Not scheduled (OTC)

Oral

• Tablets: 250 mg, 500 mg, 600 mg, 750 mg, 1000 mg (elemental calcium equivalents)

• Chewable tablets: 250 mg, 500 mg, 750 mg, 1000 mg

• Effervescent tablets: 500 mg, 1000 mg

• Oral suspension: 250 mg/5 mL, 500 mg/5 mL

• Sachets: Combination products with Vitamin D3 (commonly 500–1000 mg calcium + 400–1000 IU Vitamin D3)

INDICATIONS + DOSING — FOR CLINICIAN USE ONLY

Primary Indications (Approved / Standard in India)

1. Calcium Supplementation in Deficiency States (Hypocalcaemia, Osteomalacia, Osteoporosis Prevention/Treatment)

ADULTS:

Parameter Recommendation

Starting dose 500–600 mg elemental calcium once or twice daily

Titration Increase by 500 mg increments based on serum calcium and clinical response

Usual maintenance dose 1000–1200 mg/day elemental calcium in divided doses

Maximum dose 2000 mg/day elemental calcium (unless otherwise directed by specialist)

Clinical Notes:

• Best absorbed when given in doses ≤500 mg at a time

• Administer with meals for optimal absorption (acid-dependent solubility)

• Divide doses if total daily requirement exceeds 500 mg

1. Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) — Hyperphosphatemia (as Phosphate Binder)

ADULTS:

Parameter Recommendation

Starting dose 1000–1500 mg elemental calcium/day in 2–3 divided doses with meals

Titration Increase by 500 mg increments based on serum phosphate levels

Usual maintenance dose 1500–3000 mg/day in divided doses with meals

Maximum dose Total elemental calcium from diet + supplements should not exceed 2500 mg/day

Clinical Notes:

• Monitor calcium × phosphate product regularly (target <55 mg²/dL²)

• Considered second-line in many Indian nephrology protocols

• Sevelamer preferred if hypercalcaemia present or at risk

• Concurrent monitoring of serum calcium, phosphate, and PTH mandatory

Secondary Indications – Adults (Off-label)

Indication Dose Duration Specialist Only Evidence Basis

Dyspepsia (as antacid) — OFF-LABEL 500–1000 mg orally, up to 3–4 times/day as needed Short-term relief only (≤2 weeks) No Traditional use; widespread OTC practice in India

PAEDIATRIC DOSING (Specialist Only)

Primary Indication 1: Calcium Supplementation in Deficiency States

Age-based Daily Requirement (Elemental Calcium):

Infant <6months 200 mg/day Not Applicable 200 mg/day 200 mg/day

6-12 months 260 mg/day Not applicable 260 mg/day 260 mg/day

1-3 years 350 mg/day Increase based on clinical need 700 mg/day 700 mg/day

4-8 years 500 mg/day Increase based on clinical need 1000 mg/day 1000 mg/day

9-18 years 650 mg/day Increase based on clinical need 1300 mg/day 1300 mg/day

Clinical Notes:

• Divide total dose into 2–3 doses; administer with food for optimal absorption

• Use oral suspension or chewable tablets depending on age and swallowing ability

• Monitor for GI symptoms and hypercalcaemia with higher doses

Primary Indication 2: Rickets / Vitamin D-Resistant Rickets (Combined with Vitamin D)

PAEDIATRIC:

Parameter Recommendation

Starting dose 50 mg/kg/day elemental calcium in divided doses

Titration Increase to 75 mg/kg/day based on serum calcium and phosphate

Usual maintenance dose 50–75 mg/kg/day in divided doses

Maximum dose 75 mg/kg/day (specialist guidance required)

Clinical Notes:

• Specialist management mandatory

• Monitor serum calcium, phosphate, alkaline phosphatase, and PTH levels

Secondary Indications – Paediatrics (Off-label)

Indication Dose Duration Specialist Only Evidence Basis

Phosphate binding in paediatric CKD-MBD — OFF-LABEL 30–50 mg elemental calcium/kg/day in divided doses with meals As per nephrologist guidance Yes — Paediatric nephrology mandatory Indian paediatric nephrology protocols

⚠️ Not recommended below 6 months of age except under specialist supervision.

• Hypercalcaemia

• Hypercalciuria or nephrolithiasis (calcium-containing stones)

• Severe renal failure with uncontrolled calcium-phosphate imbalance

• Hypersensitivity to calcium salts or formulation excipients

• Elevated calcium × phosphate product (>55 mg²/dL²)

• History of calcium-containing kidney stones

• Concurrent high-dose vitamin D therapy (increased hypercalcaemia risk)

• Sarcoidosis or other granulomatous diseases (enhanced calcium absorption)

• Cardiac arrhythmias (monitor if hypercalcaemia develops)

• Achlorhydria or hypochlorhydria — absorption reduced; consider soluble calcium salts (citrate) in elderly or chronic PPI users

• Concurrent digoxin therapy — hypercalcaemia potentiates toxicity

• Immobilized patients (increased risk of hypercalcaemia)

