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 (Ca) [kal´se-um]
a chemical element, atomic number 20, atomic weight 40.08. (See Appendix 6.) Calcium is the most abundant mineral in the body. In combination with phosphorus it forms calcium phosphate, the dense, hard material of the bones and teeth. It is an important cation in intracellular and extracellular fluid and is essential to the normal clotting of blood, the maintenance of a normal heartbeat, and the initiation of neuromuscular and metabolic activities.

Within the body fluids calcium exists in three forms. Protein-bound calcium accounts for about 47 per cent of the calcium in plasma; most of it in this form is bound to albumin. Another 47 per cent of plasma calcium is ionized. About 6 per cent is complexed with phosphate, citrate, and other anions.

Ionized calcium is physiologically active. One of its most important physiological functions is control of the permeability of cell membranes. Parathyroid hormone, which causes transfer of exchangeable calcium from bone into the blood stream, maintains calcium homeostasis by preventing either calcium deficit or excess.

Hypercalcemia: This is when the level of serum calcium rises above normal; neuromuscular activity begins to diminish. Symptoms include lethargy, muscle weakness (which, as the level of calcium increases, can progress to depressed reflexes and hypotonic muscles), constipation, mental confusion, and coma. The heartbeat also slows, which potentiates the effects of digitalis.

Hypocalcemia: This is a serum level of calcium that is below normal; it is manifested by increased neuromuscular irritability. When there is a deficit of ionized calcium, the nerve cells become more permeable, allowing leakage of sodium and potassium from the cells. This produces excitation of the nerve fibers and triggers uncontrollable activity of the skeletal muscles. Hence, as the calcium level continues to drop, the patient begins to experience muscle twitching and cramping, grimacing, and carpopedal spasm, which can quickly progress to tetany, laryngospasm, convulsions, cardiac arrhythmias, and eventually to respiratory and cardiac arrest. Relatively early signs of hypocalcemia are a positive trousseau's sign and a positive chvostek's sign.

