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Calcium Citrate

Medically reviewed by Last updated on Feb 6, 2019.


See also: Prolia

(KAL see um SIT rate)

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Capsule, Oral [preservative free]:

Cal-Citrate: 150 mg [dye free]

Granules, Oral:

Generic: 760 mg/3.5 g (480 g)

Tablet, Oral:

Generic: 250 mg, 1040 mg

Tablet, Oral [preservative free]:

Calcitrate: 950 mg [lactose free, milk derivatives/products, no artificial color(s), no artificial flavor(s), sodium free, soy free, sugar free, wheat free, yeast free]

Generic: 200 mg

Brand Names: U.S.

  • Cal-Citrate [OTC]
  • Calcitrate [OTC]

Pharmacologic Category

  • Calcium Salt


Moderates nerve and muscle performance via action potential excitation threshold regulation


25% to 35%, requires vitamin D; varies with age (infants 60%, prepubertal children 28%, pubertal children 34%, young adults 25%); decreased absorption occurs in patients with achlorhydria, renal osteodystrophy, steatorrhea, or uremia


Primarily in the feces as unabsorbed calcium

Protein Binding


Use: Labeled Indications

Calcium supplementation: Use as a dietary supplement when calcium intake may be inadequate (eg, osteoporosis, osteomalacia, hypocalcemic rickets) (IOM 2011)

Off Label Uses

Hypoparathyroidism (management of chronic hypocalcemia)

Based on guidelines from the Endocrine Society and the European Society of Endocrinology for the management of hypoparathyroidism, supplemental calcium (in conjunction with vitamin D) is effective and recommended in the management of chronic hypocalcemia associated with hypoparathyroidism [Endocrine Society [Brandi 2016]], [European Society of Endocrinology [Bollerslev 2015]]. Calcium citrate is recommended (over other oral calcium preparations) for patients with achlorhydria or who are on chronic proton pump inhibitor therapy [European Society of Endocrinology [Bollerslev 2015]].

Dosing: Adult

Hypoparathyroidism (management of chronic hypocalcemia) (off-label use): Oral: 500 mg to 1 g of elemental calcium administered 2 to 3 times daily; required dose can vary greatly and more frequent dosing may be necessary. Note: Use of IV calcium may be required in acute hypocalcemia with corrected calcium <7 mg/dL (≤1.75 mmol/L) or in severely symptomatic patients (eg, arrhythmias, broncho- or laryngospasm, tetany, seizures) (Bilezikian 2016).

Calcium supplementation (OTC labeling): Oral: 200 mg to 1 g/day (as elemental calcium) as a single dose or in divided doses. Note: The recommended daily intake of elemental calcium (from dietary sources and supplemental sources if needed) for optimal bone health is 1.2 g/day (postmenopausal women) or 1 to 1.2 g/day in other adults. It is preferred to obtain these daily amounts primarily through dietary sources. There is no evidence that intakes higher than these improve bone strength (AACE [Camacho 2016]; Endocrine Society [Watts 2012]; IOM 2011; NOF [Cosman 2014]).

Dosing: Pediatric

Note: Calcium citrate 1,000 mg = 211 mg elemental calcium = 10.5 mEq calcium

Adequate intake (AI) (IOM 2011): Dosage expressed in terms of elemental calcium: Oral:

1 to 6 months: 200 mg/day

7 to 12 months: 260 mg/day

Recommended daily allowance (RDA) (IOM 2011): Dosage expressed in terms of elemental calcium: Oral:

1 to 3 years: 700 mg/day

4 to 8 years: 1,000 mg/day

9 to 18 years: 1,300 mg/day

Hypocalcemia: Dose depends on clinical condition and serum calcium concentration: Dose expressed as elemental calcium: Limited data available: Infants and Children: Oral: 45 to 65 mg/kg/day in 4 divided doses (Nelson 1996)


May administer with or without food; administration with food may increase absorption. Doses >600 mg (elemental calcium) per day should be divided for optimal absorption (AACE [Camacho 2016]).

Dietary Considerations

Dietary reference intake for calcium (IOM 2011):

0 to <6 months: Adequate intake: 200 mg elemental calcium daily

6 to 12 months: Adequate intake: 260 mg elemental calcium daily

1 to 3 years: RDA: 700 mg elemental calcium daily

4 to 8 years: RDA: 1,000 mg elemental calcium daily

9 to 18 years: RDA: 1,300 mg elemental calcium daily

19 to 50 years: RDA: 1,000 mg elemental calcium daily

Females ≥51 years: RDA: 1,200 mg elemental calcium daily

Males: 51 to 70 years: RDA: 1,000 mg elemental calcium daily; >70 years: RDA: 1,200 mg elemental calcium daily

Pregnancy/Lactating: RDA: Requirements are the same as in nonpregnant or nonlactating females


Store at room temperature.

