Table of ContentsView AllTable of ContentsResults and Possible MeaningsHow the Test Is TakenNext Steps
Table of ContentsView All
View All
Table of Contents
Results and Possible Meanings
How the Test Is Taken
Next Steps
Calciumis an essential mineral that serves many roles in the body, including bone formation, muscle movement, nerve signaling, and heart rhythm regulation.
A calcium blood test may be ordered as part of a routine checkup or to screen for or monitor medical conditions affecting the bones, kidneys, orparathyroid gland(a set of tiny organs in the neck, right next to the thyroid gland).
This article defines low, high, and normal levels of calcium in the blood in healthy individuals. It also explores possible causes and symptoms of an abnormal calcium level and what to expect during a calcium blood test.
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Calcium Blood Test Results and Possible Meanings
A calcium blood test measures the total calcium level in a person’s bloodstream. The total calcium level includes what are termed “bound” and “unbound” calcium.
Bound calcium is calcium attached to a protein, usuallyalbumin(a protein made in the liver). Unbound calcium is not attached to a protein. It’s the active form of calcium, called free or ionized calcium.
In most cases, a total calcium blood level is ordered. In specific scenarios, however, an ionized calcium blood level may be requested—for example, in people who are malnourished, critically ill, or havechronic kidney disease.
Low Calcium Levels
Alow calcium level(hypocalcemia) is less than 8.5 milligrams per deciliter (mg/dL).
Depending on the severity and duration of the hypocalcemia, symptoms range from mild to life-threatening.Frequent symptoms include numbness around the mouth, tingling in the hands and feet, andmuscle cramps and spasms. More severe symptoms include seizures and heart failure.
Surgicalhypoparathyroidismdescribes an underactive parathyroid gland and is the most common cause of low calcium levels. Surgical hypoparathyroidism may occur after an operation on the parathyroid gland,thyroid gland, or neck—for example, to treathead and neck cancer.
Function of the Parathyroid GlandThe parathyroid gland produces parathyroid hormone (PTH). Along with vitamin D, PTH interacts with a person’s bones, kidneys, and gut to maintain steady calcium levels in the bloodstream.
Function of the Parathyroid Gland
The parathyroid gland produces parathyroid hormone (PTH). Along with vitamin D, PTH interacts with a person’s bones, kidneys, and gut to maintain steady calcium levels in the bloodstream.
Other possible causes of hypocalcemia include:
Normal Calcium Levels
A normal blood calcium level is between 8.5 and 10.5 mg/dL. Keep in mind that calcium reference ranges may differ slightly depending on the laboratory being used to process the blood test.
Also, although it’s unknown precisely why, blood calcium levels vary slightly among different age groups. Specifically, blood calcium levels are a bit higher in children than in adults.
High Calcium Levels
A mildlyhigh calcium level(hypercalcemia) is between 10.5 and 11.9 mg/dL. Moderate hypercalcemia is between 12.0 and 13.9 mg/dL, whereas severe hypercalcemia is greater than 14.0 mg/dL.
Most cases of high calcium levels are detected incidentally and cause no or mild symptoms like loss of appetite, nausea, constipation, fatigue, anxiety, and excessive urination (polyuria).
Long-term elevation of calcium levels or levels that continue to rise may cause weakness, weight loss,kidney stones, or kidney injury. Severe hypercalcemia is associated with life-threatening problems likeheart arrhythmia(irregular or abnormal heartbeat), confusion, andcoma.
There are several possible causes of high calcium blood levels, although the vast majority are due to either primary hyperparathyroidism or hypercalcemia of malignancy (cancer).
Primary hyperparathyroidismdescribes an overactive parathyroid gland, resulting in excess PTH production.
Hypercalcemia of malignancyaffects an estimated 30% of people with cancer and is particularly common in individuals with advanced cancer.
Another cause of hypercalcemia of malignancy is the spread (metastasis) of cancer cells into bone. This invasion into bone releases calcium into the bloodstream.
