What are the critical lab values a nurse must know for the NCLEX?

Critical lab values requiring immediate nursing action include potassium below 3.0 or above 6.0 milliequivalents per liter, sodium below 120 or above 160, glucose below 50 or above 400 milligrams per deciliter, hemoglobin below 7 grams per deciliter, platelet count below 50,000, INR above 4.0 for patients on warfarin, troponin above the upper reference limit, white blood cell count below 2,000 or above 30,000, and partial thromboplastin time above 100 seconds on heparin.