Dietary sources of calcium include dairy products (such as milk and cheese), soybeans, fortified orange juice, dark green leafy vegetables (such as mustard greens and broccoli), sardines, clams, and oysters. The recommended dietary allowance of calcium for children aged 4 to 8 is 800 mg, and that for women aged 50 to 70 is 1200 mg. (See tables in the Appendices for recommended dietary allowances across the life span.) It is difficult to meet these requirements without including milk or milk products in the daily diet. The most familiar calcium deficiency disease is rickets, in which the bones and teeth soften. However, it is believed that a large number of people suffer from subclinical calcium deficiency because of poor eating habits. Since calcium is essential to the formation and maintenance of strong bones, an adequate intake is important in the prevention of osteoporosis.
calcium acetate the calcium salt of acetic acid; administered orally as a source of calcium and as a phosphate binder, such as in patients with end-stage renal disease. Also used as a pharmaceutical buffering agent.
calcium carbonate an insoluble salt occurring naturally in bone, shells, and chalk; used as an antacid, calcium supplement, and phosphate binder, and for treatment of osteoporosis.
calcium channel blocker (calcium channel blocking agent) a drug such as nifedipine, diltiazem, or verapamil that selectively blocks the influx of calcium ions through a calcium channel of cardiac muscle and smooth muscle cells; used in the treatment of Prinzmetal's angina, chronic stable angina, and cardiac arrhythmias. Calcium channel blocking agents act to control arrhythmias by slowing the rate of sinoatrial node discharge and the conduction velocity through the atrioventricular node. They act in vasospastic angina to relax and prevent coronary artery spasm. The mechanism of action in classical angina is a lowering of myocardial oxygen utilization by dilating peripheral arteries and thereby reducing total peripheral resistance and the work of the heart.
 Physiologic activity of calcium channel blockers. (Data from Hardman J. and Limbird L., editors: Goodman and Gilman's The Pharmacologic Basis of Therapeutics, 9th ed., New York, McGraw-Hill, 1996; and the National Institutes of Health: The Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure, NIH Pub. No. 98-4080, Washington, DC, GPO, 1998.) From Edmunds and Mayhew, 2000.
calcium chloride a salt used in solution to restore electrolyte balance, treat hypocalcemia, and act as a treatment adjunct in cardiac arrest and in magnesium poisoning.
calcium citrate a salt used as a calcium replenisher; also used in the treatment of hyperphosphatemia in renal osteodystrophy.
calcium glubionate a calcium replenisher, used as a nutritional supplement and for the treatment of hypocalcemia; administered orally.
calcium gluceptate a calcium salt administered intramuscularly or intravenously in the prevention and treatment of hypocalcemia and as an electrolyte replenisher.
calcium gluconate a calcium salt administered intravenously or orally in the treatment and prevention of hypercalcemia and as a nutritional supplement. It is also administered by injection as a treatment adjunct in cardiac arrest and in the treatment of hyperkalemia.
calcium hydroxide an astringent compound used topically in solution or lotions.
calcium lactate a calcium replenisher, administered orally in the treatment and prevention of hypocalcemia and as a nutritional supplement.
calcium oxalate a salt of oxalic acid, which in excess in the urine may lead to formation of oxalate urinary calculi.
calcium oxide lime (def. 1).
calcium pantothenate a calcium salt of the dextrorotatory isomer of the B vitamin pantothenic acid; used as a nutritional supplement. It is also available as racemic calcium pantothenate, which is a mixture of the dextrorotatory and levorotatory isomeric forms.
calcium phosphate a salt containing calcium and the phosphate radical; dibasic and tribasic calcium phosphate are used as sources of calcium.
calcium polycarbophil a hydrophilic agent used as a bulk laxative.
calcium propionate a salt used as an antifungal preservative in foods and as a topical antifungal agent.
calcium pyrophosphate the pyrophosphate salt of calcium, used as a polishing agent in dentifrices. Crystals of the dihydrate form occur in the joints in calcium pyrophosphate deposition disease.
calcium pyrophosphate deposition disease an acute or chronic inflammatory arthropathy caused by deposition of crystals of calcium pyrophosphate dihydrate in the joints and synovial fluid and chondrocalcinosis. Clinically, it may resemble numerous other connective tissue diseases such as arthritis and gout, or it may be asymptomatic. Acute attacks are sometimes called pseudogout.
calcium sulfate a compound of calcium and sulfate, occurring as gypsum or as plaster of paris.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

cal·ci·um (Ca),

, gen.


(kal'sē-ŭm, -sē-ī),
A metallic bivalent element; atomic no. 20, atomic wt. 40.078, density 1.55, melting point 842°C. The oxide of calcium is an alkaline earth, CaO, quicklime, which on the addition of water becomes calcium hydrate, Ca(OH)2, slaked lime. For some organic calcium salts not listed below, see the name of the organic acid portion. Many calcium salts have crucial uses in metabolism and in medicine. Calcium salts are responsible for the radiopacity of bone, calcified cartilage, and arteriosclerotic plaques in arteries.
[Mod. L. fr. L. calx, lime]
Farlex Partner Medical Dictionary © Farlex 2012


A bivalent metallic element (atomic number 20; atomic weight 40.08) that is critical for bone and tooth formation and intimately linked to many metabolic processes, including muscle contraction, neural transmission, coagulation and inhibition of cell destruction. Calcium levels in the blood are controlled by the balanced action of parathyroid hormone and calcitonin. It is present in dairy products, almonds, leafy greens, sardines and salmon; proper absorption of calcium hinges on appropriate acidity of the stomach, presence of vitamin D and a balance of other minerals, including phosphorus and mangesium.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


