What is the normal reference range for serum albumin in adults?

Normal Serum Albumin Reference Range

The normal serum albumin reference range in adults is 3.5-5.0 g/dL by electrophoretic methods (the gold standard) or 3.8-5.1 g/dL by the bromcresol green (BCG) colorimetric method, which is the most commonly used laboratory assay. 1

Method-Specific Reference Ranges

The reference range for serum albumin varies significantly depending on the laboratory methodology used:

• Electrophoretic methods (gold standard): 3.5-5.0 g/dL 2, 1
• Bromcresol green (BCG) method: 3.8-5.1 g/dL 2, 1
• Bromcresol purple (BCP) method: Laboratory-specific ranges should be used, as this method underestimates albumin by approximately 0.71 g/dL compared to more accurate methods 2, 1

Always confirm which laboratory method is being used, as different assays have different reference ranges and clinical reliability. 1 The BCG method is the most widely automated and reproducible assay used in clinical laboratories, with a low coefficient of variation (5.9%) and minimal interference from lipemia, salicylates, or bilirubin. 2

Critical Methodological Considerations

BCG vs. BCP Methods

• BCG is strongly preferred over BCP when available because BCP has proven less reliable clinically and underestimates values by approximately 19% in dialysis patients 2, 1
• The BCG method overestimates albumin in the low range by approximately 0.61 g/dL on average and differs from electrophoretic methods by about 0.3 g/dL 2, 1
• If BCP must be used, place less clinical weight on the absolute values and rely more heavily on other markers of nutritional status 2, 1

Age and Sex Variations

Reference intervals should ideally be stratified by age and sex, as population studies demonstrate significant variation. 3 Mean serum albumin concentration increases to peak around age 20 years, then decreases with increasing age. 3 Values in females decrease more rapidly but become close to male values at age 60 years. 3

The variation between laboratories can be large and potentially clinically significant, so laboratories should determine their own reference intervals rather than accepting a single consensus reference interval. 3, 4

Clinical Significance of Values

• A decline in albumin by ≥0.3 g/dL to <4.0 g/dL indicates nutritional deterioration in chronic kidney disease patients, even in the absence of acute infection or inflammation 2, 1
• Albumin levels <4.0 g/dL are associated with increased short- and long-term mortality in hospitalized patients, even when considered within the "normal" range 5
• The highest albumin level possible should be the goal for each patient, particularly in peritoneal dialysis populations 2

Common Pitfalls to Avoid

• Do not assume all laboratories use the same method or reference range – always verify the specific assay and its corresponding normal values 2, 1
• Do not overlook that albumin is an acute phase reactant – levels decrease during inflammation and catabolic illness independent of nutritional status 2
• Do not ignore pre-analytical factors such as prolonged tourniquet application during blood draw, which can cause hemoconcentration and falsely elevated values 1
• Do not use a single consensus reference interval across all populations given the significant age, sex, and methodological variations documented 3, 4