Albumin Levels: Normal Range & Clinical Meaning

What Is Albumin?

Albumin is the most abundant protein in human blood plasma, accounting for approximately 50–60% of total serum protein. It is synthesized exclusively by the liver at a rate of approximately 10–15 g/day and has a serum half-life of about 20 days. Normal serum albumin concentration ranges from 3.4 to 5.4 g/dL (34–54 g/L).

Albumin serves several critical physiological functions: it maintains oncotic pressure (the force that keeps fluid within blood vessels), transports a wide variety of substances (bilirubin, fatty acids, hormones, drugs, calcium, and medications including warfarin, phenytoin, and benzodiazepines), acts as an antioxidant and buffer, and modulates inflammation. About 60% of total body albumin is in the extravascular space.

Serum albumin is one of the most commonly measured laboratory values and is a powerful prognostic marker. Low albumin independently predicts poor surgical outcomes, increased length of hospital stay, higher complication rates, and mortality across nearly all clinical settings — from elective surgery to critical illness to chronic disease. However, interpreting albumin requires understanding that it is primarily a marker of disease severity and inflammation rather than nutritional status.

Normal Albumin Levels & Severity Classification

Note: Reference ranges may vary slightly between laboratories. SI conversion: albumin g/dL × 10 = g/L. Albumin has a half-life of approximately 20 days — changes in albumin reflect processes occurring over weeks, not hours.

What Does a High Albumin Level Mean?

Elevated serum albumin (>5.4 g/dL) is uncommon and essentially always reflects hemoconcentration from dehydration rather than true albumin overproduction. The liver does not upregulate albumin synthesis to supranormal levels.

Causes of High Albumin

• Dehydration (hemoconcentration) — the predominant and nearly exclusive cause. Reduced plasma water volume concentrates all serum proteins, including albumin
• Prolonged tourniquet application — a specimen collection artifact that can falsely elevate albumin and other proteins
• Upright posture — albumin is ~0.3 g/dL higher in ambulatory samples compared to supine samples due to fluid redistribution

Clinical Significance

An elevated albumin is primarily a signal to assess hydration status. It does not indicate a disease of albumin excess. If total protein and albumin are both elevated, dehydration is the most likely explanation. Treat the underlying cause — typically fluid resuscitation.

What Does a Low Albumin Level Mean?

Hypoalbuminemia (<3.4 g/dL) is extremely common in hospitalized patients and is one of the strongest non-specific prognostic markers in medicine. Understanding the mechanism helps guide workup.

Common Causes of Low Albumin

• Liver disease (decreased synthesis) — cirrhosis is the classic cause. The liver must lose ~75% of its synthetic capacity before albumin falls significantly. Albumin is a component of the Child-Pugh and MELD scores for liver disease staging
• Nephrotic syndrome (urinary loss) — glomerular damage allows massive albuminuria (>3.5 g/day). Severe hypoalbuminemia with edema, hyperlipidemia, and lipiduria is the hallmark presentation
• Inflammation and sepsis (negative acute-phase response) — pro-inflammatory cytokines (IL-6, TNF-α) suppress hepatic albumin synthesis and increase capillary permeability, redistributing albumin to the extravascular space. This is the most common cause of hypoalbuminemia in hospitalized patients
• Malnutrition — prolonged protein-calorie malnutrition (kwashiorkor, anorexia nervosa) reduces substrate for albumin synthesis. However, albumin's long half-life makes it a late and insensitive marker of nutritional depletion
• Burns — direct protein loss through damaged capillaries and skin; severe burns can cause precipitous albumin decline
• Protein-losing enteropathy — gastrointestinal protein loss in conditions such as inflammatory bowel disease, celiac disease, lymphangiectasia, and Ménétrier disease
• Heart failure — hemodilution, hepatic congestion impairing synthesis, and inflammatory activation all contribute
• Critical illness — capillary leak syndrome in sepsis and ARDS redistributes albumin to the interstitial space; levels can fall dramatically within 24–48 hours of ICU admission

Symptoms and Consequences of Low Albumin

• Edema — peripheral pitting edema, periorbital edema, ascites, and pleural effusions from reduced oncotic pressure
• Impaired wound healing — albumin is needed for tissue repair; surgical patients with albumin <3.0 g/dL have significantly higher complication rates
• Altered drug pharmacokinetics — many drugs are highly albumin-bound (warfarin, phenytoin, diazepam); low albumin increases the free (active) drug fraction, raising toxicity risk
• Increased infection risk — albumin has immunomodulatory and antioxidant functions
• Falsely low total calcium — calcium is partially bound to albumin; low albumin causes artificially low total calcium without affecting ionized calcium. Use corrected calcium or measure ionized calcium

Related Tests & Calculators

Albumin influences the interpretation of several other laboratory values and clinical scores:

• Corrected Calcium Calculator — adjusts total calcium for albumin level; essential when albumin is low to avoid missing true hypercalcemia or diagnosing false hypocalcemia
• Albumin-Corrected Anion Gap — adjusts the anion gap for low albumin, which unmasks hidden anion gap metabolic acidosis
• MELD Score Calculator — Model for End-Stage Liver Disease; uses bilirubin, INR, and creatinine (albumin is not in MELD but correlates with severity)
• Child-Pugh Score — classifies cirrhosis severity using albumin, bilirubin, INR, ascites, and encephalopathy
• FENa Calculator — fractional excretion of sodium; relevant in the workup of nephrotic syndrome with AKI

References

1. Tietz NW, ed. Tietz Clinical Guide to Laboratory Tests. 4th ed. WB Saunders; 2006.
2. Don BR, Kaysen GA. Serum albumin: relationship to inflammation and nutrition. Semin Dial. 2004;17(6):432–437.
3. Goldwasser P, Feldman J. Association of serum albumin and mortality risk. J Clin Epidemiol. 1997;50(6):693–703.
4. Finfer S, Bellomo R, Boyce N, et al. A comparison of albumin and saline for fluid resuscitation in the intensive care unit (SAFE Study). N Engl J Med. 2004;350(22):2247–2256.
5. White JV, Guenter P, Jensen G, et al. Consensus statement: Academy of Nutrition and Dietetics and American Society for Parenteral and Enteral Nutrition: characteristics recommended for the identification and documentation of adult malnutrition. JPEN J Parenter Enteral Nutr. 2012;36(3):275–283.