Mineral supplements. Calcium
Brand names: Tums, Caltrate, Os-Cal, Rolaids
Updated · Methodology
First line
In mild asymptomatic hypocalcemia (total calcium 2.0–2.2 mmol/L), oral calcium at 1000–1500 mg elemental calcium daily plus vitamin D usually normalizes the level. Calcium is rechecked at 1–2 weeks. If hypocalcemia persists, magnesium, PTH, vitamin D and eGFR are evaluated.
Sources
ICD-10: E83.5 · ICD-11: 5C64.5
Second line
For occasional heartburn and acid regurgitation, calcium carbonate as an antacid rapidly neutralizes acid and relieves symptoms. The effect is short-lived (30–60 minutes). Symptoms more than twice a week require workup (GERD, H. pylori, functional dyspepsia) and consideration of a PPI. Antacid use beyond 2 weeks without effect is reassessed.
ICD-10: K30 · ICD-11: DD90.3
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
Not recommended
Calcium supplementation alone, without vitamin D and disease-modifying therapy, does not reduce fracture risk in most patients with confirmed osteoporosis. International guidelines treat calcium only as a background component combined with vitamin D and mandatory disease-modifying therapy (bisphosphonates, denosumab, romosozumab). «Calcium for bones» without full assessment and disease-modifying therapy is marketing positioning.
ICD-10: M81.9 · ICD-11: FB83.1
Not recommended
Calcium supplementation for primary cardiovascular prevention is not indicated. The 2018 concluded that in asymptomatic postmenopausal women, additional calcium and vitamin D supplementation provides no advantage over a balanced diet for fracture and CVD prevention. The 2010–2013 meta-analyses (Bolland et al.) suggested a possible increase in MI risk with isolated calcium, although subsequent larger analyses have not confirmed the effect.
A source of elemental calcium, providing 40% by mass. In the stomach it dissociates into calcium and bicarbonate ions. Calcium is absorbed in the small intestine by active vitamin D-dependent transport and passive diffusion. Bicarbonate neutralizes hydrochloric acid – hence the antacid effect. Bioavailability depends on gastric acidity: hypoacidity or PPI therapy reduces absorption, in which case organic calcium salts (citrate) are preferred.
AEMPS summary of product characteristics (section 4.6): calcium carbonate can be used during pregnancy. Daily calcium intake should not exceed 2,500 mg, because persistent hypercalcaemia has been linked to adverse effects on fetal development.
Calcium is an essential component of a lactating mother's diet. Calcium supplementation at physiological doses is safe and compatible with breastfeeding.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Calcium carbonate forms insoluble complexes with levothyroxine in the gut lumen and reduces its absorption. With concurrent dosing, the levothyroxine dose becomes insufficient, leading to hypothyroidism. A separation of at least 4 hours is maintained between fasting morning levothyroxine and calcium carbonate.
Calcium chelates with fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) and reduces their absorption by 30–50%. A separation of at least 2 hours before and 6 hours after a fluoroquinolone dose is maintained before calcium carbonate.
Calcium chelates oral bisphosphonates (alendronate, risedronate, ibandronate) and blocks their absorption completely. Bisphosphonates are taken strictly fasting 30–60 minutes before breakfast, no later than the first meal and no earlier than 30 minutes before calcium. Failure to observe the interval nullifies antiresorptive therapy.
Calcium competes with iron for absorption in the duodenum. In patients with iron-deficiency anemia, a 2-hour interval between calcium and iron supplements is maintained.
12 pairs found. Sorted from critical to minor.
Mechanism
Calcium carbonate may reduce bisoprolol GI absorption when taken simultaneously. The effect is weak and clinically minor.
Symptoms
Minimal changes. In some patients, mild return of hypertension or angina symptoms with prolonged concurrent use.
Management
Separate bisoprolol and calcium carbonate by 2 hours. Most patients require no special adjustment.
Mechanism
Calcium forms insoluble chelates with ciprofloxacin in the gut. Antibiotic bioavailability falls by 40–50%, raising the risk of clinical failure.
Symptoms
Persistent fever, infection symptoms, and inflammation markers 48–72 hours after antibiotic start.
