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Lab Tests FAQ

What is a medical laboratory or lab?

A laboratory (lab) is any facility that performs laboratory testing on specimens taken from humans to give information for the diagnosis, prevention, treatment of disease, or assessment of health. The Clinical Laboratory Improvement Amendments of 1988 (CLIA ’88) are federal guidelines for the regulation of laboratory testing to ensure the accuracy, reliability and timeliness of patient test results regardless of where the test was performed. The Centers for Medicare & Medicaid Services (CMS) oversees the implementation of CLIA and is responsible for the oversight of these regulations in laboratory settings. Laboratories are required to be inspected and re-accredited every two years.

What are medical lab tests?

Lab tests are examinations performed on blood, body fluids, tissues and other substances in order to determine what is normal or what is abnormal for you as a patient.

Why are medical lab tests performed?

According to the Journal of Applied Laboratory Medicine, lab tests are considered to be among the most important and frequently used variables that influence medical decisions. Your doctor may request one or many lab tests depending on your condition. Your doctor uses lab results to identify changes in your health condition, diagnose a disease or condition, plan your treatment, evaluate your response to a treatment, or monitor the course of a disease over time.

Who can order medical lab tests?

Only your doctor or other authorized ordering healthcare provider can order lab tests. Patients cannot order their own tests.

What should I expect my lab process to be like?

Once you receive your lab test order, confirm with your healthcare provider about any lab test preparation instructions. You may be asked to fast (stop eating for a period of time), drink more or less water than usual and/or avoid certain medications before the test. A diagnostic lab order can be printed or digital. If your healthcare provider does not give you a printed lab order, please contact them prior to your lab visit to confirm that it was sent electronically.

For your convenience, Memorial Herman Diagnostic Laboratory locations are walk-in labs – no appointment is necessary. Wait times will vary depending on the number of patients, and are typically longer in the mornings.

To find a Memorial Hermann Diagnostic Laboratory location near you click here.

Is fasting required before my diagnostic lab test?

Some lab tests require you to fast beforehand. If your healthcare provider orders a fasting test, you should not eat or drink any liquids, except for water, for 12 hours prior to the test. Two common fasting blood tests are glucose and lipid panel.

Can I take my medications before I have medical lab tests?

This will vary by lab test. Unless your doctor says otherwise, take your usual medications. If you are taking vitamin/mineral supplements, ask whether you should continue those as well. If you are uncertain, please consult with your doctor.

Why do you need more than one tube of blood?

We strive to draw the minimum amount of blood required for the tests your doctor has ordered. The number of tubes required will vary for each test, but we will only collect what is needed at the time of collection.

Who performs the testing on laboratory specimens?

Lab testing is performed in our Memorial Hermann Diagnostic Laboratories by qualified, licensed phlebotomists who range in years of experience. Testing personnel must satisfy rigid accreditation standards set forth by the federal Clinical Laboratory Improvement Amendments of 1988 (CLIA ’88).

What do Pathologists do?

Pathologists are physicians specialized in the study of diseases by analysis of tissue, cell, and body fluids from various parts of the body. In general, the field of pathology addresses the cause of the disease, how it developed, what cells changes it originated and its consequences. They deal with establishing the source, cause and staging of various disease processes in order to help in making accurate and early diagnoses. They are trained in conducting biopsies, studying and analyzing tissue samples to make a pathological diagnosis like a fibroma, cancer, infection or stage a cancer to help decide the line of treatment. All pathologists in our directory are board certified or board eligible specialists after completion of a residency in pathology following medical school. To learn more about our pathology services, click here »

When will my test results be available?

Multiple factors affect how soon test results are available. Most test results are available within a week. Many test results are available within 4 to 24 hours. Below are three common test collections to consider.

Tissue specimens, such as a tumor that is being analyzed for cancer, may take days to complete due to the numerous, complex steps that must be performed to process the specimen and requests for additional studies. Specimens submitted to be tested for bacteria or other microorganisms are cultured so the organisms can grow to a level where it can be seen.

Routine cultures, like strep throat or urinary tract infections, take a minimum of 24-48 hours to grow.

Other cultures for tests like tuberculosis, may take up to 21 days to grow.

Positive cultures require additional steps such as organism identification and susceptibility to antibiotics. Other specialized tests may be sent to an outside reference laboratory; this may lengthen the turnaround time.

You can also ask your doctor for additional information on timeframes for receiving test results.

Can I receive a copy of my test results?

Patients are encouraged to obtain their lab test results from their doctor. You may also access your test results through our patient portal, Everyday Well.

Lab results are reported only to the ordering doctor or other authorized ordering healthcare provider.

Can you tell me what the lab results mean?

Lab results are only a part of the total diagnostic picture of your health. Our phlebotomists have limited information available to them regarding your personal records, and they are unable tell you why a test was ordered or what the results mean. Many tests have more than one purpose and only your ordering doctor is at liberty to discuss your test results. Lab personnel are not allowed to interpret test results for our patients. Please speak with your doctor for more information about your lab results.

I am a hospital inpatient. Why are my blood specimens collected so early in the day?

Blood samples are collected primarily during the early morning hours beginning at 3 a.m. and continue until 6:30 a.m. so that most of the laboratory results are available to your doctor by 7 a.m. It is important to have the results by 7 a.m. for doctors to make decisions about the patient’s condition and treatment for the day. Blood specimens can be collected throughout the day, depending on the patient’s treatment plan set forth by the doctor. In some cases, blood must be obtained at timed intervals in order to monitor specific conditions like cardiac enzymes for cardiac problems or to determine a diagnosis like a glucose tolerance test for diabetes.