Female patient flexing arm after blood work in health care provider's office.

Why and when you need blood work

Blood work provides essential insight into how your organs are functioning.

Blood tests have multiple benefits, including:

  • Determining your risk status for disease and conditions
  • Checking treatment success
  • Early diagnosis of some conditions before symptoms or complications develop
  • Identifying treatment side effects
  • Monitoring chronic disease status and progression

How often should I have blood work?

It is common for your primary care provider (PCP) to order blood tests from time to time. If you are unsure about the tests, talk to your PCP and have them explain what the test is for and why you need it.

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The reason your PCP orders a blood test will likely depend on several factors, including:

  • Age
  • Chronic conditions under evaluation or treatment
  • Family history
  • Health screenings
  • Lifestyle
  • Medical history
  • Specific concerns

Mark Meeker, DO, an internal medicine physician and vice president of Community Medicine for OSF HealthCare, said that an acute illness, unexpected change in chronic disease and new history or physical findings most commonly lead to unscheduled blood work.

“The frequency of blood work is individualized based on a person’s situation and needs. It is influenced by sex, age, symptoms, diagnoses, medications and family history,” Dr. Meeker said. “Lab work requires an order from your PCP or specialty clinician to help guard against waste and harm from inappropriate testing.”

General screening blood tests are sex- and age-dependent and included in some wellness visits. The most important blood tests are those your PCP determines are necessary. These especially include those that monitor for medication effectiveness and side effects or safety.

Keep in mind that a medication or disease process has to affect specific levels of markers in the bloodstream for it to show up on a blood test.

“For example, a person may have a mass in their lung that’s visible through X-ray but has no effect on standard blood tests at that stage of the disease,” Dr. Meeker said. “That is why good care requires a history, listening to a person and a physical exam. We can observe and look for physical abnormalities and possibly blood tests or imaging studies to confirm history or physical suspicions to find an issue not heard or seen.”

Do I need to prepare?

While a few procedures and blood tests require you to follow specific guidelines, you usually don’t have to take any precautions.

“Most blood tests can be done and interpreted regardless of last meal or time of day you ate. There are a few blood tests that may need to be done fasting or at a specific time,” Dr. Meeker said. “Blood tests on levels of a few specific medications may need to be timed specifically before or after a scheduled dose, but your primary care provider should give you specific instructions in those rare occurrences.”

How soon can I expect to receive results?

With modern electronic health records, we have easy access to test results through online medical record platforms, like OSF MyChart.

How quickly results are available depends on the specific test.

“Most routine tests come back within hours, although some more complicated tests, or infrequent tests, may take a day or two,” Dr. Meeker said. “If the test is run only at specific reference labs, is complicated or infrequently done, it may take longer. There are times, too, when your clinician may want to have time to consider the results in the context of your situation before releasing them with no context or explanation.”

Last Updated: October 5, 2021

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About Author: David Pruitt

David Pruitt is a writer for the Marketing & Communications division of OSF HealthCare. He has a bachelor’s of journalism from Southern Illinois University Edwardsville and worked as a reporter before joining OSF HealthCare in 2014.

An avid golfer and fisherman, David was born and raised Alton, Illinois, which is where he currently resides with his son, James.

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Categories: General