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Emergency Blood Tests


In the emergency room, blood tests are necessary to quickly gain information needed to manage and diagnose medical emergencies. A blood test involves withdrawing a sample of blood into a vial and sending it to a lab for analysis.

At Dignity Health, our emergency care team performs prompt, high-quality blood tests in the Bay Area.

Why Blood Tests are Performed

Emergency blood tests fall under the following general categories:

  • Blood bank tests allow doctors to determine the type of blood that could be compatible for transfusion. Examples include cross-matching tests for antibodies and blood typing.
  • Clinical chemistry tests give doctors information about substances in the blood that may be a sign of disease or organ dysfunction. Examples include enzymes, electrolytes, and hormones.
  • Drug levels show the amount of a drug in your blood. These tests may be necessary to identify drug toxicity or overdose due to acetaminophen (treats pain and reduces fever), phenytoin (controls seizures), digoxin (slows heart rate to treat atrial fibrillation), lithium (treats depression), ethanol (alcohol), and theophylline (treats respiratory diseases).
  • Hematology tests look at the amount of blood and plasma components and how they function. Examples include a complete blood count (CBC) and tests of blood clotting ability.
  • Microbiology tests tell doctors if there are fungi, bacteria, or parasites in the blood. Examples include cultures to grow the organism and sensitivity tests to find out which drugs will work to fight the infection.

What to Expect During an ER Blood Test

In the Dignity Health emergency room, a doctor, nurse, or technician will draw your blood to collect the sample. 

The health care provider who draws your blood will apply pressure to the site to stop the bleeding. You will have a small bandage with a cotton ball to absorb any residual blood. You can usually remove the bandage within a few hours.

Once the sample goes to the lab, it usually takes up to an hour to get the results. However, some tests may take more time to process. The doctor will discuss all test results with you and explain what it means for your care.

Rely on our emergency doctors to quickly work to diagnose your condition and provide personal care.

Dignity Health offers patients expert and efficient emergency care, including blood tests, in San Francisco, Santa Cruz, and Redwood City.