Important: Each laboratory must establish its own reference range.
| Normal Range (%) | Oral Anticoagulation Range FX (%) | Oral Anticoagulation Range Corresponding INR | Source |
| 60 – 120% | 15 – 35% | Not given | OHSU Ward Manual |
| 75 – 155% | 20 – 44% | Not given | Esoterix Coagulation Handbook |
| 20 – 40% | 2.0 – 3.0 | Mass General Hospital | |
| 20 – 40% | 2.0 – 3.0 | Rosborough T & Shepherd M. Unreliability of INR for Monitoring Warfarin Therapy in Patients with Lupus Anticoagulant. Pharmacotherapy 2004; 24(7): 838-842. | |
| 82 – 151% | 17 – 43% | 2.0 – 3.5 | Lab Corporation of America* *Reference: Moll et al. Monitoring Warfarin Therapy in Patients with Lupus Anticoagulants. Ann Intern Med 1997; 127:177-185. |
| 70 – 130% | 20 – 43% | 2.0 – 3.5 | Joyner KA. Monitoring OAT in Patients with Lupus Anticoagulants – Utility of the Chromogenic Factor X Assay. Clin Coag Lab, DUMC. |
| 11 – 42% | 2.0 – 3.5 | Moll S, Ortel T. Monitoring Warfarin Therapy in Patients with Lupus Anticoagulants. Ann Intern Med 1997; 127:177-185. | |
| 17 – 43% | 2.0 – 3.5 | Sanfelippo MJ et al. Falsely Elevated INRs in Warfarin-Treated Patients with the Lupus Anticoagulant. Wisconsin Medical Journal, June 2000; 62-64, 43. |