# TSH peak in relation to timing of taking thyroid hormone??



## Julied1071 (Mar 31, 2017)

I cannot remember where I read it, posted by an admin., TSH level is different depending on what time a day you have a lab draw. What time of day does tsh peak? Synthroid for instance has a long half-life. Does our Tsh stay constant if we are taking thyroid hormone?


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## joplin1975 (Jul 21, 2011)

Our TSH never stays constant. There are a number of variables which effect TSH...you activity levels, when you take your meds, if you are sick, etc etc etc. Which is why TSH should be used as a diagnostic test only.

I have said for a long time that TSH is not effected by the timing of t4 meds, but it is impacted by the timing of t3 or t4/t3 meds. And then I had to change the time of my blood draw from early mornings to late afternoons...and both my TSH and free t4 were impacted. So I'm eating my words a bit.

Basically, the closer to the time you take your meds, the lower your TSH and the higher your free t4 and free t3 will likely be. Conversely, the more time between meds and the blood draw, the higher the TSH and lower free t4 and free t3. BUT, I wouldn't expect MAJOR changes. As you noted, synthroid has a long half life. So your results will be in the same ball park...but there will be a difference. Its up to you and your doctor whether that difference really matters.


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## Lovlkn (Dec 20, 2009)

I understand it to peak in the morning,


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