So I was getting my bloods done this morning and the nurse asked me what medication I had taken so I said just eltroxin 250mcg and the lady sitting across from me said “oh you shouldn’t have taken it before” (in fairness it was a good 2 hours earlier)
So this sparked a conversation between the nurses and they got two endos (surprised there was 2 on duty) to come down and explain that in order for an accurate blood result they need to see the results after the eltroxin has been taken and that it builds a reserve anyway so taking it after the bloods is pointless and just prolongs the fasting.
So I went away more confused so spoke to my consultant and he said that before is optimal but it doesn’t make a difference because it’s the reserve they are interested in.
Thoughts on this?
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Louiseb17
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That's not correct. The timing of Levo before a blood test affects FT4 level not TSH level. Taking Levo close to the blood test has the same effect as taking T3 close to the blood test, it gives a false high result. What affects TSH level is time of day the test is done, fasting and drinking caffeine containing drinks.
Louiseb17 To get the normal circulating level of FT4 it is advise to take your last dose of Levo 24 hours before the test, any longer and you get a false low, too close and you get a false high. One of our Admin's endocrinologist agrees with the advice given here for thyroid tests:
* Book the first appointment of the morning. This is because TSH is highest early morning and lowers throughout the day. If we are looking for a diagnosis of hypothyroidism, or looking for an increase in dose or to avoid a reduction then we need TSH to be as high as possible.
* Fast overnight - have your evening meal/supper as normal the night before but delay breakfast on the day of the test and drink water only until after the blood draw. Eating may lower TSH, caffeine containing drinks affect TSH.
* If taking thyroid hormone replacement, leave off Levo for 24 hours before blood draw, if taking NDT or T3 then leave that off for 8-12 hours. Take after the blood draw. Taking your dose too close to the blood draw will give false high results, leaving any longer gap will give false low results.
I take my Levo in the early hours of the morning - somewhere between 3am and 6am. What I do is adjust the timing of my dose the day before, I delay taking it until 9am, I know I will be doing my test between 8.30 and 9am. So you could adjust the timing of yours for a day or two before your test. Just make sure you don't take 2 doses in 24 hours, e.g. say your test is on Wednesday morning. You could take Sunday night's dose on Monday morning, then Monday night's dose on Tuesday morning, blood test Wednesday morning followed by Tuesday night's dose. Then Wednesday night's dose take as normal.
When taking T3 in any form, either synthetic T3 or NDT, then general advice here is to leave 8-12 hours between last dose and blood draw. The advice about leaving 24 hours is for Levo only. Also, advice is to ensure we do the test under the same conditions every time. There is a circadian rhythm with TSH, FT4 and FT3 so there will be natural fluctuation as well, therefore to compare results accurately it's important that we always do the same.
Your results may not have varied, but as we are all different it doesn't mean that everyone's wont vary.
I’ve been reading the posts to get advice on best way to approach upcoming tests. I currently take 75mcg levo and one metavive 1 daily. I understand that I should take last dose of levo 24 hours prior to tests but are instructions for the metavive the same as NDT? I’m also slightly confused about the 8-12 hour timescale. If I take my metavive only once daily and same time in the morning as my levo what is the reason to take it 8-12 hours rather than 24 hours prior to tests like levo?
Metavive, although no hormone content is disclosed, you would treat the same as NDT for the purpose of testing, so last dose is 8-12 hours before test. The reason for this is because NDT has both T4 and T3, and it's the T3 that needs the 8-12 hour time gap because T3 starts to leave the blood after 12 hours so becomes undetectable in the test if left too long and you'd get a false low FT3 result. Those of us who use T3 or NDT change time of taking it the day before, if necessary, to give the correct time gap.
Thank you! According to my last test results my t3 was quite low and t4 reasonably high so I didn’t know whether to leave off the metavive for 24 hours also. My aim is to see if the Endo I’m seeing next week will prescribe t3 for me. I don’t like taking Levo as I am convinced it is responsible for my tummy issues.
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