What blood tests are taken in the emergency room (ER)?

Ken Szwak, PA-C
Emergency Medicine Specialist

Blood tests that are ordered in the emergency room (ER) depend on what the patient complains of and the results of his or her exam.

  • The most common blood tests ordered in the ER are a complete blood count (CBC) and a basic metabolic panel (BMP). A CBC measures several components and features of your blood, including white blood cells (which fight off infection), red blood cells and hemoglobin (which help carry oxygen to your organs and other tissues), hematocrit (the proportion of red blood cells to the fluid component, or plasma, in your blood) and platelets (which are partially responsible for clotting). A BMP measures the balance of electrolytes like sodium and potassium, kidney function and glucose levels.
  • If you come to the ER for chest pain and your healthcare providers are concerned about a possible heart attack, they might add a troponin test, which measures enzymes produced when there is damage to the heart. They might also order a prothrombin time test (PT/INR), which is another measure of how the blood is clotting.
  • In diabetic emergencies, your healthcare provider might add an acetone level and an arterial blood gas (or venous blood gas) to determine your blood’s pH levels.
  • If you are a patient with preexisting liver disease (or it is suspected), you may also have blood tests ordered to check your liver function, including aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and bilirubin, as well as an ammonia level (which may be elevated if your liver is failing). If they are concerned about a gallbladder attack or pancreatitis, your healthcare providers might add amylase and lipase levels to the above liver blood tests.
  • If they are concerned about complications with an early pregnancy, they might add a quantitative human chorionic gonadotropin (hCG) blood test, which measures the hormone produced during pregnancy as well as blood type and Rh.
  • In severe infections (sepsis) they would add blood cultures.

Keep in mind these are just some scenarios. Again, the patient's complaint and exam findings point doctors in the direction they need to go. It's also important to know that non-blood lab tests like urine tests and skin and genital cultures, not to mention EKGs, x-rays and CT scans, are used in conjunction with blood tests.

Trinity Health is a Catholic healthcare organization that acts in accordance with the Catholic tradition and does not condone or support all practices covered in this site. In case of emergency call 911.This site is educational and not a substitute for professional medical advice; always seek the advice of a qualified healthcare provider.

Dr. Kathleen Handal, MD
Emergency Medicine Specialist

A visit to the ER wouldn’t be complete without some type of test. The basic blood tests you might encounter include:  

  • Complete Blood Count (CBC) — they are ordered “ stat.” STAT comes from the Latin word “statim” which means immediately. A CBC provides a general picture of your blood levels. It’s typically ordered for complaints such as fatigue, weakness, inflammation, bruising, fever and bleeding. It is an automated count of the cells in your blood that includes information on the number, shape and size of your cells. A standard CBC includes eight pieces of information.
  • White Blood Cell (WBC) — count helps to identify infection, immune problems, cancer and leukemia. If the numbers are high or low, further testing is usually required.
  • Red Blood Cell (RBC) — count helps to identify anemia if decreased.
  • Hemoglobin (HGB) — measures the oxygen-carrying proteins in the blood. When low, it indicates blood loss and anemia which can be life-threatening.
  • Hematocrit (HCT) — measures the percentage of red blood cells in a given volume of blood. Again, if the level is low, anemia is indicated.
  • Platelets — looked at to identify problems related to bleeding and clotting.
  • Basic Metabolic Panel (BMP)—checks the electrolyte and mineral levels in the blood that are so important for keeping your muscles, heart, kidneys and other organs working properly. Included here is your level of: Sodium (Na), Potassium(K), Chloride (Cl), Creatine (Cr), Blood Urea Nitrogen (BUN), Bicarbonate(HCO3), Glucose (Glu). 

If your care involves going to the operating room, blood tests will be necessary and possibly an ECG.

TIP: Don’t bother to ask for routine exams like your Pap smear or prostrate exam or to have your prescriptions refilled. Now is not the time to deal with these issues. We’re focusing on the problem that brought you into the ER.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.