the vessels, fluids diffuse out of vessels into the peritoneal cavity.
Heart Disease
In a study of 4.5k people (Framingham Offspring Study), lower albumin levels were associated with an increased risk of developing heart disease over the next 20+ years [35].
In another study of 2.9k people, lower baseline albumin levels were associated with a higher risk of having heart failure over the following 9 years [36].
Therapeutic Uses of Albumin
Albumin-containing solution is often used in clinical practice. It has been used to [37, 38, 39, 40, 41, 42, 43]:
- increase blood volume
- treat sepsis
- treat and prevent ascites
- help in the treatment of liver disease (especially in the later stages)
- reduce problems in blood circulation
- help in plasmapheresis (removal, treatment, and return or exchange of blood plasma or blood components from and to the blood circulation)
- reduce the risk of death in patients with infections
- treat bacterial infections that occur in the fluid that builds up between membranes in the abdominal cavity
- prevent kidney failure
- help in extensive skin burns
- help treat of malnutrition
- help in kernicterus (a form of brain damage caused by too much of a compound called bilirubin)
- help in graft versus host disease
