What are the other Names for this Test? (Equivalent Terms)
- Ionized Calcium Test
- Serum Calcium Test
- Total Calcium Test
What is Calcium Test? (Background Information)
Calcium is the most abundant mineral in the human body. About 99% of the body’s calcium is present in the bones, while the remaining 1% is present in the blood; roughly half as ionized/free/metabolically active calcium, and the other half as inactive/bound (to the protein albumin) calcium.
Calcium plays a number of roles in the functioning of the human body. These include:
- Strengthening of bones and teeth
- Contraction of the heart
- Skeletal muscle contraction
- Transmission of signals from nerves
- Clotting of blood
There exists a balance between the calcium in blood and the calcium that is stored in the bones. Even in blood, there is equilibrium between the bound and free forms of calcium. Calcium levels in the body are also regulated by:
- Dietary calcium
- Hormones, such as parathyroid hormone (PTH, produced by the parathyroid glands), calcitonin (produced by the thyroid), estrogen
- Vitamin D
- Phosphate levels
This balance is necessary, as alterations in the levels of calcium can have many consequences, such as:
- Muscle cramps, abdominal cramps, tingling sensation in the digits, or numbness around the mouth, all due to low calcium levels
- Decrease of bone mineral density (osteoporosis) making the bones prone to fractures easily, caused by long-term calcium decrease
- Kidney stones, bone pain or fractures, abdominal pain, fatigue, tiredness, or constipation, caused by high calcium levels
- Sudden changes of calcium levels can also affect the contraction of the heart
Calcium levels in blood are often measured through basic/comprehensive metabolic panels (tests) to diagnose/monitor a number of diseases, concerned with the kidneys, bones, nerves, heart, or teeth, as well as, in critically ill patients, in whom calcium fluctuations can have significant adverse consequences.
Calcium levels are often measured along with levels of phosphates, PTH, and vitamin D. While total calcium value is the measure that is usually estimated; in the following cases ionized calcium values are measured:
- Critically ill patients
- Those undergoing major surgeries
- Those requiring transfusions
- Patients with low albumin levels in blood
Urine calcium measurements are usually done over a span of 24 hours. These help in assessing, if the kidneys are excreting the right amount of calcium.
What are the Clinical Indications for performing the Calcium Test?
Blood calcium is often estimated as part of a general medical examination. It is included under the basic metabolic panel/comprehensive metabolic panel of tests, performed during a routine health screening.
A healthcare provider may order a Calcium Test, in the following scenarios:
- When an individual is known/suspected to have some kidney disease, diseases of the parathyroid gland, pancreatitis (inflammation of the pancreas), thyroid, or intestinal conditions
- Individuals presenting with symptoms of increased calcium, such as kidney stones, bone pain or fractures, abdominal pain, fatigue, tiredness, constipation, or increased urination
- Individuals presenting with symptoms of decreased calcium, such as muscle cramps, abdominal cramps, tingling sensation in digits, or numbness around the mouth
- Calcium levels are monitored with certain kinds of cancer (lungs, breast, kidney, head & neck, and multiple myeloma), as well as in those being treated for abnormal calcium levels, to assess response to treatment
- Sometimes, an abnormal EKG (electrocardiogram) may warrant a Calcium Test
- Individuals with symptoms of kidney stones (nephrolithiasis), such as pain on one side of the lower back/lower abdomen, burning urination or blood in urine. In such cases, the urine calcium levels may be determined
How is the Specimen Collected for Calcium Test?
Sample required: Blood; urine for estimating urinary calcium
- Blood sample is drawn through a needle inserted into the vein (arm)
- For urinary testing, a 24-hour urine sample is collected. From the beginning of the 24 hour period, every urine sample is collected in a container and kept refrigerated in between collections. This may be done even at home
Preparation required: Individuals are generally advised to avoid calcium supplements for 8-12 hours, before testing for calcium in blood.
What is the Significance of the Calcium Test Result?
The normal range of calcium values, called the reference range, may vary slightly amongst different laboratories. Each laboratory may show the reference range used by them. A physician interprets the results based on the reference values provided.
One such standard reference range is:
- Total calcium: 8.8-10.4 mg/dL or 2.2-2.6 mmol/L
- Ionized calcium: 4.65-5.28 mg/dL or 1.16-1.32 mmol/L
- Total calcium: 6.7-10.7 mg/dL or 1.90-2.75 mmol/L
- Ionized calcium: 4.80-5.52 mg/dL or 1.20-1.38 mmol/L
The reference range for urine calcium varies, depending on the amount of calcium in the diet.
Some of the causes for a high value of blood calcium (hypercalcemia) include:
- Hyperparathyroidism (overactive parathyroid gland)
- Diseases affecting the lung, such as sarcoidosis, tuberculosis
- Kidney transplant
- Prolonged bed rest or being kept immobilized for a long duration
- A condition called Paget’s disease that affects the bone
Some of the causes for a low value of blood calcium (hypocalcemia) include:
- Hypoparathyroisim (underactive parathyroid gland)
- Low levels of protein in blood
- Kidney failure
- Deficiency of calcium, vitamin D, or magnesium
- Increased levels of phosphates in the body
These conditions also produce corresponding changes in urine calcium levels. However, in one condition called idiopathic familial hypocalciuric hypercalcemia, the blood calcium levels are elevated, but urine calcium levels remains low.
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- Medications, like diuretics alter blood calcium levels
- The recommended daily intake of calcium for adults ranges between 1000-1300 mg, depending on the age
- Some good dietary sources of calcium include milk and other dairy products; vegetables like broccoli, spinach and okra (ladies finger); nuts like almonds and hazelnuts
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.