Alkaline Phosphatase

An alkaline phosphatase level test (ALP test) measures the amount of alkaline phosphatase enzyme in your bloodstream. The test requires a simple blood draw and is often a routine part of other blood tests.

Also Known asALP, ALK, Alkp, ALK PHOS, Isoenzyme Test, ALP Fractionation Test
Test PurposeFor measures the amount of alkaline phosphatase enzyme in your bloodstream
Test PreparationsNo Need any Preparations, But Overnight Fasting Is Preferred.
Test ComponentsAlkaline Phosphatase
Specimen2 ML (0.5 ML Min.) Serum From 1 SST. Hemolysed Specimens Are Not Acceptable. Ship Refrigerated Or Frozen. Overnight Fasting Is Preferred.
Stability Room4 Hours
Stability Refrigerated72 Hours
Stability Frozen4 Weeks
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Alkaline Phosphatase

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Alkaline Phosphatase (ALP) is an enzyme found in:

  • Bone
  • Liver
  • Placenta
  • Kidney
  • Intestines

Why Get Tested :

When to Get Tested :

As part of a routine liver panel or when you have symptoms of a liver or bone disorder

When ALP Test Orderd :

An ALP test may be ordered as part of routine laboratory testing, often with a group of other tests called a liver panel. It is also usually ordered along with several other tests when a person has symptoms of a liver or bone disorder.

Signs and symptoms of liver involvement may include:

  • Weakness, fatigue
  • Loss of appetite
  • Nausea, vomiting
  • Abdominal swelling and/or pain
  • Jaundice
  • Dark urine, light-colored stool
  • Itching (pruritus)

Some examples of the signs and symptoms suggesting a bone disorder include:

  • Bone and/or joint pain
  • Increased frequency of fractures
  • Deformed bones

Sample Required :

  1. It is done on the Serum of the patient.
  2. A fasting sample is a better choice.
  3. This test can be done on the random sample as well.
    • How to get good serum: Take 3 to 5 ml of blood in the disposable syringe or in vacutainer. Keep the syringe for 15 to 30 minutes at 37 C and then centrifuge for 2 to 4 minutes to get the clear serum.
  4. Keep the sample refrigerated as soon as you separate the serum.
  5. Serum at 0 to 4 °C is stable for 2 to 3 days and at -25 °C is for one month.
  6. Perform the test as soon as possible because ALP activity increases 3 to 10% on standing at 25° C or 4 ° C for several hours.

Precautions for Sample :

  1. Storage At room temperature increases the ALP activity.
  2. Avoid EDTA and oxalate anticoagulant which decreases Alkaline phosphatase activity.
  3. If serum left at room temperature:
    • Then there is a 1% increase in 6 hours.
    • 3 to 6% in 1 to 4 days.
    • Even may see an increase if refrigerated the serum which is 2%/day.
  4. Recent intake of food may increase the value.
    1. Values may be 25% higher after taking the high-fat meal.
  5. Drugs like allopurinol, antibiotics, colchicine, indomethacin, fluorides, isoniazid (INH), methotrexate, nicotinic acid, methyldopa, phenothiazine, and probenecid can increase the alkaline phosphatase level.
  6. Drugs like arsenal, cyanides, nitrofurantoin, and zinc salts may decrease the alkaline phosphatase level.
  7. Hemolysis may cause a slight increase in the ALP. ALP is 6 times more in the RBC than the serum.

Normal values :

Source 1

Adult Male25 to 100 U/L
Adult Female25 to 100 U/L
Children/adult<2 years  = 85 to 235 U/L
2 to 8 years  = 65 to 210 U/L
9 to 15 years =  60 to 300 U/L
16 to 21 years = 30 to 200 U/L

Source 2


  • 1 to 12 years = <350 U/L
  • 12 to 14 years = <500 U/L
  • >20 years = 25 to 100 U/L


  • 1 to 12 years = <350 U/L
  • >15 years = 25 to 100 U/L

ALP Decreased level seen in:

DiseaseALP increasedExplanation
Paget’s disease10 to 25 timesOsteoblastic activity increase the ALP 
OsteomalaciaModerate increaseLevel lowers with treatment
Rickets2 to 4 timesLevel lowers with treatment
OsteoporosisNormal level 
Healing fracture mild raised level 
Fanconi’s syndromeMild to moderate increase 
Primary and secondary hyperparathyroidismmild to moderate increase 
Osteogenic sarcomaVery high level 
Pregnancy third trimester2 to 3-time increaseThis is the placental origin
Children 1.5 to 2.5-times increaseGrowing age 
Metastatic tumor-like Ca prostateraised level

Other causes for raised level:

  1. It is also raised in old age and pregnancy.
  2. Hodgkin’s disease.
  3. Sarcoidosis.
  4. Amyloidosis.
  5. Pulmonary and myocardial infarction.
  6. Hyperthyroidism (with a raised level of calcium).
  7. Chronic renal failure.
  8. Ulcerative colitis.
  9. ALP is increased during the last trimester of pregnancy and falls to normal within 3 to 6 months (postpartum).
  10. Hyperparathyroidism.

ALP Decreased level seen in:

  1. Malnutrition.
  2. Hypothyroidism ( Cretinism ).
  3. Milk-alkali syndrome.
  4. Celiac sprue.
  5. Scurvy ( vit.C deficiency ).
  6. Gross anemia.
  7. Deposition of radioactive material in the bone.
  8. In hypophosphatemia.
  9. Pernicious anemia.
  10. Nutritional deficiency of zinc or magnesium.

Interpretation of the Alkaline Phosphatase:

  1.  If there is no jaundice and there is raised ALP indicates liver malignancy, drug-induced injury, rarely sarcoidosis and cyst.
  2. ALP presence in the urine indicates renal diseases like renal cell carcinoma, nephrosis, nephritis, SLE, and infarction. 
  3. ALP raised in the third trimester of pregnancy indicates placental origin. 
  4. In osteoclastic activity ALP is normal.
  5. In the osteoblastic activity, ALP is raised.

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