Phosphorus (PO4)

Clinical definition of the phosphorus test
A phosphorus blood test is done to assess phosphorus levels in the blood. Phosphorus is the most abundant mineral found in the body and obtained mostly from food, such as milk, grains, and protein-rich foods. Phosphorus in the body is found in bones and teeth, and is also present in cells and tissues throughout the body. Phosphorus helps:

  • To form healthy bones and teeth
  • Process energy in the body
  • Support muscle and nerve functioning
  • Reduce muscle pain after a hard work out
  • For the growth, maintenance, and repair of all tissues and cells, and for the production of the genetic building blocks, DNA and RNA
  • Filter out waste in the kidneys

Conditions such as diabetes, starvation, and alcoholism can cause levels of phosphorus in the body to fall. The body maintains phosphorus/phosphate levels in the blood by regulating how much it absorbs from the intestines and how much it excretes via the kidneys.

Why is the phosphorus test done?
Phosphorus test is done to evaluate the level of phosphorus in the blood and to aid in the diagnosis of conditions known to cause abnormally high or low levels.

What are the common signs/symptoms when the phosphorus test is done?

  • Loss of appetite
  • Anxiety
  • Bone pain
  • Fragile bones
  • Stiff joints
  • Fatigue
  • Irregular breathing
  • Irritability
  • Numbness
  • Weakness
  • Weight change
  • Decreased growth and poor bone and tooth development in children

What should I do before the phosphorus test?

Specimen type

Specimen collection procedure

Preparatory instructions before the test *

Serum (Blood Sample)

Venipuncture - Collection of blood from a vein, usually from the arm.

No Fasting Required.

No other special preparations required.

*Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my phosphorus test results?

Reference Range*


2.3 – 4.7 mg/dl


‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’

Diseases/conditions related to the phosphorus test

  • Hypercalcemia
  • Malnutrition
  • Alcoholism
  • Severe burns
  • Diabetic ketoacidosis (after treatment)
  • Hypothyroidism
  • Hypokalemia
  • Chronic antacid use 
  • Rickets and osteomalacia (due to Vitamin D deficiencies)
  • Kidney failure
  • Hypoparathyroidism
  • Hyperinsulinism
  • Hyperparathyroidism
  • Malnutrition
  • Rickets (childhood) or osteomalacia (adult)

Other tests related to the phosphorus test

  • Calcium
  • Electrolyte Panel
  • Vitamin D
  • Parathyroid Hormone (PTH)
  • Magnesium

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Phosphorus (Serum)