Is a Serum Phosphorous Test?
Phosphorus is an important element that is vital to several of
your body’s physiologic processes. It helps with bone growth, energy storage,
and nerve and muscle production. Many foods — especially meat and dairy
products — contain phosphorus, so it’s usually easy to get enough of this
mineral in your diet.
Your bones and teeth contain most of your body’s phosphorus. However,
some phosphorous is in your blood. Your doctor can assess your blood phosphorus
level using a serum phosphorus test.
when you have too much phosphorus in your blood. Hypophosphatemia is the opposite: having too little
phosphorus. Various conditions, including liver disease and vitamin D
deficiency, can cause your blood phosphorus level to become too high or too
A serum phosphorus test can determine whether you have high or
low phosphorus levels, but it can’t help your doctor diagnose the cause of your
condition. Your doctor will need to perform more tests to determine what’s
causing abnormal serum phosphorus test results.
Do I Need a Serum Phosphorus Test?
Your doctor may order a serum phosphorus test if they suspect that
your phosphorus level is too low or too high. Either extreme can lead to health
Symptoms that may indicate your phosphorus level is too low
- changes in your mental state (e.g. anxiety,
irritability, or confusion)
- bone issues, such as pain, fragility, and poor
development (in children)
- irregular breathing
- loss of appetite
- muscle weakness
- weight gain or loss
If the level of phosphorus in your blood is too high, you may
have deposits of phosphorus (combined with calcium) in your muscles. This is
rare and only occurs in people with severe calcium absorption or kidney
problems. More commonly, excess phosphorus leads to cardiovascular disease or
osteoporosis (weakening of your bones).
Your doctor may also order a serum phosphorus test if you
received abnormal results from a blood calcium test. Your body needs to
maintain a delicate balance between levels of calcium and phosphorus. An
abnormal result on a calcium test may indicate that your phosphorus levels are
Are the Risks Associated with a Serum Phosphorus Test?
As with any blood test, there’s a slight risk of bruising,
bleeding, or infection at the puncture site. You may also feel lightheaded
after having blood drawn.
In rare cases, your vein may swell after blood is drawn. This is
known as phlebitis. Applying a warm compress to the site several times a day
can ease the swelling.
Do I Prepare for a Serum Phosphorus Test?
Many medications can affect your phosphorus levels, including
antacids, vitamin D supplements (when taken in excess), and intravenous
glucose. Medications that contain sodium phosphate can also affect your
phosphorus levels. Be sure to tell your doctor about any medications you’re
taking. They may instruct you to temporarily stop using medications that could
interfere with your test results.
Is the Procedure for a Serum Phosphorus Test?
You don’t typically need to fast before this test. Your doctor
will let you know if they want you to fast for any reason.
The test involves a simple blood draw. Your doctor or a nurse
will use a small needle to collect a sample of blood from a vein in your arm or
hand. They’ll send the sample to a laboratory for analysis.
Do the Results Mean?
Serum phosphorus is measured in milligrams of phosphorus per
deciliter of blood (mg/dL). A normal range (in adults) is generally 2.5 to 4.5
The normal range varies slightly depending on your age. It’s natural
for children to have higher phosphorus levels because they need more of this
mineral to help their bones develop.
Excess phosphorus will likely build up in your bloodstream if you
have impaired kidney function. Avoiding high-phosphorus foods, such as milk,
nuts, beans, and liver, can help lower your phosphorus levels.
Besides reduced kidney function, high phosphorus levels may be due
- certain medications, such as laxatives that
- dietary problems, such as consuming too much
phosphate or vitamin D
- diabetic ketoacidosis (when your body runs out
of insulin and begins to burn fatty acids instead)
- hypocalcemia (low serum calcium levels)
- hypoparathyroidism (impaired thyroid gland
function, leading to low levels of thyroid hormone)
- liver disease
Low phosphorus levels may be due to a range of nutritional
problems and medical conditions, including:
- chronic use of antacids
- lack of vitamin D
- not getting enough phosphorus in your diet
- hypercalcemia (high serum calcium levels)
- hyperparathyroidism (an overactive thyroid
gland, leading to high levels of thyroid hormone)
- severe burns
Your doctor will analyze your results and discuss them with you.
Be sure to ask your doctor any questions you have about your results.