Know the basics

What is Calcium blood test?

A test for calcium in the blood checks the calcium level in the body that is not stored in the bones. Calcium is the most common mineral in the body and one of the most important. The body needs it to build and fix bones and teeth, help nerves work, make muscles squeeze together, help blood clot, and help the heart to work. Almost all of the calcium in the body is stored in bone.

Normally the level of calcium in the blood is carefully controlled. When blood calcium levels get low (hypocalcemia), the bones release calcium to bring it back to a good blood level. When blood calcium levels get high (hypercalcemia), the extra calcium is stored in the bones or passed out of the body in urine and stool. The amount of calcium in the body depends on the amount of:

  • Calcium you get in your food.
  • Calcium and vitamin D your intestines absorb.
  • Phosphate in the body.
  • Certain hormones, including parathyroid hormone, calcitonin, and estrogen in the body.

Vitamin D and these hormones help control the amount of calcium in the body. They also control the amount of calcium you absorb from food and the amount passed from the body in urine. The blood levels of phosphate are closely linked to calcium levels and they work in opposite ways: As blood calcium levels get high, phosphate levels get low, and the opposite is also true.

It is important to get the right amount of calcium in your food because the body loses calcium every day. Foods rich in calcium include dairy products (milk, cheese), eggs, fish, green vegetables, and fruit. Most people who have low or high levels of calcium do not have any symptoms. Calcium levels need to be very high or low to cause symptoms.

Why is Calcium blood test performed?

A calcium blood test can be part of a screen for a variety of diseases and conditions, including osteoporosis, cancer, and kidney diseases. This blood test may also be required to monitor ongoing treatments of other conditions, or to check that any medications you are taking don’t have any unintended side effects.

Your doctor may order this test if he or she suspects any of the following conditions:

  • Bone diseases, such as osteoporosis or osteopenia
  • Cancer
  • Chronic kidney or liver disease
  • Disorders of the parathyroid gland
  • Malabsorption or a disorder that affects how your body absorbs nutrients
  • An over or underactive thyroid gland

Things to know before

What should I know before receiving Calcium blood test?

Newborns, especially premature and low birthweight infants, often are monitored during the first few days of life for neonatal hypocalcemia using the test for ionized calcium. This can occur because of an immature parathyroid gland and doesn’t always cause symptoms. The condition may resolve itself or may require treatment with supplemental calcium, given orally or intravenously.

Blood and urine calcium measurements cannot tell how much calcium is in the bones. A test similar to an X-ray, called a bone density or “Dexa” scan, is used for this purpose.

Taking thiazide diuretic drugs is the most common drug-induced reason for a high calcium level. Taking lithium or tamoxifen may also increase a person’s calcium level.

Know what happens

How to prepare for Calcium blood test?

Do not take calcium supplements for 8 to 12 hours before having a blood calcium test. Your doctor may tell you to temporarily stop taking certain medicines that can affect the test. Medicines include:

  • Calcium salts (may be found in nutritional supplements or antacids)
  • Lithium
  • Thiazide diuretics
  • Thyroxine
  • Vitamin D

What happens during Calcium blood test?

The health professional drawing blood will:

  • Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
  • Clean the needle site with alcohol.
  • Put the needle into the vein. More than one needle stick may be needed.
  • Attach a tube to the needle to fill it with blood.
  • Remove the band from your arm when enough blood is collected.
  • Put a gauze pad or cotton ball over the needle site as the needle is removed.
  • Put pressure to the site and then a bandage.

What happens after Calcium blood test?

An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

If you have any questions about the Calcium blood test, please consult with your doctor to better understand your instructions.

Understand the results

What do my results mean?

Normal values

Normal value ranges may vary slightly among different laboratories. Some laboratories use different measurements or may test different specimens. Talk to your doctor about the meaning of your specific test results.

Total calcium
Adults: 8.8–10.4 milligrams per deciliter (mg/dL) or 2.2–2.6 millimoles per liter (mmol/L)
Children: 6.7–10.7 milligrams per deciliter (mg/dL) or 1.90–2.75 millimoles per liter (mmol/L)

Normal blood calcium values are lower in older people. Normal blood calcium values are higher in children because their bones are growing quickly.

An ionized calcium test checks the amount of calcium that is not attached to protein in the blood. The level of ionized calcium in the blood is not affected by the amount of protein in the blood.

Ionized calcium
Adults: 4.65–5.28 mg/dL or 1.16–1.32 mmol/L
Children: 4.80–5.52 mg/dL or 1.20–1.38 mmol/L

High values

High values of calcium may be caused by:

  • Hyperparathyroidism.
  • Cancer, including cancerthat has spread to the bones.
  • Tuberculosis.
  • Being on bed restfor a long time after a broken bone.
  • Paget’s disease.

Low values

Low values of calcium may be caused by:

  • A low level of the blood protein albumin(hypoalbuminemia).
  • Hypoparathyroidism.
  • High levels of phosphate in the blood, which can be caused by kidney failure, laxative use, and other things.
  • Malnutrition caused by diseases such as celiac disease, pancreatitis, and alcoholism.
  • Osteomalacia.

Depending on the laboratory and hospital, the normal range for Calcium blood test may vary. Please discuss with your doctor any questions you may have about your test results.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Review Date: January 4, 2017 | Last Modified: January 4, 2017

Want to live your best life?
Get the Hello Doktor Daily newsletter for health tips, wellness updates and more.