Cancers Linked to Hypercalcemia of MalignancyIn the United States, common cancers associated with hypercalcemia of malignancy arebreast,lung,multiple myeloma, head and neck,kidney,ovarian, and certainlymphomas.
Cancers Linked to Hypercalcemia of Malignancy
In the United States, common cancers associated with hypercalcemia of malignancy arebreast,lung,multiple myeloma, head and neck,kidney,ovarian, and certainlymphomas.
Other possible causes of hypercalcemia levels include:
Routine Blood Work With Calcium Biomarkers
Low and high calcium levels can be detected with a routine blood test called abasic metabolic panel(BMP) or acomprehensive metabolic panel(CMP).
What Does a BMP and CMP Measure?A BMP measures the following:CalciumBlood glucose (sugar)SodiumPotassiumCarbon dioxideChlorideBlood urea nitrogen(BUN)CreatinineIn addition to the components measured in a BMP, a CMP also measures:AlbuminTotal proteinBilirubinLiver enzymes
What Does a BMP and CMP Measure?
A BMP measures the following:CalciumBlood glucose (sugar)SodiumPotassiumCarbon dioxideChlorideBlood urea nitrogen(BUN)CreatinineIn addition to the components measured in a BMP, a CMP also measures:AlbuminTotal proteinBilirubinLiver enzymes
A BMP measures the following:
In addition to the components measured in a BMP, a CMP also measures:
A BMP or CMP can be obtained at a healthcare provider’s office, clinic, hospital, or lab. It usually takes just minutes to draw the blood.
During a BMP or CMP blood draw, aphlebotomistperforms the following steps:
Overview of Routine Blood Tests
Before Having Blood Drawn
There may be no preparation needed before undergoing a BMP or CMP.However, if your healthcare provider is evaluating lab values such as blood glucose, you may be asked to fast, which means not eating or drinking (except water) for 8 to 12 hours before the test.
Your healthcare provider may also ask you to stop taking certain medications, vitamins, or supplements to ensure the most accurate test results.
Next Steps With Calcium Blood Test Results
Although laboratories vary, BMP and CMP test results should return within 24 hours. Be sure to reach out to your healthcare provider to discuss your results.
If you have a low or high calcium level, your healthcare provider will likely repeat the test to confirm the abnormal finding. They may also order an ionized calcium level (the active form of calcium) to obtain a complete picture of your calcium status.
When a low or high calcium level is confirmed, a healthcare provider will order additional blood tests based on factors like symptoms, family history, and use of various medications, vitamins, and supplements.
The degree of calcium abnormality and how quickly the level rose or dropped (if prior calcium blood values are available) will also be considered.
Examples of such follow-up blood tests include:
Summary
Calcium is vital to bone health and muscle, nerve, and heart functioning. Calcium levels in the bloodstream can be measured with a routine blood test, usually a basic metabolic panel (BMP) or comprehensive metabolic panel (CMP).
A low calcium level (hypocalcemia) is most commonly due to surgical hypoparathyroidism—surgery within the neck causing the parathyroid gland to become underactive. Additional causes include vitamin D and magnesium deficiency, among others.
The two most common causes of a high calcium level (hypercalcemia) are primary hyperparathyroidism—an overactive parathyroid gland—and hypercalcemia of malignancy, which is when cancer cells cause calcium from bones to leak into the bloodstream.
Speak with a healthcare provider if you have an abnormal calcium blood level. More blood tests are usually performed to confirm the finding and help diagnose the cause.
