If you are taking Synthroid or any other T4-only med within 8 hours before a blood test, it will falsely elevate the result of your FreeT4 test, but won't affect Total T4, Free T3, Total T3, T3 Uptake or TSH.
If you are taking Armour (or any combination of T3 and T4) within 8 hours before a blood test, it will falsely elevate the result of your Free T3 and Free T4, but shouldn't have an effect on Total T3, Total T4, T3 Uptake, or TSH.
If you are taking Cytomel within 8 hours before a blood test, it will falsely elevate the result of your FreeT3 test, but not Total T3, Free T4, Total T4, T3 Uptake or TSH.
So... If your doctor doesn't take those above-normal spikes in T hormones into account, and if he doses according to the FTs and not just TSH, he might reduce your dose based on the false elevations.
I take my Armour after the blood draw, even though my own MD wouldn't reduce a dose based only on labs without considering clinical signs and symptoms.
Hi why dont our docs tell us to have the blood drawn before we take our meds (levo in my case)? Does it really make a big difference? Im due to have my blood done after the 20th Jan wondering whether l should have my levo afterwards just out of curiosity but can it really make that much difference? After all we have a build up of levo l believe it takes 9 days for levo your taking to leave the body so l cant understand how just having 1 pill alittle later than normal can make a big difference? Sorry if l confused anyone lol
The T4 only meds don't make that much difference, but some people wait and take it after the stick anyway just to be sure. (Because like you said, they are not fast acting and build up in the blood stream slowly).
The T3 meds can make a big differene (in some of the test).
I would be sure to have the blood drawn early in the day (no matte what med you are on & even for those NOT on thyroid meds, early is best to be stuck for thyroid test).
25 years feeling worse every year on Synthroid & 13 months feel good on Armour Thyroid.
My IM that prescribed Levo for me and just started me on it.. didn't tell me not to take it on the day of blood work, but she tell me to take it a 9am and set my blood work follow ups at 8 am. I took this to mean. No meds before the test.
Why? Well as Midwest stated it will cause and artificial spike in blood concentration levels. You want to see what your retained blood concentrations are when it is time for your next dose. This will tell you if your are optimal through out the 24 hr period.. not just after the meds are taken. I can tell on my seventh day of meds that my body is adjusting and that the dose is still low, I was certain I wouldn't be able to tell; but I know my body's signs well these days. My hypoT signs are still here and while initially the supplement would make my constant throat ache and other symptoms go away for a few hours after taking my meds.. now they do not change. The beginning of the road to change. I am hoping that things will get optimized quickly, but I expect it to take a while. So in the mean time I plan on making sure that I schedule 8 am blood work draws and remain in a fasting state 'til afterward to ensure I am getting my base line low blood concentrations are what I am adjusting too.
If we learn by our mistakes, I am working on one hell of an education.