The total calcium blood test is used to measure the total amount of calcium in your blood. Calcium is one of the most important minerals in your body. Most of your body’s calcium is stored in your bones.

Your body requires calcium to maintain healthy bones and teeth. It’s also essential for keeping your nerves, heart, and muscles functioning properly. Since calcium is so important for many of your body’s functions, its levels need to be within a tight range.

A second calcium blood test, called the ionized calcium blood test, measures the amount of “free” calcium present in your blood. “Free calcium” refers to calcium that’s not bound to any proteins and not together with an anion in your blood.

In addition to these two calcium blood tests, the level of calcium in your urine can be measured as well.

Your doctor will typically order a total calcium blood test as part of a routine metabolic panel during a general physical examination.

If you have symptoms of high or low calcium levels, your doctor may order a calcium blood test.

Your doctor may also order a calcium blood test if they suspect that you have kidney disease, parathyroid disease, cancer, or malnutrition.

Your doctor may request that you fast or stop taking certain medications or supplements before the test. These medications can include:

  • lithium
  • thiazide diuretics
  • antacids containing calcium
  • vitamin D supplements
  • calcium supplements

Be sure your doctor is aware of the medications and supplements that you’re taking so that they can give you appropriate guidelines before your test.

Additionally, consuming large amount of foods or drinks that contain calcium can increase the levels of calcium in your blood and affect test results.

To perform the test, your healthcare provider will draw a blood sample from your arm.

A needle will be inserted into a vein in your arm, and a small amount of blood will be collected into a tube. The blood draw should take less than five minutes. You may feel a slight pinch when the needle enters your arm.

Generally speaking, a normal reference range for the blood total calcium test in adults is between 8.6 and 10.2 milligrams per deciliter (mg/dL). This range can vary from lab to lab.

In order to interpret your individual test results, you should always use the reference ranges provided along with the report of your test results.

Test result values that fall above the reference range are considered high. Having a higher-than-normal blood calcium level is called hypercalcemia.

Symptoms of high calcium levels can include:

  • tiredness or weakness
  • nausea or vomiting
  • low appetite
  • abdominal pains
  • having to urinate more frequently
  • being constipated
  • excessive thirst
  • bone pain

Diseases or conditions that can cause hypercalcemia can include:

  • primary hyperparathyroidism (an overactive set of parathyroid glands) or certain types of cancer (together, these account for 80 to 90 percent of hypercalcemic cases)
  • hyperthyroidism (an overactive thyroid gland)
  • kidney or adrenal gland failure
  • sarcoidosis, an inflammatory disease that causes growths called granulomas to develop throughout your body
  • being bedridden or immobilized for a prolonged period of time
  • medications such as lithium and thiazide diuretics
  • taking too much calcium or vitamin D through supplementation

If you have hypercalcemia, your doctor will aim to identify and treat the condition that’s causing high calcium levels.

When your test result values fall below the reference range, they’re considered low. Having a low blood calcium level is called hypocalcemia.

Typically, hypocalcemia occurs when either too much calcium is lost through your urine or when not enough calcium is moved from your bones into your blood.

Symptoms of low calcium levels include:

  • cramps in your abdomen or muscles
  • a tingling sensation in your fingers
  • irregular heartbeat

Some of the potential causes of hypocalcemia include:

  • hypoparathyroidism (an underactive parathyroid gland)
  • kidney failure
  • pancreatitis (inflammation of the pancreas)
  • problems with absorption of calcium
  • certain medications, including corticosteroids, anticonvulsants, and rifampin (an antibiotic)
  • deficiency of calcium or vitamin D in your diet
  • low levels of albumin in the blood, possibly due to malnutrition or liver disease, in which the total calcium level may or may not reflect a truly hypocalcemic state

Your doctor may treat hypocalcemia through the use of calcium supplements and sometimes vitamin D supplements. If there’s an underlying disease or condition that’s causing your hypocalcemia, they’ll work to identify and treat that as well.

The total calcium blood test measures the total amount of calcium in your blood.

Your doctor will order this test as part of a routine metabolic panel or if you’re experiencing certain symptoms. Be sure to see your doctor if you’re having symptoms of low or high calcium.

In many cases, high or low results have causes that are easily treated. In other cases, you may need a more complex treatment plan to address the underlying condition. Talk to your doctor about your options. They’ll work to identify and treat the disease or condition that’s affecting your calcium levels.