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1070570 tn?1283436213

taking meds before drawing blood

Are you supposed to take your thryoid meds the morning that you get your blood drawn for thyroid tests? I have heard A) that you should take it bc that will be a more representative picture of how you feel everyday
and B) no you shouldn't becuase it will distort your levels since you have just taken the meds that morning and they're still circulating in the blood. My doctor didn't instruct me whether or not to take them so I did.

What does your doctor tell you?
8 Responses
988694 tn?1332359479
For mistake I took my medicine one time that I had  some blood work.
My FT3 was so high that I did not understand how I was still breathing.

My doctor repeated my tests. I did not take my meds as always. My FT3 was pretty much in range.

My FT4 and TSH never changed. I would say that if you are taking FT3 meds, do not take your medicine before blood work.
734073 tn?1278896325
Not to take them untill after labs are drawn.
1070570 tn?1283436213
thanks for the response!

so taking my meds an hour before my April blood tests probably REALLY SKEWED my results...great now I really have no idea.

My July test...I had taken the cytomel and synthroid that morning but didn't have the blood drawn until abour 2:30 p.m.

It seems like my doctor would have been more specific and told me to NOT take my meds...

Avatar universal
Endo told me to take all my medications as usual before my lab test.  He said the level of tsh in bloodstream is an accumulation based on about a 7 day period, not how much you've taken that day. (otherewise we wouldn't have to wait 4-6 weeks before being retested).  Also said lab tests MUST be done before 9AM when thryroid hormone levels are at there peak, and then the same time for future labs.
798555 tn?1292787551
"It seems like my doctor would have been more specific and told me to NOT take my meds..."

- No, they dont look at it that way, since they tend to think anything in range is OK.

T4 levels wont change a whole lot, but T3 levels will instantly go up some if blood draw is taken after.

Morning before med is the best time for thyroid blood draw. Some labs are open Sat morning.
649848 tn?1534633700
COMMUNITY LEADER
"Endo told me to take all my medications as usual before my lab test.  He said the level of tsh in bloodstream is an accumulation based on about a 7 day period, not how much you've taken that day. (otherewise we wouldn't have to wait 4-6 weeks before being retested).  Also said lab tests MUST be done before 9AM when thryroid hormone levels are at there peak, and then the same time for future labs."

I totally disagree.  TSH can fluctuate throughout the day, so is not an accumulation based on a 7 day period.  It's the FT4 that has to accumulate over a period of time, which is why we have to wait 4-6 weeks for retesting.  This is to be able to tell if the T4 med is adequately raising hormone levels and being converted properly to T3 as needed.

In addition, if your thyroid is producing hormone on its own, the peak may be before 9 AM.  I doubt seriously that this would be true for those of us who are dependent on thyroid hormone replacement.

I always have my labs drawn BEFORE I take my med, which is even more important if I'm having other blood tests done as well, such as a lipid panel, etc.
Avatar universal
I have had dealt with thyroid test for the last 16yrs and not once did they ever tell me NOT to take my med before lab work.

I guess every doctor is different, but I have had my PCP, Infectious disease doctor, GI, OB, urologist, neurologist, opthamologist, and endocrinologist test my TSH levels & they, not ONE of them, ever told me not to take my thyroid med before lab work.
798555 tn?1292787551
T3 levels if on a T3 med will soar if taken before blood draw. I have seen proof and so have others.
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649848 tn?1534633700
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