Mineral supplements. Calcium
ATC code: A12AA04 (Calcium carbonate)
Brand names
Tums, Caltrate, Os-Cal, Rolaids
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.
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.
Adjunct
Calcium carbonate combined with vitamin D is a mandatory background component of postmenopausal osteoporosis therapy. The standard dose is 1000–1200 mg elemental calcium daily plus 800–1000 IU vitamin D3. Dietary calcium intake is considered, and the dose is adjusted so total intake does not exceed 1500 mg/day. Calcium monotherapy without disease-modifying therapy (bisphosphonates, denosumab, romosozumab) does not prevent fractures in confirmed osteoporosis.
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.
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.
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.
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.
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.
1 pair found. Sorted from critical to minor.
Mechanism
Кальций связывает левотироксин в просвете и снижает его абсорбцию на 20–25%.
Management
Разнести прием минимум на 4 часа. Левотироксин утром натощак, кальций – через 4 часа или вечером.
No FDA category assigned. Use during pregnancy is acceptable at doses not exceeding physiological needs (1000 mg elemental calcium daily total intake). High doses are not used – risk of maternal hypercalciuria and placental calcification.
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 evaluated for the following indications with varying evidence strength: Postmenopausal osteoporosis (evidence tier A), Mild hypocalcemia (evidence tier A), Antacid therapy for mild dyspepsia (evidence tier B). 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.
No FDA category assigned. Use during pregnancy is acceptable at doses not exceeding physiological needs (1000 mg elemental calcium daily total intake). High doses are not used – risk of maternal hypercalciuria and placental calcification.
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.