What is the Phosphorus Test?
There are two names for the phosphorus blood test – phosphorus or inorganic phosphate. The test reports the amount of phosphate found in blood. If calcium and/or phosphorus levels are abnormal, the phosphorus test is typically ordered with a series of blood tests to determine the cause. Other tests that may be ordered with the phosphorus test include measurements of calcium, vitamin D and parathyroid hormone.

A patient can have abnormal phosphate levels and never know it, but calcium imbalance can cause a long list of symptoms. There is a connection between phosphate and calcium levels, so doctors often order the test as a follow-up to an abnormal blood calcium measurement.

Normal Value Range

  • Negative Pregnancy Adult: 2.5 to 4.3 mg/dL or 0.81 to 1.39 mmol/L
  • Pregnancy Trimester One: 3.1 to 4.6 mg/dL or 1 to 1.49 mmol/L
  • Pregnancy Trimester Two: 2.5 to 4.6 mg/dL or 0.81 to 1.49 mmol/L
  • Pregnancy Trimester Three: 2.8 to 4.6 mg/dL or 0.9 to 1.49 mmol/L

If phosphorus levels measure lower than normal the doctor may look at diuretic abuse, hypothyroidism, rickets, alcoholism or malnutrition. On the flip side, higher than normal levels could be indicative of kidney failure or overuse of phosphate-containing supplements.

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