Vitamin K-dependent cofactor for Activated Protein C (APC). Circulates free and bound to C4b-binding protein; only free form is active. Deficiency is an inherited thrombophilia risk factor.
| Sex | Age | Range | Notes |
|---|---|---|---|
| Female | 18–50 yrs | 60 – 130 | Premenopausal female (lower in OCP/pregnancy) |
| Female | ≥ 50 yrs | 70 – 140 | Postmenopausal female |
| Male | ≥ 18 yrs | 70 – 140 | Adult male; total and free measured |
⚠ Clinical Note
Reference ranges are indicative. Always interpret results in the context of the individual patient and local laboratory reference intervals, which may vary.