Calcium's value is real but narrower than its reputation. Its strongest benefit is skeletal: adequate intake slows age-related bone loss and, with vitamin D in deficient or frail people, reduces fractures. Food calcium also lowers kidney-stone risk, while supplements raise it and may unsettle heart safety. A food-first approach, filling only a measured gap, fits best. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Serum calcium (albumin-corrected) | 8.8–10.0 mg/dL | Detects hypercalcemia from over-supplementation |
| Ionized calcium | 4.6–5.3 mg/dL | Most accurate measure of biologically active calcium |
| 25-hydroxyvitamin D | 40–60 ng/mL | Governs calcium absorption; low levels blunt benefit |
| Parathyroid hormone (PTH) | 15–45 pg/mL (lower-normal ideal) | Elevated levels signal inadequate calcium/vitamin D and ongoing bone loss |
| 24-hour urinary calcium | 100–250 mg/24 h | Identifies hypercalciuria and kidney-stone risk |
| Phosphate | 2.5–4.0 mg/dL | Balances calcium metabolism; abnormal in kidney/parathyroid disease |
| Magnesium | 2.0–2.4 mg/dL | Needed for PTH and vitamin D function; competes with calcium |
| eGFR / creatinine | eGFR >60 mL/min/1.73 m² | Kidney function determines safety of supplementation |
| Coronary artery calcium (CAC) score | 0 (Agatston units) | Optional marker of arterial calcification for cardiovascular risk context |
Cadence: Baseline before higher-dose or long-term use, at about 3 months after starting or changing dose, then every 6–12 months