Chemical Pathology


  • The enzyme is found in liver and bone but also in placental and intestinal tissue.
  • Total phosphatase enzyme activity at alkaline pH is assessed.

Sample requirements

For adults, blood taken into a 5mL gold top gel tube (or rust top for the Acute Unit)

5ml gold tube

For children, blood taken into a 3.5mL rust top tube

3.5ml rust top tube

For neonates, blood taken into a 0.8mL minicollect ithium heparin tube.

Sample tube: pale green cap


Send at ambient temperature to the laboratory. If unavoidable, samples can be stored refrigerated overnight.

Required information

Relevant clinical details state including known or possible diagnoses; if a liver or bone pathology is suspected; if the patient is pregnant. List relevant current medications e.g.anticonvulsant.

Turnaround times

The assays are run throughout the day and night. The in-lab turnaround time is normally less than 24 hours. The test can be ordered as an urgent request.

Reference ranges

Age Reference range (U/L)
< 1 month 90 - 260
1 month - 3 years 90 - 180
3 - 10 years 130 - 260
10 - 14 years 130 - 340
14 - 18 years 30 - 180
> 18 years 30 - 130

Further information

  • Gamma GT (γGT) may be a useful additional test when alkaline phosphatase is raised. If γGT is also raised then some, if not all, of the increase in alkaline phosphatase is likely to be of liver origin.
  • Alkaline phosphatase is produced by the placenta. High levels occur in pregnancy and the normal reference ranges do not then apply. No reference ranges exist for pregnancy - levels will be dependent on size of the placenta.
  • Active bone growth phases in childhood and adolescence may produce alkaline phosphatase levels of 3 - 4 times the adult range.
  • Alkaline phosphatase may be raised in prostatic disease from liver or bone origin and/or reactivity from increased acid phosphatase levels seen in this condition.
  • If γGT is within the reference range and the source of the raised alkaline phosphatase is still clinically unclear (other liver enzyme levels normal) then very occasionally follow up with alkaline phosphatase isoenzyme analysis may be useful. This involves sending a serum sample to North Bristol NHS Trust, with results normally available within 2 weeks. Please note that all isoenzyme requests have to be agreed with the duty biochemist.

To learn more about alkaline phosphatase, visit Lab Tests Online

Page last updated: 20/04/2021