Albumin is a blood protein that delivers vitamins, minerals, and medications all around your body. It also provides an important clue to your overall health and can even predict your chances of dying. Read on to learn more about this important protein and how you can use it to your advantage.
- Introduction to Albumin
- Albumin Blood Test
- Albumin/Globulin Ratio
- Albumin Urine Tests
- Albumin in Diseases and Disorders
- Therapeutic Uses of Albumin
Introduction to Albumin
Albumins actually comprise a family of proteins that share a similar globe-like structure and are found in animals. The albumin found in human blood, human serum albumin, is the primary focus of this article.
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 [R].
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.
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 to 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 Blood Test
An albumin blood test measures the amount of albumin in blood. Low albumin is common in many health problems, so albumin levels are often checked in conjunction with other tests to diagnose diseases, determine if other tests are needed, or to check if treatments of 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 Albumin Levels
The exact range for normal albumin levels depends on the specific laboratory that performs the blood test, however, it is usually around 3.4 to 5.4 g/dL or 34 to 54 g/L.
Normal-high albumin levels are an indicator of general good health. Albumin levels of 4.5 gm/dL or higher are associated with a decreased risk of death from all causes, including congestive heart failure, and cancer patients with higher pre-treatment albumin levels are more likely to survive [R, R].
Low Albumin Levels
A low albumin level is anything that falls below the normal range as defined by the laboratory performing the test, usually less than 3.4 g/dL or 34 g/L. The condition of having low albumin is called hypoalbuminemia.
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 [R].
Albumin levels can be used as a measure of how severe an illness is, with lower levels associated with worse outcomes. A meta-analysis found that as albumin level decreases, the odds of dying increase [R].
Causes of Low Albumin Levels
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 [R, R].
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 malnutrition seen in famines that is extremely rare in the developed world [R, R].
Numerous studies show that when healthy adults consume more dietary protein, it increases albumin production in the short term. However, these studies do not look directly at blood albumin levels and don’t consider changes in the rate at which albumin is eliminated [R].
Because albumin is produced in the liver, liver diseases that interrupt albumin production can cause low levels.
Low albumin levels are seen in the following diseases, disorders, and health conditions:
- Extensive burns [R]
- Cancer [R]
- Carcinoid syndrome [R]
- Congestive heart failure [R]
- Diabetes [R]
- Hypothyroidism [R]
- Infection [R]
- Inflammation, both chronic and acute [R]
- Kidney diseases [R]
- Liver disorders [R]
- Nephrotic syndrome [R]
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.
Some mutations and variants of the albumin gene (ALB) also result in low albumin levels [R].
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 [R].
Treatment for Low Albumin Levels
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.
Ways to Increase Albumin Levels
Inflammation is the most common underlying cause of low albumin levels, so in the absence of obvious illness, an anti-inflammatory diet may be the best way to improve albumin levels.
These supplements can help increase albumin:
- amino acids (especially branched-chain) [R, R, R, R, R]
- N-acetyl cysteine [R, R, R]
- Vitamin C and vitamin E [R, R]
- Vitamin D (if you are deficient) [R, R, R]
- fish oil/omega-3 fatty acids [R, R]
- probiotics [R, R]
- carotenoids [R, R]
- fiber [R, R]
- Thiamine/vitamin B1 [R]
- Folic acid [R, R]
- selenium [R]
- glutathione [R]
- curcumin [R]
- ginseng [R]
High Albumin Levels
A high albumin level is anything that falls above the normal range as defined by the laboratory performing the test, usually more than 53.4 g/dL or 54 g/L. The condition of having high albumin is called hyperalbuminemia.
Causes of High Albumin 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.
A case study of two patients suffering from abdominal pain and high albumin levels found that their albumin levels returned to normal and abdominal pains ceased once they stopped taking protein supplements and eating a high protein diet [R].
