Preventive Calcium Dose for an 18kg Child
For an 18kg child requiring preventive oral calcium supplementation, administer 180-288 mg of elemental calcium per day (10-16 mg/kg/day), ensuring total daily intake from diet plus supplements reaches 100-200% of the age-specific Dietary Reference Intake. 1, 2
Weight-Based Dosing Framework
The most recent guidelines establish a clear weight-based dosing range for children aged 1-18 years:
- Standard dose: 10-16 mg/kg/day of elemental calcium 1, 2
- For an 18kg child: 180-288 mg/day (calculated from the weight-based range)
- This represents supplementation only; total intake must account for dietary calcium 1
Age-Specific Context
The exact dose within this range depends on the child's age and current dietary intake:
- If age 1-5 years: Target total daily intake of 800 mg/day (100% DRI) to 1,600 mg/day (200% DRI maximum) 3
- If age 6-10 years: Target total daily intake of 800-1,200 mg/day (100% DRI) to 2,400 mg/day (200% DRI maximum) 3
- Subtract current dietary calcium from target to determine supplementation needed 1
Practical Dosing Algorithm
Step 1: Estimate dietary calcium intake (typically 500-700 mg/day in children with average dairy consumption) 1
Step 2: Calculate supplementation needed:
- If dietary intake is 700 mg/day and child is 6-10 years old, supplement with 100-500 mg/day to reach 800-1,200 mg total 1
- Use the lower end (100% DRI) for children with normal dietary intake 1
- Use higher supplementation only if dietary intake is inadequate 1
Step 3: For this 18kg child, the weight-based calculation (180-288 mg/day) serves as a reasonable starting point, adjusted based on dietary assessment 1, 2
Supplement Form Selection
Calcium carbonate is the preferred oral supplement due to cost-effectiveness and highest elemental calcium content (40%) 1, 4, 5
- Must be taken with meals for optimal absorption 5, 6
- Alternative forms contain less elemental calcium: calcium acetate (25%), calcium lactate (13%), calcium gluconate (9%) 1, 4
- Maximum single dose: 500 mg elemental calcium to optimize absorption 5
If the child requires 250 mg/day supplementation using calcium carbonate, prescribe 625 mg of calcium carbonate salt (250 mg ÷ 0.40 = 625 mg) 1, 4
Essential Cofactor
Vitamin D 600 IU/day is mandatory for optimal calcium absorption in children aged 1-18 years 1
Critical Pitfalls to Avoid
- Never exceed 2,500 mg/day total calcium intake in children ≥9 years (approximately 200% of DRI) 1
- Never use calcium chloride orally as it causes metabolic acidosis 1, 2
- Avoid calcium citrate in children with kidney disease due to enhanced aluminum absorption 1
- Do not give calcium carbonate on an empty stomach as gastric acid is needed for absorption 5
- Avoid single doses >500 mg elemental calcium as absorption efficiency decreases 5
Monitoring Considerations
For children on long-term supplementation, periodic monitoring of serum calcium, phosphorus, vitamin D, and bone mineral status is required to prevent metabolic bone disease 7, 2
The parenteral nutrition guidelines (0.25-0.4 mmol/kg/day = 10-16 mg/kg/day for ages 1-18 years) provide the physiologic basis for oral supplementation dosing, though oral requirements account for approximately 50-60% absorption efficiency 7, 2