Test library
Serum Calcium Test
A Calcium blood test measures the level of calcium in the bloodstream. It is used to evaluate bone health, parathyroid and kidney function, and conditions that disturb the body's mineral balance.
Order Calcium, Blood Test
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Order Calcium, Blood Test- Typical turnaround
- 1-3 business days
- Starting price
- From $29
- Results
- Confidential, online
Quick answer
The Calcium blood test measures how much calcium is circulating in the blood. Calcium supports bones, muscles, nerves, and blood clotting, and its level is tightly controlled by the parathyroid glands, vitamin D, and the kidneys. The test is often part of a routine metabolic panel and is used to investigate symptoms or conditions that affect mineral balance.
What this test measures
Calcium is a mineral that is essential for bone structure, muscle contraction, nerve signaling, and blood clotting. The body keeps blood calcium within a narrow range, drawing on stores in bone and regulating absorption and excretion through hormones such as parathyroid hormone and vitamin D. A blood test measures the calcium currently in circulation rather than the amount stored in bone.
Most calcium in the blood travels attached to proteins such as albumin, while a smaller portion circulates in a free, active form. Laboratories may report a total calcium level and, when needed, calculate a corrected value based on albumin. The test uses a blood sample drawn from a vein, and it is frequently ordered as one part of a comprehensive metabolic panel.
Clinicians order a calcium level to evaluate bone disease, parathyroid disorders, kidney disease, and symptoms such as muscle cramps, weakness, confusion, or fatigue. It is also used to monitor conditions or treatments that can shift calcium up or down. A single result is interpreted with other tests, including albumin, phosphate, and parathyroid hormone.
- Total calcium
- Ionized (free) calcium when ordered
- Albumin
- Corrected calcium
- Phosphate (phosphorus)
- Parathyroid hormone (PTH)
- Vitamin D (25-hydroxy)
- Magnesium
- Alkaline phosphatase
- Creatinine
Why people order this test
- Evaluate bone health and bone loss
- Investigate parathyroid gland function
- Monitor kidney disease and mineral balance
- Assess symptoms such as muscle cramps or weakness
- Follow up on an abnormal routine metabolic panel
- Monitor conditions or treatments that affect calcium
How to prepare
Fasting may be requested if the calcium test is bundled with other tests such as a lipid or glucose panel. A blood sample is drawn from a vein, usually at the arm. Follow the preparation instructions provided with the order.
Understanding your results
Results are typically available within one to three business days. A value outside the reference range may reflect a problem with the parathyroid glands, kidneys, bones, or vitamin D, but it does not diagnose a condition on its own. A healthcare provider interprets it with other results and the clinical picture.
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Frequently Asked Questions
What does a calcium blood test measure?
It measures the amount of calcium circulating in the blood. Most of the body's calcium is stored in bone, so a blood level reflects the portion in circulation rather than total body stores.
Do I need to fast?
Fasting is usually not required for calcium alone, but it may be requested if the test is combined with a lipid or glucose panel. Follow the instructions supplied with your order.
Why is albumin tested with calcium?
Much of the calcium in blood travels bound to albumin. Measuring albumin helps the laboratory interpret the total calcium value and calculate a corrected level when needed.
What can cause a high calcium level?
High calcium can be related to the parathyroid glands, certain medications, or other conditions. A healthcare provider evaluates the cause with additional tests.
What can cause a low calcium level?
Low calcium can be linked to vitamin D deficiency, kidney problems, low albumin, or other factors. The result is interpreted alongside related tests.
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