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Do I really need to fast before having bloodwork done??

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ugh, I have to have my blood taken this week for some tests & I'm not looking forward to it.  I know it's pretty much quick & painless, but I always faint even when I'm laying on the cot & that's not a very enjoyable experience.  The only time I haven't fainted is when I've eaten beforehand for a blood test to see if I was allergic to wheat gluten.  For everything else, I'm told I have to fast & my question is WHYYYYYYYYY? 

Would it really screw up the tests that badly if I have a little something to eat in the morning in the hopes that I don't pass out & have to be brought to with smelling salts?  (At least I think it's called smelling salts).  Can I at least have a bowl of Grape Nuts cereal & a bagel before having my blood sucked out of me?  Or would it mess up the tests?  I have to bloodwork done to check my cholesteral, thyroid, gluten, and a couple others that I have no idea what they are for.  Please let me know. Undecided

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they wouldn't ask you to fast if they didn't have good reason.

They expect you to fast before the draw your blood so they have your baseline levels.  One time I was not explicitly told to fast before I got blood drawn (it was being done somewhere between 10 and 11am) so I had a bowl of Quaker Apple Cinnamon oatmeal.  When my doctor got the results he asked about my elevated sugar level (prolly assuming i was showing signs of diabetes). My best suggestion for you is to drink lots of water the day of and schedule the appt. early in the day.  Also you only need to stop eating and drinking (all but water) from midnight until your appt.

Here's a little anecdote I hope will make you feel better...I had to have a liver biopsy and you have to fast for those too.  My biopsy was supposed to happen at 10am...but the doctor didn't show up until after 12...I didn't get to eat anything until almost 2pm because you have to lay on your side and not eat anything for an hour afterwards.  There are worse situations, hon. :) Grin and bear it.

Hi there,

I'm a nurse and just thought I'd answer your question...

Fasting before having your cholesterol/triglycerides checked will give you an accurate idea of what your blood levels truly are. When you eat food the nutrients are absorbed into your blood stream ( including glucose/ cholesterol) if you eat before the blood test it will not be as accurate. 

If you're not sure what they are testing for you should ask!!! You can never ask too many questions!! Take something with you to eat once your test is done!!

Hope this helps, good luck! Smile

They're not going to get an accurate result if you've been eating before your tests... my friend was told she was diabetic because her blood sugar was too high, but it was only because she'd had a coke and a donut for lunch!

Eat something right before you go to bed the night before, and get your blood test done as early as you can in the morning, and take something to eat immediately afterwards.

I've only had to fast for cholesterol checks.  I went in one day for a routine physical w/blood draw and mentioned that I hoped they'd push me through because I hadn't eaten anything yet (fasting).  The receptionist asked me why I was fasting, and I said because I thought I was supposed to before a blood draw.  She chuckled and said to fast (for me) only with a cholestrol check.  The nurse ended up trying to get my blood 3 times and said it was probably because I hadn't drank anything either and was dehydrated.  Live and learn. Yell

Yes,  That is the only way as the nurse above said to get accurate readings of your blood work up.Frown  You can drink water and plain black coffee though.  Atleast that is what my dr. requires.  They do the cholestrol and all the other junk to.  I also take snack to eat right after they draw the blood.

Good Luck







I just had my blood drawn over the weekend.  I was told to fast for 12 hours.  It's no big deal.  I didn't eat after 9:00pm and then I had the test around 10:00am...I don't eat between those hours anyway. 


The reason is what the nurse said they need to get your baseline levels.  If you eat something right before your sugar counts could go up and the doctors might think something is wrong when there's not.  I have to have blood tests every week (medical reasons) and I hate having my blood taken even after 2 1/2 of this I still can't watch them take it. 

My suggestion would be to eat something late at night like oatmeal or something like that so that it stays in your stomach longer but won't effect your tests.  I have also been told by my doctors that as long as you don't eat within 8 hours of the tests that the numbers are accurate so dedpending on what time your test is you could always get up in the middle of the night and eat something then too.

Hope everything goes well.

oh shoot, I was afraid of that.  I just hate fainting & it happens every time I get my blood drawn when I fast beforehand.  well, there are worse medical procedures to go through than getting your blood drawn, so I'll just bring my orange juice & a couple of doughnuts to munch on after the phlebotomist revives me with the smelling salts....

Just call me "Ms. Wimp." Undecided

I've never fainted but I agree that fasting does suck! One time I was told not to eat after 10pm the night before and my test was at noon the next day. I didn't end up eating until after 2pm. I was absolutely starving. Like a few ppl mentioned, just be prepared with water and snacks so you can chow down right after they wake you up from your little power nap Wink

Hey, tahiti.  How did the blood draw go?   Did the Juice and doughnuts help afterwards?  I'm a needle wimp too.

Original Post by joerealistic:

Moderated text

 And you can stop bumping zombie threads

Edited Sep 15 2011 01:53 by coach_k
Reason: Previously moderated text quoted and removed

He has a problem??  Sounds like you have a problem not eating enough.  I am 5'10" and weigh right at 205 pds and have 12% body fat year round.   I eat 5,000. calories a day and 250 for breakfast is just a snack before 1st breakfast :)  

(Of course, running for 15-20 minutes + walking for 30 minutes + lifting weights and jumping rope for 45-60 minutes a day probably burns some calories??)   

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