Sign in →

Test ID ALP Alkaline Phosphatase, Serum

Reporting Name

Alkaline Phosphatase, S

Useful For

Diagnosing and monitoring treatment of liver, bone, intestinal, and parathyroid diseases

Specimen Type


Necessary Information

Patient's age and sex are required.

Specimen Required

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Frozen (preferred) 60 days
  Ambient  7 days
  Refrigerated  7 days

Reference Values


4 years: 149-369 U/L

5 years: 179-416 U/L

6 years: 179-417 U/L

7 years: 172-405 U/L

8 years: 169-401 U/L

9 years: 175-411 U/L

10 years: 191-435 U/L

11 years: 185-507 U/L

12 years: 185-562 U/L

13 years: 182-587 U/L

14 years: 166-571 U/L

15 years: 138-511 U/L

16 years: 102-417 U/L

17 years: 69-311 U/L

18 years: 52-222 U/L

≥19 years: 45-115 U/L


4 years: 169-372 U/L

5 years: 162-355 U/L

6 years: 169-370 U/L

7 years: 183-402 U/L

8 years: 199-440 U/L

9 years: 212-468 U/L

10 years: 215-476 U/L

11 years: 178-526 U/L

12 years: 133-485 U/L

13 years: 120-449 U/L

14 years: 153-362 U/L

15 years: 75-274 U/L

16 years: 61-264 U/L

17-23 years: 52-144 U/L

24-45 years: 37-98 U/L

46-50 years: 39-100 U/L

51-55 years: 41-108 U/L

56-60 years: 46-118 U/L

61-65 years: 50-130 U/L

≥66 years: 55-142 U/L

Reference values have not been established for patients that are <4 years of age.

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
ALP Alkaline Phosphatase, S 6768-6


Result ID Test Result Name Result LOINC Value
ALP Alkaline Phosphatase, S 6768-6

Clinical Information

Alkaline phosphatase (ALP) is present in a number of tissues including liver, bone, intestine, and placenta. Serum ALP is of interest in the diagnosis of 2 main groups of conditions-hepatobiliary disease and bone disease associated with increased osteoblastic activity.


A rise in ALP activity occurs with all forms of cholestasis, particularly with obstructive jaundice. The response of the liver to any form of biliary tree obstruction is to synthesize more ALP. The main site of new enzyme synthesis is the hepatocytes adjacent to the biliary canaliculi.


ALP also is elevated in disorders of the skeletal system that involve osteoblast hyperactivity and bone remodeling, such as Paget disease, hyperparathyroidism, rickets and osteomalacia, fractures, and malignant tumors. A considerable rise in alkaline phosphatase activity caused by increased osteoblast activity following accelerated bone growth is sometimes seen in children and juveniles.


The elevation in alkaline phosphatase (ALP) tends to be more marked (more than 3 fold) in extrahepatic biliary obstruction (eg, by stone or by cancer of the head of the pancreas) than in intrahepatic obstruction, and is greater the more complete the obstruction. Serum enzyme activities may reach 10 to 12 times the upper limit of normal, returning to normal on surgical removal of the obstruction.


The ALP response to cholestatic liver disease is similar to the response of gamma-glutamyltransferase (GGT), but more blunted. If both GGT and ALP are elevated, a liver source of the ALP is likely. Among bone diseases, the highest level of ALP activity is encountered in Paget disease as a result of the action of the osteoblastic cells as they try to rebuild bone that is being resorbed by the uncontrolled activity of osteoclasts. Values from 10 to 25 times the upper limit of the reference interval are not unusual. Only moderate rises are observed in osteomalacia, while levels are generally normal in osteoporosis. In rickets, levels 2 to 4 times normal may be observed. Primary and secondary hyperparathyroidism are associated with slight to moderate elevations of ALP; the existence and degree of elevation reflects the presence and extent of skeletal involvement. Very high enzyme levels are present in patients with osteogenic bone cancer. A considerable rise in ALP is seen in children following accelerated bone growth.


In addition, an increase of 2 to 3 times normal may be observed in women in the third trimester of pregnancy, although the interval is very wide and levels may not exceed the upper limit of the reference interval in some cases. The additional enzyme is of placental origin.

Clinical Reference

Tietz NW: Textbook of Clinical Chemistry. Third edition, Edited by Burtis and Ashwood. Philadelphia, PA, WB Saunders Company, Philadelphia, 1999.

Analytic Time

Same day/1 day

Method Name

Photometric, p-Nitrophenol Phosphate


If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Test Request Form (T728) with the specimen (