This study may suggest that a very high protein diet and/or taking large amounts of protein supplements can cause high albumin levels in some individuals. However, because this was an observation in two people and not a controlled study, it shouldn’t be given the same weight as more rigorous research that has established albumin levels are not affected by dietary protein intake except in rare circumstances [R].
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 Albumin/Globulin 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 0.8 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.
Low Albumin/Globulin Ratio
A low albumin/globulin ratio means that albumin levels are low, globulin levels are high, or both.
Globulin levels may be elevated due to inflammation, autoimmune diseases, and plasma cell cancer called multiple myeloma [R].
High Albumin/Globulin Ratio
Some leukemias and genetic conditions can result in not enough immune system proteins being made, which would cause a high albumin/globulin ratio.
Albumin Urine Tests
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 [R].
The concentration of albumin in 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 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 indicates the early stages of kidney disease.
A result greater than 300 mg/g is considered severely increased, and an indicator of advanced kidney disease.
Albumin in Diseases and Disorders
Albumin and 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 [R].
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.
Albumin and Burns
Albumin levels are used to determine how severe burns are because the more extensive the burns are, the lower albumin levels fall [R].
Severe burns result in damaged blood vessels near the surface of the skin. These wounds cause the formation of oozing fluids by the body, through which albumin is lost, resulting in lowered albumin levels [R].
Albumin and Cancer
The lower the albumin levels are before treatment for cancer, the worse the prognosis. According to a systematic review of 59 research studies, cancer patients who had higher albumin levels before the treatment were more likely to survive gastrointestinal cancers, lung cancer, cancers of the female reproductive organs, multiple cancers, and other cancers [R].
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 [R].
Albumin and Carcinoid Syndrome
Carcinoid tumors are a type of slow-growing, cancerous tumor that usually occurs in the small intestine, rectum, stomach, or appendix. A subset of these tumors can secrete hormones, particularly serotonin, which results in carcinoid syndrome. The symptoms can include diarrhea, difficulty breathing, flushed skin, and periods of rapid heartbeat, as well as low albumin levels [R].
Serotonin is made (in part) from the amino acid L-tryptophan, which is also necessary for the production of albumin. The excessive serotonin production in carcinoid syndrome depletes the body of L-tryptophan, which results in less albumin being made and thus, low albumin levels [R].
Albumin and Congestive Heart Failure
Albumin and Diabetes
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 [R, R].
Kidney disease is a common risk for diabetics, so they are given a urine test at least once a year to check for albumin in the urine. As kidney disease progresses, more and more albumin is allowed to pass from the blood into the urine, resulting in a high albumin/creatinine ratio.
Albumin and Kidney Disease (Nephrotic Syndrome)
The kidneys filter waste and extra fluid from the blood so they can be excreted in urine. Nephrotic syndrome is a disease in which the kidneys stop functioning correctly and allow albumin to pass into the urine. As a result, blood albumin levels decrease, and urine albumin levels (albumin/creatinine ratios) increase [R].
Albumin and Liver Disease
Cirrhosis of the liver is a complication of liver disease in which liver cells are damaged and replaced with scar tissue. Because albumin is produced by the liver, the damage to liver cells results in less albumin being produced and structural changes in the albumin, which prevent it from functioning normally [R, R].
Albumin is given intravenously to patients with liver disease to treat multiple conditions.
Therapeutic Uses of Albumin
- treat sepsis
- help in the treatment of liver disease (especially in the later stages)
- reduce problems in blood circulation
- reduce the risk of death in patients with infections
- increase blood volume
- treat and prevent ascites
- treat bacterial infections that occur in the fluid that builds up between membranes in the abdominal cavity
- prevent kidney failure
- extensive skin burns
Although it is also sometimes used in plasmapheresis and in the treatment of malnutrition, kernicterus (a form of brain damage caused by too much of a compound called bilirubin), and graft versus host disease, there is no evidence that it is effective for these conditions [R].
There isn’t adequate research to determine if giving albumin to patients with low albumin is beneficial for those with heart failure [R].
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