Drug Interactions

Alpha-Lipoic Acid: Calcium Salts may decrease the absorption of Alpha-Lipoic Acid. Alpha-Lipoic Acid may decrease the absorption of Calcium Salts. Consider therapy modification

Aluminum Hydroxide: Citric Acid Derivatives may increase the absorption of Aluminum Hydroxide. Monitor therapy

Baloxavir Marboxil: Polyvalent Cation Containing Products may decrease the serum concentration of Baloxavir Marboxil. Avoid combination

Bictegravir: Calcium Salts may decrease the serum concentration of Bictegravir. Management: Bictegravir, emtricitabine, and tenofovir alafenamide can be administered with calcium salts under fed conditions, but coadministration with or 2 hours after a caclium salt is not recommended under fasting conditions. Consider therapy modification

Bisphosphonate Derivatives: Polyvalent Cation Containing Products may decrease the serum concentration of Bisphosphonate Derivatives. Management: Avoid administration of oral medications containing polyvalent cations within: 2 hours before or after tiludronate/clodronate/etidronate; 60 minutes after oral ibandronate; or 30 minutes after alendronate/risedronate. Exceptions: Pamidronate; Zoledronic Acid. Consider therapy modification

Calcium Acetate: Calcium Salts may enhance the adverse/toxic effect of Calcium Acetate. Avoid combination

Calcium Channel Blockers: Calcium Salts may diminish the therapeutic effect of Calcium Channel Blockers. Monitor therapy

Cardiac Glycosides: Calcium Salts may enhance the arrhythmogenic effect of Cardiac Glycosides. Monitor therapy

Deferiprone: Polyvalent Cation Containing Products may decrease the serum concentration of Deferiprone. Management: Separate administration of deferiprone and oral medications or supplements that contain polyvalent cations by at least 4 hours. Consider therapy modification

DOBUTamine: Calcium Salts may diminish the therapeutic effect of DOBUTamine. Monitor therapy

Dolutegravir: Calcium Salts may decrease the serum concentration of Dolutegravir. Management: Administer dolutegravir at least 2 hours before or 6 hours after oral calcium. Administer dolutegravir/rilpivirine at least 4 hours before or 6 hours after oral calcium salts. Alternatively, dolutegravir and oral calcium can be taken together with food. Consider therapy modification

Eltrombopag: Polyvalent Cation Containing Products may decrease the serum concentration of Eltrombopag. Management: Administer eltrombopag at least 2 hours before or 4 hours after oral administration of any polyvalent cation containing product. Consider therapy modification

Estramustine: Calcium Salts may decrease the absorption of Estramustine. Consider therapy modification

Multivitamins/Fluoride (with ADE): May increase the serum concentration of Calcium Salts. Calcium Salts may decrease the serum concentration of Multivitamins/Fluoride (with ADE). More specifically, calcium salts may impair the absorption of fluoride. Management: Avoid eating or drinking dairy products or consuming vitamins or supplements with calcium salts one hour before or after of the administration of fluoride. Consider therapy modification

Multivitamins/Minerals (with ADEK, Folate, Iron): May increase the serum concentration of Calcium Salts. Monitor therapy

PenicillAMINE: Polyvalent Cation Containing Products may decrease the serum concentration of PenicillAMINE. Management: Separate the administration of penicillamine and oral polyvalent cation containing products by at least 1 hour. Consider therapy modification

Phosphate Supplements: Calcium Salts may decrease the absorption of Phosphate Supplements. Management: This applies only to oral phosphate and calcium administration. Administering oral phosphate supplements as far apart from the administration of an oral calcium salt as possible may be able to minimize the significance of the interaction. Exceptions: Sodium Glycerophosphate Pentahydrate. Consider therapy modification

Quinolones: Calcium Salts may decrease the absorption of Quinolones. Of concern only with oral administration of both agents. Exceptions: LevoFLOXacin (Oral Inhalation); Moxifloxacin (Systemic). Consider therapy modification

