Ionized Calcium

What is ionized calcium?

Ionized calcium refers to calcium in your blood that isn’t attached to proteins. It makes up about half of all the calcium in your blood. Another name for ionized calcium is “free calcium” because it’s active and available for use. The rest of the calcium in your blood attaches to proteins (mostly albumin). Healthcare providers call this “bound calcium” because it’s inactive and unusable.

Ionized calcium plays a major role in your body’s health. It supports your:

• Nerves.
• Muscles.
• Heart.
• Blood-clotting ability.

Your body stores 99% of its calcium supply in your bones and teeth. The other 1% circulates in your blood. That means ionized (free) calcium makes up about 0.5% of the calcium in your entire body. That may not seem like much, but ionized calcium is essential for overall health. If you have too much or too little in your blood, it could point to an underlying health condition.

What tests will be done to measure ionized calcium in my blood?

Your provider may want to run an ionized calcium test. This test differs from a standard calcium blood test, which checks the total amount of calcium in your blood (both bound and free). In contrast, an ionized calcium test only measures the free calcium in your blood.

To run the test, your provider will need a small sample of your blood.

Why would I need an ionized calcium test?

A provider might order an ionized calcium test if you:

• Have abnormal levels of blood proteins (like albumin).
• Have a serious illness and need IV fluids.
• Need major surgery.
• Receive blood transfusions.
• Are pregnant and need neonatal monitoring.
• Have acute pancreatitis symptoms.
• Have symptoms of a parathyroid disorder.

How do I prepare for an ionized calcium test?

Don’t eat or drink anything starting six hours before your test. (You can have small sips of water.) You’ll also need to tell your provider about any medications and supplements you take. Some drugs can interfere with results, so you may need to stop taking certain medications before your test. You should never stop medication unless your provider tells you it’s safe to do so.

What does ionized calcium indicate?

Your ionized calcium range can help your provider diagnose several health conditions like pancreatitis, kidney disease and parathyroid gland conditions. When you have a normal range of ionized calcium, it’s a sign that your body is working as it should.

The following table shows normal ionized calcium ranges for newborns, children and adults:

Note: These values can vary slightly depending on the laboratory.

What does low ionized calcium mean?

If you have low ionized calcium, it might indicate one of several conditions, including:

• Hypoparathyroidism (your parathyroid glands don’t make enough hormones).
• Pancreatitis (painful inflammation of your pancreas).
• Malabsorption.
• Rickets (soft bones in children).
• Kidney failure.
• Vitamin D deficiency.

Low ionized calcium symptoms

Low ionized calcium (sometimes called hypocalcemia) may cause several symptoms, like:

• Muscle cramps.
• Confusion.
• Memory loss.
• Weak, brittle nails.
• Numbness and tingling.
• Depression.

How do you fix low ionized calcium?

If you have low ionized calcium, a provider may recommend one or more of the following treatments to increase calcium levels in your body:

• Calcium supplements.
• Vitamin D supplements.
• Calcium gluconate injection.
• Parathyroid hormone (PTH) replacement.

Your provider will also recommend additional treatments for any underlying conditions.

What does high ionized calcium mean?

If you have high ionized calcium, it could point to health conditions like:

• Hyperthyroidism (overactive thyroid).
• Hyperparathyroidism (your parathyroid glands make too much hormone).
• Paget’s disease of the bone (excessive breakdown and regrowth of bone tissue).
• Thrombocytosis (high platelet count).
• Sarcoidosis (a condition that causes granulomas in various areas of your body).
• Multiple myeloma (a rare blood cancer).

High ionized calcium symptoms

High ionized calcium (sometimes called hypercalcemia) can cause a range of symptoms, including:

• Frequent urination (peeing more than usual).
• Muscle aches or cramps.
• Nausea and vomiting.
• Headaches.
• Fatigue.
• Bone pain.
• Constipation.
• Memory loss.
• Depression.
• Loss of appetite.

How do you fix high ionized calcium?

Treatment for high ionized calcium depends on the cause and may include:

• Calcimimetics (medications that help control overactive parathyroid glands).
• Calcitonin supplements (help control calcium levels in your blood).
• Bisphosphonates (osteoporosis drugs that can lower cancer-related hypercalcemia).
• Denosumab (often used in people who don’t respond to bisphosphonates).
• Prednisone (used when high levels of vitamin D cause hypercalcemia).
• IV fluids (used in severe cases, when hypercalcemia is a medical emergency).
• Parathyroidectomy (to remove affected tissue in your parathyroid glands).

Depending on the underlying cause, your healthcare provider might recommend additional treatments.

A note from Cleveland Clinic

Ionized calcium is essential for health. If you have too much or too little of it in your blood, your body can’t function properly. An ionized calcium test can’t tell you what condition you have — but it gives your healthcare provider valuable information that can lead to appropriate diagnosis and treatment.