Albumin is the most abundant plasma protein, accounting for 55–60% of serum protein. It has a complex structure with 585 amino acids and 17 disulphide bridges, and plays a crucial role in maintaining oncotic pressure, transporting substances, and acting as a buffer. In critical illness, albumin distribution shifts between intravascular and extravascular compartments, and its synthesis and degradation are altered. Low serum albumin is associated with poor outcomes, but studies show no benefit of albumin therapy in critically ill patients. Albumin's role in critical illness is complex, with changes in capillary permeability and inflammatory responses contributing to its altered function. While albumin has potential therapeutic uses, evidence does not support its use for hypoalbuminaemia or hypovolaemia in critically ill patients. The use of albumin remains controversial, with conflicting data on its effectiveness. Future research is needed to clarify its role in critical illness.Albumin is the most abundant plasma protein, accounting for 55–60% of serum protein. It has a complex structure with 585 amino acids and 17 disulphide bridges, and plays a crucial role in maintaining oncotic pressure, transporting substances, and acting as a buffer. In critical illness, albumin distribution shifts between intravascular and extravascular compartments, and its synthesis and degradation are altered. Low serum albumin is associated with poor outcomes, but studies show no benefit of albumin therapy in critically ill patients. Albumin's role in critical illness is complex, with changes in capillary permeability and inflammatory responses contributing to its altered function. While albumin has potential therapeutic uses, evidence does not support its use for hypoalbuminaemia or hypovolaemia in critically ill patients. The use of albumin remains controversial, with conflicting data on its effectiveness. Future research is needed to clarify its role in critical illness.