ALB

Albumin

Liver Function

What is Albumin?

Albumin is the most abundant protein in human blood plasma, accounting for about 55–60% of total serum protein. It is synthesized exclusively by the liver at a rate of approximately 10–15 grams per day, with a half-life of about 20 days. Albumin serves several critical functions: it maintains oncotic pressure (keeping fluid in blood vessels and preventing edema), transports hormones, fatty acids, drugs, and bilirubin, and acts as an antioxidant and buffer for acid-base balance.

Serum albumin is measured as part of the comprehensive metabolic panel and liver function tests. Because albumin is produced by the liver and has a relatively long half-life, low albumin (hypoalbuminemia) is a marker of chronic liver disease, malnutrition, or protein-losing conditions. Albumin is not a good indicator of acute liver damage because its long half-life means levels don't drop quickly after acute injury. However, in chronic liver disease, falling albumin indicates worsening synthetic function and is a component of the Child-Pugh and MELD scores used to assess liver disease severity and transplant eligibility.

Why It Matters

Albumin is one of the best markers of the liver's synthetic capacity and overall nutritional status. Low albumin causes edema (fluid accumulation in tissues), increases the risk of infection, impairs wound healing, and is associated with worse outcomes in hospitalized patients. It is a key prognostic indicator in liver cirrhosis, nephrotic syndrome, and critical illness. Albumin levels also affect the interpretation of other tests—notably calcium, which must be corrected for albumin when albumin is low.

Normal Reference Ranges

GroupRangeUnit
Adults3.5–5.5g/dL
Children3.8–5.4g/dL
Elderly (>60)3.4–4.8g/dL

Reference ranges may vary by laboratory. Always compare results to the ranges provided by your testing facility.

What High ALB Levels Mean

Common Causes

  • Dehydration (most common cause of apparently high albumin)
  • High-protein diet (minimal effect)
  • Rarely clinically significant

Possible Symptoms

  • Symptoms of dehydration: thirst, dark urine, dizziness

What to do: High albumin is almost always due to dehydration rather than true excess. Rehydration will normalize levels. If albumin is genuinely elevated above 5.5 g/dL without dehydration, it rarely has clinical significance.

What Low ALB Levels Mean

Common Causes

  • Liver cirrhosis or chronic liver disease
  • Nephrotic syndrome (loss of albumin in urine)
  • Malnutrition or malabsorption
  • Chronic inflammation (albumin is a negative acute-phase reactant)
  • Burns (loss of protein through damaged skin)
  • Protein-losing enteropathy
  • Heart failure
  • Sepsis and critical illness

Possible Symptoms

  • Edema (swelling in legs, ankles, abdomen)
  • Ascites (fluid in the abdomen)
  • Fatigue
  • Muscle wasting
  • Slow wound healing
  • Increased susceptibility to infections

What to do: Low albumin requires identification of the underlying cause. Check liver function tests, urinalysis for proteinuria (nephrotic syndrome), and inflammatory markers (CRP). Assess nutritional status and dietary protein intake. Treatment addresses the cause: nutrition optimization, diuretics for edema, managing liver disease, immunosuppressive therapy for nephrotic syndrome. IV albumin infusions are used in specific clinical situations (large-volume paracentesis, spontaneous bacterial peritonitis, hepatorenal syndrome) but not routinely for all hypoalbuminemia.

When Is ALB Testing Recommended?

  • As part of a comprehensive metabolic panel
  • When evaluating liver function and disease severity
  • When edema or ascites is present
  • To assess nutritional status
  • When monitoring nephrotic syndrome
  • In critically ill or hospitalized patients

Frequently Asked Questions

Albumin is the primary protein responsible for maintaining oncotic pressure—the force that keeps fluid inside blood vessels. When albumin levels drop below about 2.5 g/dL, oncotic pressure decreases and fluid leaks out of blood vessels into surrounding tissues, causing edema. This is most noticeable in the legs and ankles (peripheral edema) due to gravity, and in the abdomen (ascites) in liver disease. The relationship is sometimes described by Starling's forces: the balance between hydrostatic pressure (pushing fluid out) and oncotic pressure (pulling fluid in) determines fluid distribution.
Albumin has traditionally been used as a nutritional marker, but it has limitations. Because albumin is a negative acute-phase reactant, its levels drop during inflammation, infection, and stress—regardless of nutritional status. A critically ill patient may have low albumin despite adequate nutrition simply due to the inflammatory response. Prealbumin (transthyretin), with its shorter half-life of 2 days, responds more quickly to nutritional changes. The best approach uses multiple markers: albumin, prealbumin, body weight, dietary assessment, and clinical examination together.
About 45% of blood calcium is bound to albumin. When albumin is low, less calcium is bound, so the total calcium measurement appears low even though the biologically active ionized calcium may be normal—this is called pseudohypocalcemia. The correction formula adds 0.8 mg/dL to total calcium for every 1 g/dL that albumin is below 4.0 g/dL. For example, if albumin is 2.0 g/dL and calcium is 7.5 mg/dL, the corrected calcium is 7.5 + (0.8 × 2.0) = 9.1 mg/dL. Alternatively, ionized calcium can be measured directly for the most accurate assessment.

Related Biomarkers

ALTAlanine AminotransferaseASTAspartate AminotransferaseTBILBilirubinCaCalciumCrCreatinine

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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation of your specific test results.

Disclaimer: SymptomGPT is not a medical diagnosis tool and does not provide medical advice. Always consult a qualified healthcare professional. If you are experiencing a medical emergency, call 911 immediately.