Is an Ionized Calcium Test?
Calcium is an important mineral that your body uses in many ways.
It increases the strength of your bones and teeth and helps your muscles and
A serum calcium blood test measures the total calcium in your
blood. There are several different forms of calcium in your blood. These
include ionized calcium, calcium bound to other minerals called anions, and
calcium bound to proteins like albumin. Ionized calcium, also known as free
calcium, is the most active form.
Do I Need an Ionized Calcium Test?
A serum calcium test usually checks the total amount of calcium
in your blood. This includes ionized calcium and calcium bound to proteins.
Your doctor may want to check your blood calcium levels if you have signs of
kidney disease, certain kinds of cancers, or problems with your parathyroid
Ionized calcium levels give more information about active,
ionized calcium. It may be important to know your ionized calcium levels if you
have abnormal levels of proteins, such as albumin, or immunoglobins in your
blood. If the balance between bound calcium and free calcium isn’t normal, it’s
important to find out why. Free calcium and bound calcium each typically make
up half of your body’s total calcium. An imbalance can be a sign of a major
You may have your ionized calcium level checked if:
- you’re receiving blood transfusions
- you’re critically ill and on intravenous (IV)
- you’re having major surgery
- you have abnormal levels of blood proteins
In these cases, it’s important to understand exactly how much
free calcium you have available.
Low levels of free calcium can cause your heart to slow down or
speed up, cause muscle spasms, and even result in a coma. Your doctor may order
an ionized calcium test if you have any signs of numbness around your mouth or
in your hands and feet, or if you have muscle spasms in the same areas. These
are symptoms of low free calcium levels.
An ionized calcium test is harder to perform than a serum calcium
test. It requires special handling of the blood sample, and it’s only done in
Do I Prepare for an Ionized Calcium Test?
You’ll need to fast for six hours before you have your blood
drawn for an ionized calcium test. This means you shouldn’t eat or drink
anything other than water during that time.
Discuss your current medications with your doctor. You may have
to stop taking certain medications before the test but only if your doctor
tells you to do so. Examples of drugs that can affect your ionized calcium
- calcium salts
- thiazide diuretics
Don’t stop taking a medication without talking to your doctor
about it first.
Is an Ionized Calcium Test Performed?
An ionized calcium test uses a small amount of your blood. A
healthcare professional will get a blood sample by performing a venipuncture.
They’ll clean a section of skin on your arm or hand, insert a needle into your
vein through your skin, and then draw a small amount of blood into a test tube.
You may feel some moderate pain or a mild pinching sensation
during the procedure. After your doctor removes the needle, you may feel a
throbbing sensation. You’ll be instructed to apply pressure to the site where
the needle entered your skin. Your arm will then be bandaged. You should avoid
using that arm for heavy lifting for the rest of the day.
Are the Risks of an Ionized Calcium Test?
There are some very rare risks involved in taking a blood sample,
- lightheadedness or fainting
- hematoma, which occurs when blood accumulates
under your skin
- excessive bleeding
Bleeding for a long period after the procedure may indicate a
more serious bleeding condition.
Do the Results Mean?
Normal levels of ionized calcium are different in adults and
children. In adults, a level of 4.64 to 5.28 milligrams per deciliter (mg/dL) is
normal. In children, a normal ionized calcium level is 4.8 to 5.52 mg/dL.
If you have low levels of ionized calcium in your blood, it can
- hypoparathyroidism, which is an underactive
- inherited resistance to parathyroid hormone
- malabsorption of calcium
- a vitamin D deficiency
- osteomalacia or rickets, which is a softening of
the bones (in many cases due to a vitamin D deficiency)
- a magnesium deficiency
- high phosphorus levels
- acute pancreatitis, which is an inflammation of
- kidney failure
If you have a high level of ionized calcium in your blood, it can
- hyperparathyroidism, which is an overactive
- sedentary lifestyle or lack of mobility
- milk-alkali syndrome, which is high levels of
calcium and alkali in the body due to having too much milk or antacids over
- multiple myeloma, which is cancer of the plasma
cells (a type of white blood cell that produces antibodies)
- Paget’s disease, which is a disorder that
results in deformity due to abnormal bone destruction and growth
- sarcoidosis, which is an inflammatory disease
that affects the eyes, skin, and other organs
- tuberculosis, which is a potentially life-threatening
disease caused by the bacterium Mycobacterium tuberculosis
- a kidney transplant
- the use of thiazide diuretics
- certain kinds of tumors
- an overdose of vitamin D
Your doctor will discuss your results with you. They’ll also help
determine your next steps if any are needed.