16 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Aberegg SK.Ionized calcium in the ICU: Should it be measured and corrected?Chest. 2016;149(3):846-55. doi:10.1016/j.chest.2015.12.001National Institutes of Health Office of Dietary Supplements.Calcium.Pepe J, Colangelo L, Biamonte F, et al.Diagnosis and management of hypocalcemia.Endocrine. 2020;69(3):485-495. doi:10.1007/s12020-020-02324-2Song L.Calcium and bone metabolism indices.Adv Clin Chem. 2017;82:1-46. doi:10.1016/bs.acc.2017.06.005Schafer AL, Shoback DM.Hypocalcemia: diagnosis and treatment. In: Feingold KR, Anawalt B, Blackman MR, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.Koek WNH, Campos-Obando N, van der Eerden BCJ, et al.Age-dependent sex differences in calcium and phosphate homeostasis.Endocr Connect. 2021;10(3):273-282. doi:10.1530/EC-20-0509Stokes VJ, Nielsen MF, Hannan FM, Thakker RV.Hypercalcemic disorders in children.J Bone Miner Res. 2017;32(11):2157-2170. doi:10.1002/jbmr.3296Feldenzer KL, Sarno J.Hypercalcemia of malignancy.J Adv Pract Oncol. 2018;9(5):496-504.Walker MD, Shane E.Hypercalcemia: a review.JAMA. 2022;328(16):1624-1636. doi:10.1001/jama.2022.18331Bilezikian JP, Bandeira L, Khan A, Cusano NE.Hyperparathyroidism.Lancet. 2018;391(10116):168-178. doi:10.1016/S0140-6736(17)31430-7Gastanaga VM, Schwartzberg LS, Jain RK, et al.Prevalence of hypercalcemia among cancer patients in the United States.Cancer Med. 2016;5(8):2091-2100. doi:10.1002/cam4.749Sell J, Ramirez S, Partin M.Parathyroid disorders.Am Fam Physician. 2022;105(3):289-298MedlinePlus.Basic metabolic panel (BMP).MedlinePlus.Comprehensive metabolic panel.MedlinePlus.Venipuncture.MedlinePlus.Calcium blood test.
16 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Aberegg SK.Ionized calcium in the ICU: Should it be measured and corrected?Chest. 2016;149(3):846-55. doi:10.1016/j.chest.2015.12.001National Institutes of Health Office of Dietary Supplements.Calcium.Pepe J, Colangelo L, Biamonte F, et al.Diagnosis and management of hypocalcemia.Endocrine. 2020;69(3):485-495. doi:10.1007/s12020-020-02324-2Song L.Calcium and bone metabolism indices.Adv Clin Chem. 2017;82:1-46. doi:10.1016/bs.acc.2017.06.005Schafer AL, Shoback DM.Hypocalcemia: diagnosis and treatment. In: Feingold KR, Anawalt B, Blackman MR, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.Koek WNH, Campos-Obando N, van der Eerden BCJ, et al.Age-dependent sex differences in calcium and phosphate homeostasis.Endocr Connect. 2021;10(3):273-282. doi:10.1530/EC-20-0509Stokes VJ, Nielsen MF, Hannan FM, Thakker RV.Hypercalcemic disorders in children.J Bone Miner Res. 2017;32(11):2157-2170. doi:10.1002/jbmr.3296Feldenzer KL, Sarno J.Hypercalcemia of malignancy.J Adv Pract Oncol. 2018;9(5):496-504.Walker MD, Shane E.Hypercalcemia: a review.JAMA. 2022;328(16):1624-1636. doi:10.1001/jama.2022.18331Bilezikian JP, Bandeira L, Khan A, Cusano NE.Hyperparathyroidism.Lancet. 2018;391(10116):168-178. doi:10.1016/S0140-6736(17)31430-7Gastanaga VM, Schwartzberg LS, Jain RK, et al.Prevalence of hypercalcemia among cancer patients in the United States.Cancer Med. 2016;5(8):2091-2100. doi:10.1002/cam4.749Sell J, Ramirez S, Partin M.Parathyroid disorders.Am Fam Physician. 2022;105(3):289-298MedlinePlus.Basic metabolic panel (BMP).MedlinePlus.Comprehensive metabolic panel.MedlinePlus.Venipuncture.MedlinePlus.Calcium blood test.