Summary

This test measures the level of phosphate in your blood to help diagnose disorders that cause abnormally high or low levels of phosphate. These can be grouped as those that cause poor absorption of minerals from the intestines or interfere with the process for getting rid of minerals by the kidneys. Blood levels of calcium, magnesium, parathyroid hormone (PTH), and vitamin D may also be measured at the same time.

Why get tested?

We get the phosphate we need through the foods we eat. Most of the body's phosphates combine with calcium to help form bones and teeth. Normally, phosphate is absorbed from food in the intestines and the kidneys filter and remove excess phosphate from the blood. If phosphate levels in your blood are too high or too low, it can be a sign of an absorption problem or kidney disease.

Phosphates are vital for bone growth, energy production and muscle and nerve function.  They also play an important role as a buffer, helping to maintain the body’s acid-base balance.

High levels of blood phosphate may be due to:

• Kidney disease
• Liver disease
• Too much vitamin D
• Too much phosphate in your diet
• Use of laxatives that contain phosphate

Low levels of blood phosphate may be due to:

• Too much calcium in the body
• Primary hyperparathyroidism (one or more of the parathyroid glands make too much PTH)
• Too little dietary intake of phosphate 
• Too little vitamin D, resulting bone problems such as rickets (childhood) or osteomalacia (adult)

Having the test

Sample

A blood or timed urine sample

Any preparation?

None

Your results

Reading your test report

Your results will be presented along with those of your other tests on the same form.  You will see separate columns or lines for each of these tests.

Reference intervals

Your results will be compared to reference intervals (sometimes called a normal range).

• Reference intervals are the range of results expected in healthy people.
• When compared against them your results may be flagged high or low if they sit outside this range.
• Many reference intervals vary between labs so only those that are standardised or harmonised across most laboratories are given on this website.

If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation. Your results need to be interpreted by your doctor.

The reference intervals for this test are common reference intervals which means that the majority of laboratories in Australia should be using the same reference intervals.

Common reference intervals for phosphate

Adult

0.75- 1.50 mmol/L

Children

0 days to 1 week         1.25 - 2.85 mmol/L
1 week - 4 weeks        1.50 - 2.75 mmol/L
4 weeks - 26 weeks    1.45 - 2.50 mmol/L
26 weeks - 1 year       1.30 - 2.30 mmol/L
1 year - 4 years          1.10 - 2.20 mmol/L
4 years - 15 years       0.90 - 2.00 mmol/L
15 years - 18 years     0.80 - 1.85 mmol/L
18 years - 20 years     0.75 - 1.65 mmol/L

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms.   It is important that you tell them everything you think might help. 

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely. 

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

Any more to know?

Your doctor may tell you to temporarily stop taking medicines that may affect the test. These medicines include water pills (diuretics), antacids, and laxatives.

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

Get further trustworthy health information and advice from healthdirect.