A metal, atomic number 20, atomic weight 40.08, which is a divalent cation abundant in the body, especially in bone and teeth Calcium metabolism Ca2+ is the most critical mineral in bone–added by osteoblasts; removed by osteoclasts, Ca2+ maintains metabolic processes–eg, muscle contraction, neural transmission, cardiac activity, coagulation and inhibition of cell destruction; serum Ca2+ levels are controlled by a balance between PTH and calcitonin–produced by the thyroid's C or parafollicular cells; proper absorption of Ca2+ hinges on appropriate gastric acidity, presence of vitamin D, and a balance of other minerals–eg, phosphorus and mangesium; PTH ↑ serum Ca2+ levels by ↑ bone resorption via osteoclasts and mobilizing Ca2+, and indirectly ↑ GI absorption of Ca2+ by ↑ vitamin D production; PTH also ↑ phosphate excretion in the urine; calcitonin ↓ serum Ca2+ and phosphate levels by inhibiting bone resorption Daily requirement ± 400–1000 mg/day Ref range Infant to 1 month: 7.0-11.5 mg/dL; 1 month to 1 yr: 8.6-11.2 mg/dL >1 yr: 8.2-10.2 mg/dL; chronic abuse of laxatives, excess transfusions and various drugs can ↓ Ca2+ levels; Ca2+ is ↑ in hyperparathyroidism, parathyroid tumors, Paget's disease, myeloma, metastatic CA, multiple Fx, prolonged immobilization, renal disease, adrenal insufficiency, ↑ Ca2+ ingestion, antacid abuse; Ca2+ is ↓ in Cushing syndrome, hypoparathyroidism, malabsorption, acute pancreatitis, renal failure, peritonitis. See Hypercalcemia, Hypocalcemia, Ionized calcium.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


(Ca) (kal'sē-ŭm)
A metallic bivalent element; atomic no. 20, atomic wt. 40.078, density 1.55, melting point 842°C. Many calcium salts have crucial uses in metabolism and in medicine. Calcium salts are responsible for the radiopacity of bone, calcified cartilage, and arteriosclerotic plaques in arteries.
[Mod. L. fr. L. calx, lime]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


(kal'se-um) [ calci- + -ium] Ca
A silver-white metallic chemical element, atomic number 20, atomic weight (mass) 40.08. Lime (calcium oxide), CaO, is its oxide. Calcium is a major component of limestone. Hydroxylapatite, a calcium phosphate, makes up about 75% of body ash and about 85% of mineral matter in bones.


Calcium is important for blood clotting, enzyme activation, and acid-base balance. It gives firmness and rigidity to bones and teeth. It is essential for lactation, the function of nerves and muscles (including heart muscle), and maintenance of membrane permeability. Most absorption of calcium occurs in the duodenum and is dependent on the presence of calcitriol. Dietary factors affecting calcium absorption include phytic acid, consumption of too much phosphorus, and polyphenols found in tea. Approximately 40% of the calcium consumed is absorbed. Blood levels of calcium are regulated by parathyroid hormone; deficiency of this hormone produces hypocalcemia. The serum level of calcium is normally about 8.5 to 10.5 mg/dl. Low blood calcium causes tetany. Blood deprived of its calcium will not clot. Calcium is deposited in the bones but can be mobilized from them to keep the blood level constant when dietary intake is inadequate. At any given time, the body of an adult contains about 700 g of calcium phosphate; of this, 120 g is the element calcium. Adults should consume at least 1 g of calcium daily. Pregnant, lactating, and postmenopausal women should consume 1.2–1.5 g of calcium per day.


Excellent sources of calcium include milk and milk products (but not cottage cheese), and calcium-fortified orange juice. Good sources include canned salmon and sardines, broccoli, tofu, rhubarb, almonds, figs, and turnip greens.


1. Laboratory error and variation may sometimes cause inaccurate or inconsistent values in evaluating calcium levels.


2. Excessive calcium supplementation has been associated with a small increased risk of vascular calcification and heart attack.
CAS # 7440-70-2
See: hypercalcemia; hypocalcemia; osteoporosis


A radioactive isotope of calcium, half-life 164 days.

calcium chloride

CaCl2·2H2O, a salt used to raise the calcium content of the blood in disorders such as hypocalcemic tetany or overdose of calcium channel blocker or beta blocker. It is used in solution and administered intravenously. It is incompatible with epinephrine.
CAS # 10043-52-4

calcium cyclamate

C6H12NNaO3S, an artificial sweetening agent.
See: cyclamate

calcium disodium edetate

A substance used to bind metallic ions, such as lead or zinc. It is used to treat poisoning caused by those metals.