Strontium Ranelate: Calcium Salts may decrease the serum concentration of Strontium Ranelate. Management: Separate administration of strontium ranelate and oral calcium salts by at least 2 hours in order to minimize this interaction. Consider therapy modification

Tetracyclines: Calcium Salts may decrease the serum concentration of Tetracyclines. Management: If coadministration of oral calcium with oral tetracyclines can not be avoided, consider separating administration of each agent by several hours. Exceptions: Eravacycline. Consider therapy modification

Thiazide and Thiazide-Like Diuretics: May decrease the excretion of Calcium Salts. Continued concomitant use can also result in metabolic alkalosis. Monitor therapy

Thyroid Products: Calcium Salts may diminish the therapeutic effect of Thyroid Products. Management: Separate the doses of the thyroid product and the oral calcium supplement by at least 4 hours. Consider therapy modification

Trientine: Polyvalent Cation Containing Products may decrease the serum concentration of Trientine. Management: Avoid concomitant administration of trientine and oral products that contain polyvalent cations. If oral iron supplements are required, separate the administration by 2 hours. If other oral polyvalent cations are needed, separate administration by 1 hour. Consider therapy modification

Vitamin D Analogs: Calcium Salts may enhance the adverse/toxic effect of Vitamin D Analogs. Monitor therapy

Adverse Reactions

Frequency not defined. Mild hypercalcemia (calcium: >10.5 mg/dL) may be asymptomatic or manifest as anorexia, constipation, nausea, and vomiting. More severe hypercalcemia (calcium: >12 mg/dL) is associated with coma, confusion, delirium, and stupor.

Central nervous system: Headache

Endocrine & metabolic: Hypercalcemia, hypophosphatemia, increased thirst

Gastrointestinal: Abdominal pain, anorexia, constipation, nausea, vomiting


Concerns related to adverse effects:

• Gastrointestinal effects: Constipation, bloating, and gas are common with calcium supplements (especially carbonate salt).

• Hypercalcemia: Chronic hypercalcemia may result in generalized vascular and soft tissue calcification, exacerbate nephrolithiasis, and has been associated with increased mortality in adults with chronic kidney disease (CKD) (KDIGO 2017).

Disease-related concerns:

• Achlorhydria: Calcium absorption is impaired in achlorhydria; common in elderly. Citrate may be preferred because better absorbed.

• Hypoparathyroid disease: Hypercalcemia and hypercalciuria are most likely to occur in hypoparathyroid patients receiving high doses of vitamin D.

• Kidney stones (calcium-containing): Use caution when administering calcium supplements to patients with a history of kidney stones.

• Renal impairment: Use with caution in patients with renal failure to avoid hypercalcemia; frequent monitoring of serum calcium and phosphorus is necessary.

Concurrent drug therapy issues:

• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

Other warnings/precautions:

• Absorption: Taking calcium (≤500 mg) with food improves absorption.

• Appropriate product selection: Multiple salt forms of calcium exist; close attention must be paid to the salt form when ordering and administering calcium; incorrect selection or substitution of one salt for another without proper dosage adjustment may result in serious over or under dosing.

Monitoring Parameters

Monitor plasma calcium levels if using calcium salts as electrolyte supplements for deficiency.

Calcium supplementation in hypoparathyroidism (Endocrine Society [Brandi 2016]): Note: Frequency of measurement is dependent upon on how stable a patient is to a given dosage regimen with more frequent measurements (eg, weekly) required initially during dosage titration. Once patient is well controlled, monitoring may be required on a yearly or twice-yearly basis.

Serum calcium, phosphate, and magnesium; renal function (ie, 24-hour urinary calcium and creatinine, blood urea nitrogen [BUN]), measured CrCl or estimated glomerular filtration rate (eGFR); renal imaging (every 5 years in asymptomatic patients with a history of renal lithiasis or calcinosis or more frequently as indicated); CNS imaging (basal ganglia and other sites of calcification), ophthalmologic exam, and/or BMD as clinically indicated

Pregnancy Considerations

Calcium crosses the placenta. Intestinal absorption of calcium increases during pregnancy. The amount of calcium reaching the fetus is determined by maternal physiological changes. Calcium requirements are the same in pregnant and nonpregnant females (IOM, 2011).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience constipation, nausea, vomiting, abdominal pain, or lack of appetite. Have patient report immediately to prescriber mood changes or signs of high calcium (weakness, confusion, fatigue, headache, nausea and vomiting, constipation, or bone pain) (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

Further information

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