Serum Acid Phosphatase

Serum acid phosphatase is an enzyme that hydrolyzes phosphate esters optimally in acidic conditions. It’s produced by the prostate, liver, bone, red blood cells and platelets. Elevated serum levels can indicate prostate disease (including cancer), bone disorders, liver damage or hemolysis. It was historically used to monitor prostate cancer; more specific tests are now preferred.

When acid phosphatase is high, it means an enzyme normally released from prostate, bone, liver, spleen and blood cells is elevated. Causes include prostate disease (prostatitis, benign enlargement, or prostate cancer), bone disorders or bone metastases, liver disease, certain blood disorders or recent tissue injury/hemolysis. The result is non‑specific—your doctor will order further tests (PSA, imaging, specialist review) to find the cause.

An acid phosphatase (ACP) test measures levels of the enzyme acid phosphatase in blood or other fluids. Elevated ACP—especially prostatic acid phosphatase—can indicate prostate disease, including prostate cancer and metastasis, though PSA largely replaced it for screening. Increased levels may also reflect bone or liver disorders. ACP testing of swabs or fluids can help detect semen in forensic cases.

Not exactly. Acid phosphatase — especially prostatic acid phosphatase (PAP) — was historically used as a marker for prostate cancer, particularly to assess advanced or metastatic disease. It is not specific for cancer and can be raised in benign bone, liver, or blood disorders. It’s largely been superseded by PSA, and acid phosphatase alone cannot diagnose cancer; clinical evaluation and imaging are needed.

Normal serum acid phosphatase varies by laboratory and assay. Typical adult reference ranges are about 0–5 U/L for total acid phosphatase (some labs report up to ~10 U/L). Prostatic acid phosphatase (PAP) is usually very low, often <1–2 U/L. Always compare results with the lab’s reference range and discuss abnormal values with your clinician.

Acid phosphatase in the liver is a lysosomal enzyme that hydrolyzes phosphate esters at acidic pH, supporting intracellular digestion and recycling of macromolecules. It dephosphorylates nucleotides, proteins and lipids within lysosomes, aiding biomolecule turnover, phosphate mobilization and metabolic regulation. Elevated serum levels may indicate hepatocellular or lysosomal injury, though its primary role is intracellular dephosphorylation and catabolism.