Serum albumin

What it reflects

Albumin is made in the liver and maintains the oncotic pressure that keeps fluid inside blood vessels. It also transports hormones, fatty acids, calcium and many drugs, which is why albumin appears in the free testosterone calculation.

Its level is set by three things at once: liver synthetic capacity, inflammatory state, and losses through the kidney or gut. Nutrition matters, but far less than most people assume.

Why it predicts outcomes

Low albumin is associated with higher mortality across an enormous range of populations, including apparently healthy adults, and the association survives adjustment for obvious confounders. It is one of the nine inputs in the PhenoAge biological age algorithm for exactly that reason.

The likely explanation is that albumin integrates chronic inflammation and liver function into a single number. Inflammatory cytokines suppress albumin synthesis, so a persistently low-normal albumin often means low grade inflammation rather than a dietary problem.

Reading a low result

Meaningful causes are liver disease, protein losing kidney disease, inflammatory bowel disease, heart failure and any significant inflammatory or infectious process. Overhydration lowers it dilutionally, and a tourniquet held too long or prolonged standing can shift it slightly.

Eating more protein does not fix a low albumin caused by inflammation. Finding the inflammation does.

References

1. Levine ME, et al. An epigenetic biomarker of aging for lifespan and healthspan. Aging (Albany NY). 2018.
2. Goldwasser P, Feldman J. Association of serum albumin and mortality risk. J Clin Epidemiol. 1997.
3. Don BR, Kaysen G. Serum albumin: relationship to inflammation and nutrition. Semin Dial. 2004.