calcium gluconate

C12H22CaO14, a granular, white, odorless, and flavorless powder used to treat hypocalcemia, or overdose by calcium channel blocker or by beta blocker.
CAS # 299-28-5

calcium glycerophosphate

C3H7CaO6P, the calcium salt of glycerophosphoric acid. It is used as a dietary supplement, in drug formulation, and to prevent dental caries.
CAS # 27214-00-2

calcium hydroxide

Ca(OH)2, a white powder used as an astringent applied to the skin and mucous membranes and in dentistry as cavity liner or a pulp-capping material under a layer of zinc phosphate. It induces tertiary dentin formation for bridging or root closure, but it may be related to a chronic pulpitis and pulp necrosis after pulp capping.
CAS # 1305-62-0
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calcium oxalate

CaC2O4, a compound containing calcium, present in urine in crystalline form. It is a constituent of some kidney stones. See: illustration
CAS # 25454-23-3

calcium pantothenate

A salt of pantothenic acid, commonly used in vitamin supplements. Biochemically, it transfers acetyl groups from one compound to another. Egg yolks, liver, and yeasts are nutritional sources.

calcium saccharin

An artificial sweetening agent.
See: saccharin

total serum calcium

The sum of the soluble and protein-bound calcium in the blood.

calcium tungstate

CaWO4, a fluorescent material formerly used for radiologic imaging. It was used in intensifying screens to amplify the image, thereby reducing the radiation exposure to the patient.
Medical Dictionary, © 2009 Farlex and Partners


A mineral present in large quantity in the body, mainly in the form of calcium phosphate in the bones and the teeth. Electrically charged calcium atoms (ions) are present in the blood and body fluids and are essential for many physiological processes including cell membrane permeability, cell excitability, the initiation and transmission of electrical impulses, muscle contraction, cell shape and cell motility. Calcium is necessary for blood coagulation, the production of ATP, and enzyme actions. Calcium levels in the blood are kept withing narrow limits by feedback mechanisms. Brand names of preparations containing calcium used to treat OSTEOPOROSIS are Ostram and Sandocal.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

calcium (Ca)

an essential element to all animals and plants and a constituent of shells, bones and teeth.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005


A silvery-yellow metal that is the basic element of lime and makes up about 3% of the earth's crust. It is the most abundant mineral in the human body. Calcium and phosphorous combine as calcium phosphate, the hard material of bones and teeth.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


(Ca) (kal'sē-ŭm)
A metallic bivalent element; salts useful in metabolism and in medicine; responsible for radiopacity of bone, calcified cartilage, and arteriosclerotic arterial plaques in arteries.
[Mod. L. fr. L. calx, lime]
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about calcium

Q. It will be fine for my dad to take calcium as extra supplement; It will be fine for my dad to take calcium as extra supplement; as his bones are getting weak…. How much calcium intake is necessary for him?

A. Older men need more calcium, because, as they age, the body becomes less efficient at absorbing calcium and other nutrients. Intake amount can’t be judged without age and weight and other body conditions are known. Please don’t give supplements without doctor’s prescription as the chances of overdose are more problematic.

Q. My sister has been having major allergy problems.How could she get her desired calcium? My sister has been having major allergy problems. Now she has developed an allergy and cannot tolerate milk in any form. None of our family members had allergic reactions to milk and my sister very recently developed this symptom. Is there any possibility of this symptom linked with any other illness? How could she get her desired calcium intake required by the body? Can you make any suggestions please?

A. calcium is a very important part of our diet. lack of it will have a damaging effect. so it's good that you are aware!
many good sources of calcium exist. These include seaweeds such as kelp, wakame . nuts and seeds (like almonds and sesame). blackstrap molasses, beans, oranges, figs, quinoa , broccoli...
and another thing that you may do is crush an egg shell into powder and just mix a bit with her food. it's an excellent source.

Q. I'm concerned that my calcium supplements are contaminated w seashells or cow bones. Which brands are best

A. there should be labeled as "from animal source".
here is something that helped me choose:

More discussions about calcium
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