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Aberegg SK.Ionized calcium in the ICU: Should it be measured and corrected?Chest. 2016;149(3):846-55. doi:10.1016/j.chest.2015.12.001National Institutes of Health Office of Dietary Supplements.Calcium.Pepe J, Colangelo L, Biamonte F, et al.Diagnosis and management of hypocalcemia.Endocrine. 2020;69(3):485-495. doi:10.1007/s12020-020-02324-2Song L.Calcium and bone metabolism indices.Adv Clin Chem. 2017;82:1-46. doi:10.1016/bs.acc.2017.06.005Schafer AL, Shoback DM.Hypocalcemia: diagnosis and treatment. In: Feingold KR, Anawalt B, Blackman MR, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.Koek WNH, Campos-Obando N, van der Eerden BCJ, et al.Age-dependent sex differences in calcium and phosphate homeostasis.Endocr Connect. 2021;10(3):273-282. doi:10.1530/EC-20-0509Stokes VJ, Nielsen MF, Hannan FM, Thakker RV.Hypercalcemic disorders in children.J Bone Miner Res. 2017;32(11):2157-2170. doi:10.1002/jbmr.3296Feldenzer KL, Sarno J.Hypercalcemia of malignancy.J Adv Pract Oncol. 2018;9(5):496-504.Walker MD, Shane E.Hypercalcemia: a review.JAMA. 2022;328(16):1624-1636. doi:10.1001/jama.2022.18331Bilezikian JP, Bandeira L, Khan A, Cusano NE.Hyperparathyroidism.Lancet. 2018;391(10116):168-178. doi:10.1016/S0140-6736(17)31430-7Gastanaga VM, Schwartzberg LS, Jain RK, et al.Prevalence of hypercalcemia among cancer patients in the United States.Cancer Med. 2016;5(8):2091-2100. doi:10.1002/cam4.749Sell J, Ramirez S, Partin M.Parathyroid disorders.Am Fam Physician. 2022;105(3):289-298MedlinePlus.Basic metabolic panel (BMP).MedlinePlus.Comprehensive metabolic panel.MedlinePlus.Venipuncture.MedlinePlus.Calcium blood test.
Aberegg SK.Ionized calcium in the ICU: Should it be measured and corrected?Chest. 2016;149(3):846-55. doi:10.1016/j.chest.2015.12.001
National Institutes of Health Office of Dietary Supplements.Calcium.
Pepe J, Colangelo L, Biamonte F, et al.Diagnosis and management of hypocalcemia.Endocrine. 2020;69(3):485-495. doi:10.1007/s12020-020-02324-2
Song L.Calcium and bone metabolism indices.Adv Clin Chem. 2017;82:1-46. doi:10.1016/bs.acc.2017.06.005
Schafer AL, Shoback DM.Hypocalcemia: diagnosis and treatment. In: Feingold KR, Anawalt B, Blackman MR, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.
Koek WNH, Campos-Obando N, van der Eerden BCJ, et al.Age-dependent sex differences in calcium and phosphate homeostasis.Endocr Connect. 2021;10(3):273-282. doi:10.1530/EC-20-0509
Stokes VJ, Nielsen MF, Hannan FM, Thakker RV.Hypercalcemic disorders in children.J Bone Miner Res. 2017;32(11):2157-2170. doi:10.1002/jbmr.3296
Feldenzer KL, Sarno J.Hypercalcemia of malignancy.J Adv Pract Oncol. 2018;9(5):496-504.
Walker MD, Shane E.Hypercalcemia: a review.JAMA. 2022;328(16):1624-1636. doi:10.1001/jama.2022.18331
Bilezikian JP, Bandeira L, Khan A, Cusano NE.Hyperparathyroidism.Lancet. 2018;391(10116):168-178. doi:10.1016/S0140-6736(17)31430-7
Gastanaga VM, Schwartzberg LS, Jain RK, et al.Prevalence of hypercalcemia among cancer patients in the United States.Cancer Med. 2016;5(8):2091-2100. doi:10.1002/cam4.749
Sell J, Ramirez S, Partin M.Parathyroid disorders.Am Fam Physician. 2022;105(3):289-298
MedlinePlus.Basic metabolic panel (BMP).
MedlinePlus.Comprehensive metabolic panel.
MedlinePlus.Venipuncture.
MedlinePlus.Calcium blood test.
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