Ryan McVay/Photodisc/Getty Images. Normal Calcium Levels in Adults. While normal blood calcium levels differ slightly from lab to lab, they usually range between 8.5 and 10.5 mg/dL (milligrams of calcium per deciliter of blood). Ionized calcium typically ranges from about 4.6 to 5.3 mg/dL. Jupiterimages/Pixland/Getty Images.