Abnormal phosphorus levels in the blood do not usually cause any particular symptoms, except in certain extreme conditions. In the differential diagnosis of calcium level abnormalities, a phosphate level measurement is generally ordered at the same time as a calcium level test, and sometimes at the same time as parathyroid hormone (PTH) and Vitamin D tests. Blood phosphate level is controlled by dietary intake (including supplements) and by proper kidney and parathyroid gland function.
Higher than normal phosphate levels are found mainly in the presence of kidney disease, liver disease, underactive parathyroid glands, Vitamin D intoxication, or excessive dietary intake of phosphates caused by supplements.
In outpatients, lower blood phosphate levels may be caused by overactive parathyroid glands, some diuretics, malnutrition, or alcoholism. Underactive thyroid glands, Vitamin D deficiency causing rickets in children or osteomalacia in adults (two bone disorders), chronic use of antacids, or a potassium or magnesium deficiency may also be involved.