Medical Specialty >> Hematology

Doctors Lounge - Hematology Answers

Back to Hematology Answers List

If you think you may have a medical emergency, call your doctor or 911 immediately. Doctors Lounge ( does not recommend or endorse any specific tests, physicians, products, procedures, opinions, or other information that may be mentioned on the Site.

DISCLAIMER: The information provided on is designed to support, not replace, the relationship that exists between a patient/site visitor and his/her physician. Please read our 'Terms and Conditions of Use' carefully before using this site.

Date of last update: 10/12/2017.

Forum Name: Hematology Topics

Question: Blood Work

 browneyes77s - Tue Jul 08, 2003 5:33 pm

I went for my early physical today and needed blodd work to test for thyriod. Also, some other blood tests that are normally done for this visit. I went to the place to do the blood and the nurse asked if i had eaten today and i said "yes". She then replied "ok we will take your blood anyway". I was under the impression you had to fast for several hours before this type of blood work. Are you? And if so, will this throw off my results?
 Dr. Tamer Fouad - Thu Jul 10, 2003 1:59 pm

User avatar Fasting is required only for certain tests. The most commonly ordered tests that require fasting are:
lipid panels
fasting blood sugar
Fasting means nothing but water for ten to 12 hours.
To the best of my knowledge you don't need to fast to get a thyroid function test. Anyone else care to add to this / correct me?
 catrina - Thu Sep 18, 2003 12:19 pm

I am not a doctor, however, I do have the thyroid blood test yearly, sometimes more often if my weight changes or my levels fluctuate - I have been on synthroid for over ten years now. No, It is not necessary to fast - I have yet to do so, and my test results are where they need to be. I have read articles that indicate fasting is necessary, however my doctors over the years have NEVER told me that this is required, nor has the subject ever come up. The only requirement that they ask to be met, is take the synthroid at the SAME TIME every day, and on an empty stomach. Hope this response from a layman is helpful, Doctor Fouad.

| Check a doctor's response to similar questions

Are you a Doctor, Pharmacist, PA or a Nurse?

Join the Doctors Lounge online medical community

  • Editorial activities: Publish, peer review, edit online articles.

  • Ask a Doctor Teams: Respond to patient questions and discuss challenging presentations with other members.

Doctors Lounge Membership Application

Tools & Services: Follow DoctorsLounge on Twitter Follow us on Twitter | RSS News | Newsletter | Contact us