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Phosphorus Test: Why and How is it Done?

Phosphorus Test: Why and How is it Done?

Phosphorus is a mineral that helps in the production of protein and energy required for the proper functioning of muscles and nerves. It helps to form bones and teeth. The mineral occurs in the blood in the form of organically bound phosphoric acid and inorganic phosphate. It is one of the most essential minerals for the growth and maintenance of cells and tissues as it helps in the production of DNA and RNA.

A phosphorus test helps to measure the amount of phosphorus in the blood and to aid the diagnosis of the condition related to abnormal levels of phosphorus, including osteoporosis.

The test is often accompanied by other tests including calcium, parathyroid hormone, or vitamin D. The tests further help to diagnose or monitor treatments of various health conditions caused because of calcium and phosphorus imbalance.

A phosphorus test or P+ test is usually done on blood samples. In some cases, healthcare professionals screen urine samples to check phosphorus elimination by the kidneys.

Please note that enemas, consumption of vitamin D supplements in excess quantity, and intravenous glucose administration may affect phosphorus levels in the blood and urine.

The normal range of a phosphorus test may vary based on the laboratories. On average, a normal phosphorus range for adults is between 2.3 to 4.7 mg/dL.

Abnormal levels of phosphorus can cause a number of health conditions. High levels of phosphorus can also cause organ damage because of the accumulation of calcium phosphate in the tissues. In some cases, high levels of phosphorus can also cause osteoporosis or cardiovascular disease.

Just like any other blood test, after a phosphorus test, you may experience slight dizziness, bleeding, or pain from the puncture site. Talk to your doctor if you have any other queries.

Why is a Phosphorus Test done?

Phosphorus is absorbed in the intestines and is filtered and eliminated via your kidneys. Abnormal levels of phosphorus in your blood indicate that you may have kidney disease, liver disease, weakness, fatigue, or bone problems.

Your doctor may ask you to do a phosphorus test in the following conditions:

  • If you have issues with diabetes that includes hormone imbalances
  • If you have bone issues
  • In the case of muscle cramping
  • If instances of fatigue
  • If you have muscle weakness

Your doctor may ask you to do additional blood tests if you have abnormal phosphorus levels. Based on the reports of the additional tests your doctor may suggest treatments.

Prerequisites of a Phosphorus Test

Inform your doctor about all the prescriptions and over-the-counter medications, herbals, and supplements you take. Your doctor may ask you to change the dosage or stop the medications for a certain period. Do not change the dosage or stop the medications without informing the doctor.

You may need to fast overnight before the P+ test.

Your doctor will also ask you to avoid certain medicines until the test is over.

Your doctor may ask you to avoid a few foods and drinks including chocolate, fish, cheese, beans, and beer that may affect your results.

Phosphorus test is a safe procedure that involves little to no risks. In some cases, you may feel lightheaded after the test. Talk to your doctor if you have any queries.

You may also have bruises or mild soreness on the puncture site after the test that can last for a few days. Seek immediate medical help if the discomfort worsens.

phosphorus test

Understanding the Results

For adults, a normal phosphorus range is between 2.3 to 4.7 mg/dL. For kids, a normal phosphorus range is between 4.0 to 7.0 mg/dL.

The normal range may vary amongst different laboratories. Discuss with your doctor about your specific tests results.

If you have low or high levels of phosphorus, it indicates certain health conditions.

Low levels of phosphorus (hypophosphatemia) in the blood may indicate the following conditions:

High levels of phosphorus (hyperphosphatemia) in the blood may indicate the following health conditions:

  • Liver disease
  • Kidney disease
  • Cardiovascular disease
  • Hypoparathyroidism
  • Osteoporosis
  • Excess consumption of phosphate or vitamin D supplements

If you have been diagnosed with high levels of phosphorus, your doctor may ask you to do a few other tests to understand the source and suggest the course of treatments.

When should a phosphorus test be repeated?

You will be asked to repeat the phosphorus test if you are undergoing treatment for abnormal calcium levels because of uncontrolled diabetes or kidney disease.

It is also advised to repeat phosphorus tests to check calcium or phosphate levels if you are consuming calcium or phosphate supplements.


The health expert at the lab will clean the area. They may wrap a band around your arm. This will help your veins become visible. A blood sample is drawn with the help of a small needle. Once the blood is drawn, the technician will take off the band tied around your arm.

A cotton ball or a bandage will be applied to the punctured area. The collected blood will be sent for analysis.

In some cases, once the blood is drawn, you may feel slight pain and dizziness.

Seek medical advice for any concerns during the P+ test.

Learn more about osteoporosis screening and diagnosis here.

Hello Health Group does not provide medical advice, diagnosis or treatment.


Phosphorus blood test/https://medlineplus.gov/ency/article/003478.htm/Accessed October 20, 2021

Phosphorus/https://labtestsonline.org/tests/phosphorus/Accessed October 20, 2021

Phosphorus test/https://www.uclahealth.org/endocrine-center/phosphorus-test/Accessed October 20, 2021

Phosphorus blood test/https://www.mountsinai.org/health-library/tests/phosphorus-blood-test/Accessed October 20, 2021

Phosphate in blood

https://medlineplus.gov/lab-tests/phosphate-in-blood/ Accessed October 20, 2021

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Written by Nikita Bhalla Updated Oct 20
Fact Checked by Bianchi Mendoza, R.N.