Parameter Recommendation

Overall safety Considered safe throughout pregnancy when used within RDA limits

Preferred alternatives No specific alternative needed; calcium carbonate is first-line for supplementation

When to use Prevention/treatment of pregnancy-associated osteomalacia or hypocalcaemia; routine supplementation in second and third trimesters

Monitoring Serum calcium with higher doses; especially if co-administered with Vitamin D

Parameter Recommendation

Breastfeeding compatibility Compatible at nutritional supplementation doses

Preferred alternatives None needed; calcium carbonate is acceptable

Expected drug levels in milk Low (physiological regulation of calcium in milk)

Infant monitoring Rare: monitor for signs of hypercalcaemia (vomiting, poor feeding, constipation)

Parameter Recommendation

Starting dose 500 mg elemental calcium/day

Titration Increase gradually based on serum calcium and clinical need

Extra risks Constipation; poor absorption due to achlorhydria; vascular calcification risk with high-dose use in CKD

Clinical note Use chewable or effervescent forms in those with low gastric acid or difficulty swallowing; calcium citrate may be preferred in chronic PPI users

Interacting Drug Mechanism/Effect Recommendation

Oral bisphosphonates (alendronate, risedronate) Reduced bisphosphonate absorption Separate by at least 30–60 minutes; take bisphosphonate first on empty stomach

Tetracyclines (doxycycline, minocycline) Chelation → reduced antibiotic absorption Separate by at least 2 hours

Fluoroquinolones (ciprofloxacin, levofloxacin) Chelation → reduced antibiotic absorption Separate by at least 2 hours (preferably 4 hours)

Levothyroxine Reduced absorption → therapeutic failure Separate by at least 4 hours

Thiazide diuretics Increased calcium reabsorption → hypercalcaemia risk Monitor serum calcium; reduce calcium dose if needed

Iron supplements Reduced iron absorption Separate by 2–4 hours

Interacting Drug Effect Recommendation

PPIs, H2 blockers Reduced calcium carbonate absorption (requires acidic environment) Take with meals; consider calcium citrate in chronic PPI users

Digoxin Hypercalcaemia increases digoxin toxicity risk Monitor serum calcium and digoxin levels

Glucocorticoids Long-term use decreases calcium absorption Calcium supplementation often needed; monitor

Phenytoin Reduced calcium absorption; calcium may reduce phenytoin absorption Separate doses; monitor phenytoin levels

Isoniazid Reduced isoniazid absorption Separate by at least 2 hours

• Constipation (most common)

• Bloating and flatulence

• Chalky taste

• Nausea (at high doses)

• Belching (especially with effervescent formulations)

• Hypercalcaemia — especially with concurrent high-dose vitamin D; presents as confusion, polyuria, nausea, cardiac arrhythmias

• Nephrolithiasis (calcium oxalate stones) — especially if fluid intake is inadequate

• Milk-alkali syndrome — rare; occurs with high calcium doses + alkali intake; presents as hypercalcaemia, metabolic alkalosis, and renal impairment

⚠️ Serious hypercalcaemia requires immediate discontinuation and supportive management.

Phase Parameters

Baseline Serum calcium, phosphate, renal function (if risk factors present); dietary calcium intake assessment

During therapy (CKD patients) Serum calcium, phosphate, and PTH every 4–12 weeks; calcium × phosphate product

Long-term use Periodic serum calcium and renal function; assess for signs of hypercalcaemia (polyuria, constipation, confusion)

• Shelcal

• Ostocalcium

• Calcirol-C

• Calcium Sandoz

• Supracal

• Citracal

Common FDCs: Shelcal HD (with Vitamin D3), Shelcal 500, Supracal D3

Note: Not under NLEM price control when used as supplement

• Calcium carbonate requires acidic gastric environment for optimal absorption — administer with meals

• For elderly or chronic PPI users, calcium citrate or effervescent formulations may be preferred due to better absorption independent of gastric pH

• Split doses exceeding 500 mg into two or more times daily for better GI tolerance and absorption

• Avoid concurrent administration with antibiotics (tetracyclines, quinolones) and iron — reduced bioavailability

• Long-term use in CKD requires meticulous calcium-phosphate balance monitoring; consider sevelamer if hypercalcaemia risk is high

• Assess dietary calcium intake before prescribing supplements to avoid excess and hypercalcaemia

Calcium Carbonate; calcium supplementation; osteoporosis; CKD-MBD; hyperphosphataemia; phosphate binder; pregnancy-safe; paediatric rickets; renal-caution; bone health; OTC

RxIndia v1.0 — 30 Jan 2026

• CDSCO Formulations List

• Indian Pharmacopoeia (IP)

• AIIMS 2023 Drug Formulary

• API Textbook of Medicine

• ICMR Guidelines on Nutritional Requirements 2020

• Indian Academy of Paediatrics (IAP) Guidelines

• Indian Society of Nephrology practice protocols for CKD-MBD