Management
Take ciprofloxacin 2 hours before or 6 hours after calcium carbonate. Apply the same interval for iron, zinc, magnesium, and aluminium-containing antacids. If timing separation is impossible (e.g. continuous calcium need), choose an alternative antibiotic (amoxicillin-clavulanate, a cephalosporin).
Mechanism
Calcium binds levothyroxine in the gut as insoluble complexes, reducing absorption by 20–25%.
Symptoms
Return of hypothyroidism: fatigue, weight gain, cold intolerance, dry skin, low mood. In thyroid cancer, loss of TSH control.
Management
Take levothyroxine in the morning on empty stomach, 30–60 minutes before food and other drugs. Take calcium carbonate 4 hours after levothyroxine (e.g. at lunch or in the evening). Check TSH 6–8 weeks after starting calcium.
Mechanism
Antacids accelerate renal aspirin elimination via urinary alkalinisation. At cardioprotective doses (75–100 mg/day), the effect is clinically minimal.
Symptoms
The combination usually causes no specific symptoms. Each drug's individual side effects remain.
Management
At cardioprotective aspirin doses, no adjustment needed. At high anti-inflammatory doses (over 3 g/day) with simultaneous antacid for several days, efficacy may slightly drop — separate dosing by 2 hours.
Mechanism
No clinically significant direct interaction. Oral calcium does not affect amlodipine: vascular smooth muscle calcium channel blockade is intracellular and is not overcome by exogenous calcium.
Symptoms
The combination usually causes no specific symptoms. Each drug's individual side effects remain.
Management
No dose adjustment needed. In patients with hypertension and osteoporosis, the combination is standard.
Mechanism
Vitamin D increases intestinal calcium absorption by activating calbindin in enterocytes. The synergistic effect benefits osteoporosis and calcium deficiency.
Symptoms
On a balanced dose, no symptoms. At excessive doses of vitamin D (over 4000 IU/day chronically) and calcium (over 1500 mg/day), hypercalcaemia risk: thirst, polyuria, nausea, weakness, arrhythmia.
Management
Standard combination in osteoporosis prevention and treatment: colecalciferol 800–2000 IU/day plus calcium 1000–1200 mg/day (counting dietary calcium). Check calcium and creatinine every 6 months in patients with chronic kidney disease or prior nephrolithiasis.
Mechanism
Doxycycline forms non-absorbable chelates with calcium in the gut (and with other polyvalent cations — magnesium, iron, aluminium). Doxycycline bioavailability falls by 50–80%.
Symptoms
Persistent infection symptoms 48–72 hours after antibiotic start, risk of clinical failure.
Management
Take doxycycline 2 hours before or 6 hours after calcium carbonate. Apply the same interval for iron, magnesium, zinc, and aluminium-containing antacids. If timing separation is impossible, choose an alternative antibiotic (amoxicillin, a cephalosporin).
Sources
Mechanism
Calcium carbonate as an antacid mildly reduces lithium intestinal absorption, but no clinically significant drop in blood concentration has been documented.
Symptoms
The combination usually causes no specific symptoms. Each drug's individual side effects remain.
Management
No dose adjustment needed. Check lithium levels on the usual schedule (every 3 months on stable dose). With significant clinical changes (return of manic or depressive symptoms), check off-schedule.
Sources
Mechanism
Calcium carbonate slightly reduces metformin intestinal absorption when taken together. Clinically significant hyperglycaemia has not been described.
Symptoms
The combination usually causes no specific symptoms. Each drug's individual side effects remain.
Management
Take metformin with or just after meals; take calcium carbonate 2 hours after meals or in the evening. On the combination, monitor on the usual schedule. In diabetics with osteoporosis, the combination is standard.
Sources
Mechanism
Calcium carbonate as an antacid may theoretically reduce metronidazole absorption, but no clinically significant effect on antibacterial efficacy has been described.
Symptoms
The combination usually causes no specific symptoms. Each drug's individual side effects remain.
Management
For short metronidazole courses (5–10 days), no specific adjustment needed. In Helicobacter pylori eradication (with bismuth or a PPI), the combination is standard.
