A phosphorus blood test is done to assess phosphorus levels in the blood. Phosphorus, a mineral obtained mostly from food, helps:
Doctors may order a phosphorus test to help diagnose or monitor any of several conditions, including:
Kids tend to have higher phosphorus levels than adults, mainly because their bones are still growing. When there's not enough phosphorus, bone growth and other body functions may be affected. When there's too much, it can be a sign of conditions that affect the balance of minerals in the body.
No special preparations are needed for this test. However, certain drugs — especially antacids, laxatives, and diuretics — might alter the test results, so tell your doctor about any medications your child is taking.
On the day of the test, having your child wear a short-sleeve shirt can make things easier for the technician who will be drawing the blood.
A health professional will usually draw the blood from a vein. For an infant, the blood may be obtained by puncturing the heel with a small needle (lancet). If the blood is being drawn from a vein, the skin surface is cleaned with antiseptic, and an elastic band (tourniquet) is placed around the upper arm to apply pressure and cause the veins to swell with blood. A needle is inserted into a vein (usually in the arm inside of the elbow or on the back of the hand) and blood is withdrawn and collected in a vial or syringe.
After the procedure, the elastic band is removed. Once the blood has been collected, the needle is removed and the area is covered with cotton or a bandage to stop the bleeding. Collecting blood for this test will only take a few minutes.
Either method (heel or vein withdrawal) of collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick. Afterward, there may be some mild bruising, which should go away in a few days.
The blood sample will be processed by a machine. The results are commonly available after a few hours or the next day.
If phosphorus levels are found to be either elevated or deficient, further testing may be necessary to determine what's causing the problem and how to treat it.
The phosphorus test is considered a safe procedure. However, as with many medical tests, some problems can occur with having blood drawn:
Having a blood test is relatively painless. Still, many children are afraid of needles. Explaining the test in terms your child can understand might help ease some of the fear.
Allow your child to ask the technician any questions he or she might have. Tell your child to try to relax and stay still during the procedure, as tensing muscles and moving can make it harder and more painful to draw blood. It also may help if your child looks away when the needle is being inserted into the skin.
If you have questions about the phosphorus test, speak with your doctor.
Reviewed by: Steven Dowshen, MD
Date reviewed: March 2011
|National Institute of Diabetes and Digestive and Kidney Diseases This group conducts and supports research on many serious diseases affecting public health.|
|American Medical Association (AMA) The AMA has made a commitment to medicine by making doctors more accessible to their patients. Contact the AMA at: American Medical Association|
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|American Academy of Pediatrics (AAP) The AAP is committed to the health and well-being of infants, adolescents, and young adults. The website offers news articles and tips on health for families.|
|American Society of Hematology This group provides information relating to blood, blood-forming tissues, and blood diseases.|
|Blood Test: Phosphorus A phosphorus test looks at levels of phosphorus in a person's blood. Find out why doctors do this test and what's involved for teens.|
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|Kidneys and Urinary Tract The bean-shaped kidneys, each about the size of a child's fist, perform several functions essential to health. Their most important role is to filter blood and produce urine.|
|Blood Test (Video) This video shows what it's like to get a blood test.|
|Getting a Blood Test (Video) A blood test might sound scary, but it usually takes less than a minute. Watch what happens in this video for kids.|
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