Normal ranges vary slightly by lab, but total serum calcium is commonly reported around 8.6–10.3 mg/dL (2.2–2.6 mmol/L). Interpretation is not based on a single number: much of calcium is albumin-bound, so low albumin can make total calcium appear low while ionized calcium is normal. Clinicians may use corrected calcium calculations or measure ionized calcium for clarity. Sampling factors (tourniquet time, posture, hydration) can influence results. If calcium is low, vitamin D, parathyroid hormone (PTH), magnesium, and kidney function are often assessed together. If calcium is high, the cause of hypercalcemia must be investigated. Bottom line: blood calcium is not a direct “bone score”; bone health requires a broader framework including vitamin D, protein intake, and mechanical loading through exercise.