Mechanism
Calcium carbonate and sertraline are metabolised by different pathways. No direct interaction.
Symptoms
The combination usually causes no specific symptoms. Each drug's individual side effects remain.
Management
No dose adjustment needed. In women with depression and osteoporosis, the combination is standard.
Mechanism
Simethicone is a surface-active silicone agent that is not absorbed in the gastrointestinal tract. No direct pharmacokinetic interaction with calcium carbonate.
Symptoms
The combination usually causes no specific symptoms. Each drug's individual side effects remain.
Management
No dose adjustment needed. The combination is standard in symptomatic formulations for bloating and heartburn.
Sources
Verbatim lines from the interaction sections, in the language of the label
«Los corticosteroides sistémicos reducen la absorción de calcio. Durante su uso concomitante, puede ser necesario aumentar la dosis de Carbocal 600 mg comprimidos.»AEMPS, section 4.5 · Open on CIMA
«La hipercalcemia puede aumentar la toxicidad de los glucósidos cardiacos durante el tratamiento con calcio. Los pacientes deben controlarse mediante electrocardiograma (ECG) y niveles séricos de…»AEMPS, section 4.5 · Open on CIMA
«Los diuréticos tiazídicos reducen la excreción urinaria de calcio. Debido al aumento del riesgo de hipercalcemia, debe controlarse regularmente el calcio sérico durante el uso concomitante de…»AEMPS, section 4.5 · Open on CIMA
«Si se utiliza un bifosfonato o fluoruro de sodio de forma concomitante, esta preparación deberá administrarse al menos tres horas antes de la ingesta de Carbocal 600 mg comprimidos pues puede…»AEMPS, section 4.5 · Open on CIMA
«La absorción de quinolonas podría verse perjudicada si se administra concomitantemente con calcio. Las quinolonas se deben tomar 2 horas antes o 6 horas depués de la ingesta de calcio.»AEMPS, section 4.5 · Open on CIMA
«El carbonato cálcico puede interferir con la absorción de preparaciones de tetraciclinas administradas de forma concomitante. Por este motivo, las preparaciones de tetraciclinas deben administrarse…»AEMPS, section 4.5 · Open on CIMA
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Calcium carbonate is evaluated for the following indications with varying evidence strength: Mild hypocalcemia (evidence tier A), Antacid therapy for mild dyspepsia (evidence tier B), Calcium monotherapy for osteoporosis (evidence tier F). See the full indication matrix with dosing and citations above on this page.
Common side effects of Calcium carbonate (≥ 1 in 100): Constipation, Flatulence, belching, Nausea. See the Safety section for uncommon and serious reactions.
AEMPS summary of product characteristics (section 4.6): calcium carbonate can be used during pregnancy. Daily calcium intake should not exceed 2,500 mg, because persistent hypercalcaemia has been linked to adverse effects on fetal development.
Calcium is an essential component of a lactating mother's diet. Calcium supplementation at physiological doses is safe and compatible with breastfeeding.
Calcium carbonate is contraindicated in: Hypercalcemia of any cause; Hypercalciuria with stone disease risk; Active urolithiasis; Severe renal impairment (eGFR < 30 mL/min/1.73 m²); Sarcoidosis and other granulomatous diseases with hypercalcemia. Full list in the Safety section.
beyond 1500 mg daily, additional calcium offers no extra benefit and increases hypercalciuria and stone disease risk.
the 2018 USPSTF found no benefit of prophylactic supplementation in asymptomatic women. Adequate dietary intake is usually enough; supplements are indication-based after risk assessment.
confirmed osteoporosis requires disease-modifying therapy (bisphosphonates, denosumab, romosozumab). Calcium and vitamin D are background components.
Direct links to regulator labels. Open in a new tab.
Calcium + Cholecalciferol, Calcium D-glucarate, Chromium picolinate, Copper, Magnesium L-threonate (Magtein), Molybdenum, Selenium (oral salts and chelates: selenomethionine, sodium selenite, selenium yeast), Magnesium (oral salts: citrate, glycinate, oxide, sulfate)