Calcium (oral salts: carbonate, citrate, lactate, gluconate)

Mineral supplements. Calcium

ATC code: A12AA-CALCIUM (Calcium (oral salts, generic group))

Brand names – drugs

Caltrate

Brand names – supplements

Citracal, NOW Foods Calcium Citrate

Supplements are not tested in clinical trials and are not registered as medications.

Mechanism of action

Calcium is the main structural component of bone tissue (99% of total body calcium). A cofactor for blood coagulation cascades, neuromuscular transmission, and secretory processes. Maintains cell membrane resting potential. Absorbed in the small intestine via calcium-binding protein whose synthesis is regulated by calcitriol. Bioavailability depends on the salt form and gastric pH: citrate is absorbed independent of pH; carbonate requires an acidic environment and is taken with food.

Indications

Hypocalcaemia

First line

Oral calcium is first-line for mild-to-moderate hypocalcaemia. Treatment dose: 1,000–2,000 mg elemental calcium daily in 2–3 portions with concurrent vitamin D correction and elimination of the cause. In severe symptomatic hypocalcaemia (tetany, laryngospasm, QT prolongation), intravenous calcium gluconate is used.

Sources

Postmenopausal osteoporosis

First line

First-line and a required component of combined postmenopausal osteoporosis therapy, always with vitamin D 800–1,000 IU and antiresorptive or anabolic agents. Endocrine Society 2019 and 2018 recommend 1,000–1,200 mg elemental calcium daily (including dietary intake) in postmenopausal women with osteoporosis or high fracture risk. Calcium monotherapy without vitamin D and without primary antiosteoporotic therapy does not reduce fracture incidence.

Consider total calcium intake (diet + supplementation). Doses above 2,000 mg daily as supplements increase vascular calcification risk without sound clinical justification.

Sources

Pre-eclampsia prevention in low dietary calcium intake

Individual decision

In pregnant women with low dietary calcium intake (less than 600 mg daily), supplementation of 1.5–2 g elemental calcium daily reduces pre-eclampsia risk by about 50% per the 2015 Cochrane meta-analysis. 2020 recommends this intervention in populations with low baseline intake. In women with adequate dietary calcium, the effect is minimal.

The Russian population generally has adequate calcium intake on a varied diet. Supplementation decisions are individualised after dietary review.

Sources

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Primary cardiovascular prevention in individuals without established CVD

Not recommended

Isolated supplemental calcium (above 1,000 mg daily) in adults without osteoporosis for cardiovascular risk reduction is not indicated. The 2010 BMJ meta-analysis (Bolland et al.) found a 24 % increase in myocardial infarction risk with isolated high-dose calcium. Subsequent data are mixed, but cardiology societies do not recommend isolated calcium as cardiovascular prevention. Standard prevention: blood pressure control, statins when clinically indicated, smoking cessation.

Sources

Endocrine Society: Postmenopausal Osteoporosis Treatment Guidelines (2019)

Practical notes

Timing and administration

Calcium carbonate is taken with meals – an acidic gastric environment is needed for dissolution. Calcium citrate is absorbed independently of gastric pH – suitable for patients on proton pump inhibitors and older adults with hypoacid gastritis; can be taken on an empty stomach. Single dose ideally not more than 500–600 mg elemental calcium – larger doses are absorbed less efficiently. Distribute over 2–3 daily intakes.

Dose titration

Daily allowance for adults: 1,000 mg (1,200 mg for women after 50 and men after 70). In osteoporosis with dietary intake considered: 1,000–1,200 mg total daily. In pregnancy with low intake: 1,500–2,000 mg daily. Upper tolerable intake level (UL): 2,500 mg daily.

Monitoring

No specific monitoring at physiological doses. With long-term high doses (above 1,500 mg daily) in renal impairment, monitor serum calcium and creatinine; in patients with urolithiasis, monitor 24-hour urine calcium. In older adults, periodically assess renal function.

Food and drinks

Dietary sources: dairy (milk 250 mL – 300 mg, hard cheese 30 g – 200 mg, yoghurt 200 g – 250 mg), fish with bones (sardines, sprats), broccoli, almonds, sesame, calcium-fortified foods. Most adults in Russia with dairy in their diet meet the RDA without supplements. Calcium with meals competes with iron and zinc absorption – separate by 2 hours.

Common myths

Myth: “everyone over 40 needs calcium for strong bones”. Fact: with adequate dietary intake, supplemental calcium does not reduce fracture risk in people without osteoporosis. Isolated supplementation without vitamin D and physical activity has minimal effect on bone density.

Myth: “calcium deposits in vessels – harmful”. Fact: there are data on increased cardiovascular risk with high-dose calcium (above 1,000 mg daily isolated, without vitamin D), but with standard combined osteoporosis therapy with vitamin D the effect is minimised. The best approach is dietary calcium, not supplements.

Myth: “calcium gluconate is the best”. Fact: gluconate contains little elemental calcium (9%) – 12–15 tablets are needed for a treatment dose. Carbonate contains 40% elemental calcium, citrate 21%. Carbonate is the most cost-effective form with preserved gastric acidity; citrate is for hypoacidity.

Drug–nutrient interactions

Iron

Calcium above 300 mg reduces iron absorption by 40–60%. Separate iron and calcium intake by at least 2 hours.

Vitamin D

Vitamin D enhances intestinal calcium absorption by stimulating calcium-binding protein synthesis. In osteoporosis treatment, calcium is prescribed only with vitamin D – monotherapy is ineffective.

