Main content

    Learning About Your Health

    Blood Test

    Printer-friendly PDF of Blood TestOpens new window (72KB)
    (Download a free copy of Adobe Acrobat ReaderOpens new window)

    Having a Blood Test

    Your doctor recommends testing your blood as part of your continuing medical care. A phlebotomist – a person trained and certified to draw (collect) blood – provides your care. If you have any concerns or questions about your blood draw, please ask your phlebotomist. Also, please let the staff know if there is anything they can do for you during your visit.

    Back to top

    Preparing for Your Blood Test

    You do not need to prepare for most blood tests. However, your doctor will tell you if special preparation is needed (see guidelines below).

    Your doctor gives you a form called a requisition that lists the blood tests ordered for you. Bring this form with you to the blood test.

    Special Preparation Guidelines:

    • For Cholesterol, Glucose, and Glycohemoglobin Blood Tests: You must fast for 12 hours prior to the blood test, unless your doctor tells you otherwise. Fasting means no eating or drinking for 12 hours before the test, except water. You may resume your regular diet after the test.

    • For a 3-Hour Glucose Tolerance Test (3-Hour GTT): Call the Clinical Laboratory at (415) 600-2200 to schedule this test and receive preparation instructions.

    • For Patients Taking Blood-Thinning Medications, such as Heparin or Coumadin (Warfarin): Tell the phlebotomist before your blood is drawn if you are taking any blood-thinning medications. After your blood is drawn, the phlebotomist applies pressure to the site until no blood is seen on the gauze.

    Back to top

    Waiting to Have Your Blood Drawn

    Scheduled blood tests are usually done on time. For scheduled and routine testing:

    1. Register with the staff when you arrive for your blood test.

    2. Wait while a phlebotomist processes your doctor’s order.

    3. The phlebotomist will call you to have your blood drawn.
    The staff works hard to quickly and accurately complete your blood draw, but there may be delays. The staff will keep you informed of any delays. If you have any questions or concerns, please see the greeter at the entrance of the draw site.

    Back to top

    Where to Go for Your Blood Draw

    Outpatient labs are conveniently located at each of our campuses and downtown San Francisco. With your physician's lab slip, you can undergo any outpatient laboratory test required for diagnostic screening, including blood testing, urinalysis, and microbiological cultures.


    Back to top

    During Your Blood Test


    1. A phlebotomist guides you to an area called a drawing station for your privacy.

    2. The phlebotomist prepares your arm by wiping the puncture site with alcohol. The alcohol cleans the area to prevent infection.

    3. The phlebotomist ties a tourniquet (a wide rubber strip) around your arm.

    4. The phlebotomist inserts a thin needle into the vein. You may feel a pinch when the needle is inserted.

    5. Once the blood collection tube(s) are filled, the phlebotomist removes the needle.

    6. The phlebotomist applies pressure to the puncture site and covers the site with a clean gauze pad.

    Back to top

    After Your Blood Test

    • There may be some mild bruising around the puncture site. You may remove the clean gauze pad after the test.


    • If you are taking blood-thinning medications, the phlebotomist applies additional pressure to the puncture site. You may go home once the bleeding at the puncture site has stopped.

    Back to top

    Getting Your Blood Test Results

    Blood test results are usually sent to your doctor within 1 - 2 days. However, if your blood test is sent to a reference laboratory, the results are usually sent to your doctor within 5 - 7 days.

    Back to top

    When to Call Your Doctor

    Call your doctor if you notice any increased bleeding, bruising, pain, or swelling at the puncture site.

    Back to top

    More Ways to Learn

    Go to Lab Tests Online Opens new window.


    Frequently Asked Questions

    Question: How do I prepare for my blood test?
    Answer: Most blood tests do not require preparation. Your doctor tells you how to prepare for your blood test if needed.

    Question: Will I have to wait to have my blood drawn?
    Answer: Most blood draws take about 15 minutes. The staff informs you if there are any delays.

    Question: Who will draw my blood for the test?
    Answer: An experienced and certified phlebotomist draws your blood.


    Produced by the Center for Patient and Community Education in association with the staff and physicians at California Pacific Medical Center. Last updated: 3/2011


    Funded by: A generous donation from the Mr. and Mrs. Arthur A. Ciocca Foundation.

    Note: This information is not meant to replace any information or personal medical advice which you get directly from your doctor(s). If you have any questions about this information, such as the risks or benefits of the treatment listed, please ask your doctor(s).

    Back to top