The examination of phosphorus in the blood is usually done together with the measurement of calcium, parathyroid hormone or vitamin D and aims to assist the diagnosis and assist in the monitoring of diseases involving the kidneys or gastrointestinal tract.
Phosphorus is a mineral that can be obtained through food and helps in the process of forming teeth and bones, in the functioning of muscles and nerves and in the supply of energy. Adequate levels of phosphorus in the blood of adults is between 2.5 and 4.5 mg / dL, values above or below should be investigated and the cause treated by the doctor.
How is done
The blood phosphorus test is done by collecting a small amount of blood in an artery in the arm. The collection must be done with the person fasting for at least 4 hours. In addition, it is important to inform the use of medications, such as contraceptives, antibiotics, such as isoniazid, or antihistamines, such as promethazine, for example, as they may interfere with the test result.
The collected blood is sent to the laboratory, where the dosage of phosphorus in the blood will be made. Usually the doctor orders a blood phosphorus test together with the dosage of calcium, vitamin D and PTH, as these are factors that interfere with the concentration of phosphorus in the blood. Learn more about the PTH exam.
Blood phosphorus testing is usually recommended when there are altered levels of calcium in the blood, when problems in the gastrointestinal or renal tract are suspected, or when the person has symptoms of hypocalcaemia, such as cramps, sweating, weakness and tingling in the mouth, hands and feet. Understand what hypocalcemia is and what it can cause.
Reference values
The reference values of phosphorus in the blood vary according to age with the laboratory where the test was performed, which can be:
| Age | Reference value |
| 0 - 28 days | 4.2 - 9.0 mg / dL |
| 28 days to 2 years | 3.8 - 6.2 mg / dL |
| 2 to 16 years | 3.5 - 5.9 mg / dL |
| From 16 years | 2.5 - 4.5 mg / dL |
What does high phosphorus mean
High blood phosphorus, also called hyperphosphatemia, can be due to:
- Hypoparathyroidism, since PTH is found in low concentrations, the levels of calcium and phosphorus in the blood are not properly regulated, since PTH is responsible for this regulation; Renal failure, since the kidneys are responsible for eliminating excess phosphorus in the urine, thus accumulating in the blood; Use of supplements or medications that contain phosphate; Menopause.
The accumulation of phosphorus in the blood can lead to injuries of various organs by calcifications and, thus, cardiovascular problems, for example.
What does low phosphorus mean
Phosphorus in low blood concentrations, also called hypophosphatemia, can happen due to:
- Vitamin D deficiency, as this vitamin helps the intestines and kidneys to absorb phosphorus; Malabsorption; Low intake of phosphorus in the diet; Hypothyroidism; Hypokalemia, which is a low concentration of potassium in the blood; Hypocalcemia, which is the low concentration of calcium in the blood.
Very low levels of phosphorus in the blood of children can interfere with bone growth, so it is important that the child has a balanced diet that involves the consumption of foods rich in phosphorus, such as sardines, pumpkin seeds and almonds, for example. See other phosphorus-rich foods.
