Albumin - Kresser Institute Membership Site

Marker Name: Albumin

REFERENCE RANGES FOR ALBUMIN:

Laboratory reference range: 3.5–5.5 g/dL

Functional reference range: 4–5 g/dL

DESCRIPTION:

Albumin is the most abundant protein found in the blood. It comprises approximately 60 percent of the proteins in plasma.¹ Albumin contributes to the osmotic pressure within blood vessels, which is important for fluid balance in peripheral tissues.² The plasma protein acts as a carrier for various molecules including calcium, unconjugated bilirubin, thyroid hormones, long-chain fatty acids, toxic heavy metal ions, and many drugs.^2,3

Albumin is synthesized by the liver.² Biosynthesis of albumin requires sufficient amounts of essential amino acids (i.e., histidine, leucine, isoleucine, lysine, phenylalanine, methionine, threonine, tryptophan, and valine).⁴ In healthy individuals, the rate of albumin synthesis roughly equals the rate at which protein is utilized, catabolized, or excreted.¹ Compared to other proteins, albumin has a relatively long half-life and remains reasonably constant.² The intravascular half-life of albumin is 16 hours, but the half-life in tissues is 19 days.^5-7

Albumin levels are relatively constant, even during early phases of nutritional deficiency or liver disease. Therefore, the serum marker is not a sensitive indicator of these conditions. Prealbumin proteins such as transthyretin, retinol-binding protein, and coagulation factors have shorter half-lives and are faster to herald the onset of nutritional or biosynthetic abnormality.² Low serum albumin levels strongly correlate with morbidity and mortality; every 10 g/L decrease in serum albumin is associated with a 137 percent increase in mortality risk and an 89 percent increase in morbidity risk.⁵

Hyperalbuminemia, or the abnormal elevation of albumin in the blood, generally reflects dehydration and hemoconcentration.⁸ Mild elevations in albumin may be caused by high-protein diets, though the clinical consequence of this is negligible.⁹ Hepatocellular carcinoma could theoretically stimulate the synthesis of albumin resulting in elevated levels in the serum, but this is exceedingly rare.¹⁰

It is much more common for albumin levels to be abnormally low (i.e., hypoalbuminemia). Hypoalbuminemia can be caused by dilution from relative increases in intravascular fluids. Low serum albumin levels usually indicate impaired biosynthesis in the liver, insufficient protein intake, increased tissue catabolism of protein, impaired protein absorption, or protein loss from renal excretion.³ Albumin levels may be abnormally low in patients with acute inflammation, shock, or protein-wasting enteropathy.⁸ An extremely rare autosomal recessive condition called analbuminemia results in a complete lack of circulating albumin.¹¹ Curiously, this condition generally results in nothing more serious than edema.^2,11

Albumin is a standard component of the liver panel, which includes alanine aminotransferase (ALT), acetate aminotransferase (AST), alkaline phosphatase, bilirubin, and total protein.¹²

PATHOLOGICAL/CONVENTIONAL RANGE INDICATIONS:

High in:^8-10

Hemoconcentration
- Inadequate water intake
- Excessive diuresis
High-protein diet with protein supplementation (rare)
Hepatocellular carcinoma (rare)

Low in:^2,13-16

Hemodilution
- Intravenous fluids
- Advanced congestive heart failure
- Polydipsia
Protein malnutrition
Protein malabsorption
Liver failure
Advanced liver disease
Renal failure
Nephrotic syndrome
Inflammation
Protein-losing enteropathy
- Primary gastrointestinal mucosal diseases (e.g., ulcerative colitis)
- Increased interstitial pressure or lymphatic obstruction (e.g., sarcoidosis)
- Non-erosive upper gastrointestinal diseases (e.g., celiac sprue)
Analbuminemia

FUNCTIONAL RANGE INDICATIONS:

High in:

Dehydration (hematocrit, hemoglobin, and red blood cells will also often be elevated in functional range)

Low in:

Impaired liver function
Inflammation

References: