The CoaguChek XS PT Test strips are part of the CoaguChek XS System. The CoaguChek XS System measures blood‑clotting time for people who are taking anticoagulation medications such as Coumadin® or warfarin. The CoaguChek XS System uses blood from a fingerstick. The system is intended for properly selected and suitably trained users or their caregivers on the prescription or other order of the treating doctor. Users should be stabilized on anticoagulation medications such as Coumadin or warfarin prior to self‑testing with the CoaguChek XS System. Caution: These test strips are for use outside the body only. Do not eat the test strips.