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Official sources

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GRLS

Russian State Register of Medicines

Safety

Contraindications

Hypercalcaemia of any aetiology
Severe hypercalciuria
Calcium-containing kidney stones
Severe renal impairment
Sarcoidosis and other granulomatous diseases (relative)
Hypersensitivity to components

Serious adverse effects

Hypercalcaemia with high doses in renal impairment or granulomatous diseases
Milk-alkali syndrome with high-dose calcium carbonate combined with alkaline antacids
Kidney stone formation with long-term high-dose therapy without adequate hydration

Common adverse effects

Constipation
Flatulence, eructation
Nausea at larger doses

Uncommon adverse effects

Hypercalciuria
Allergic reactions

PregnancyFDA C

Safe at physiological doses. Supplementation at 1,000–1,200 mg daily during pregnancy and lactation is encouraged by international obstetric societies. In pregnant women with low dietary intake: 1,500–2,000 mg daily.

Breastfeeding

Calcium is actively secreted into breast milk. Lactating women are advised to take 1,000–1,200 mg elemental calcium daily including dietary intake.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Calcium (oral salts: carbonate, citrate, lactate, gluconate) used for?

Calcium (oral salts: carbonate, citrate, lactate, gluconate) is evaluated for the following indications with varying evidence strength: Hypocalcaemia (evidence tier A), Postmenopausal osteoporosis (evidence tier A), Pre-eclampsia prevention in low dietary calcium intake (evidence tier B). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Calcium (oral salts: carbonate, citrate, lactate, gluconate)?

Common side effects of Calcium (oral salts: carbonate, citrate, lactate, gluconate) (≥ 1 in 100): Constipation, Flatulence, eructation, Nausea at larger doses. See the Safety section for uncommon and serious reactions.

Is Calcium (oral salts: carbonate, citrate, lactate, gluconate) safe during pregnancy?

FDA category C. Safe at physiological doses. Supplementation at 1,000–1,200 mg daily during pregnancy and lactation is encouraged by international obstetric societies. In pregnant women with low dietary intake: 1,500–2,000 mg daily.

Is Calcium (oral salts: carbonate, citrate, lactate, gluconate) compatible with breastfeeding?

Calcium is actively secreted into breast milk. Lactating women are advised to take 1,000–1,200 mg elemental calcium daily including dietary intake.

Who should not take Calcium (oral salts: carbonate, citrate, lactate, gluconate)?

Calcium (oral salts: carbonate, citrate, lactate, gluconate) is contraindicated in: Hypercalcaemia of any aetiology; Severe hypercalciuria; Calcium-containing kidney stones; Severe renal impairment; Sarcoidosis and other granulomatous diseases (relative). Full list in the Safety section.

“everyone over 40 needs calcium for strong bones”

with adequate dietary intake, supplemental calcium does not reduce fracture risk in people without osteoporosis. Isolated supplementation without vitamin D and physical activity has minimal effect on bone density.

“calcium deposits in vessels – harmful”

there are data on increased cardiovascular risk with high-dose calcium (above 1,000 mg daily isolated, without vitamin D), but with standard combined osteoporosis therapy with vitamin D the effect is minimised. The best approach is dietary calcium, not supplements.

“calcium gluconate is the best”

gluconate contains little elemental calcium (9%) – 12–15 tablets are needed for a treatment dose. Carbonate contains 40% elemental calcium, citrate 21%. Carbonate is the most cost-effective form with preserved gastric acidity; citrate is for hypoacidity.

Mechanism of action

Indications

Hypocalcaemia

First line

Sources

Postmenopausal osteoporosis

First line

Consider total calcium intake (diet + supplementation). Doses above 2,000 mg daily as supplements increase vascular calcification risk without sound clinical justification.

Sources

Pre-eclampsia prevention in low dietary calcium intake

Individual decision

The Russian population generally has adequate calcium intake on a varied diet. Supplementation decisions are individualised after dietary review.

Sources

Practical notes

Timing and administration

Dose titration

Monitoring

Food and drinks

Common myths

Drug–nutrient interactions

Iron

Calcium above 300 mg reduces iron absorption by 40–60%. Separate iron and calcium intake by at least 2 hours.

Vitamin D

Vitamin D enhances intestinal calcium absorption by stimulating calcium-binding protein synthesis. In osteoporosis treatment, calcium is prescribed only with vitamin D – monotherapy is ineffective.

Safety

Contraindications

Hypercalcaemia of any aetiology
Severe hypercalciuria
Calcium-containing kidney stones
Severe renal impairment
Sarcoidosis and other granulomatous diseases (relative)
Hypersensitivity to components

Serious adverse effects

Hypercalcaemia with high doses in renal impairment or granulomatous diseases
Milk-alkali syndrome with high-dose calcium carbonate combined with alkaline antacids
Kidney stone formation with long-term high-dose therapy without adequate hydration

Common adverse effects

Constipation
Flatulence, eructation
Nausea at larger doses

Uncommon adverse effects

Hypercalciuria
Allergic reactions

PregnancyFDA C

Breastfeeding

Calcium is actively secreted into breast milk. Lactating women are advised to take 1,000–1,200 mg elemental calcium daily including dietary intake.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Calcium (oral salts: carbonate, citrate, lactate, gluconate) used for?

What are the side effects of Calcium (oral salts: carbonate, citrate, lactate, gluconate)?

Is Calcium (oral salts: carbonate, citrate, lactate, gluconate) safe during pregnancy?

Is Calcium (oral salts: carbonate, citrate, lactate, gluconate) compatible with breastfeeding?

Calcium is actively secreted into breast milk. Lactating women are advised to take 1,000–1,200 mg elemental calcium daily including dietary intake.

Who should not take Calcium (oral salts: carbonate, citrate, lactate, gluconate)?

“everyone over 40 needs calcium for strong bones”

“calcium deposits in vessels – harmful”

“calcium gluconate is the best”