Hi
my daughter takes 100 mcg. levothyroxine and 25mcg. T3 at night before going to bed. I have just purchased a private blood test for her, can someone please advise when she should stop her medication before doing the blood test. I know levo. has to be stopped 24 hours before test but not sure about the T3.
She also takes Vitamin B6 to help with her PMT, should this be stopped before test as well.
Advice appreciated, Thank you.
I would take the blood around half way between doses, so if she takes it at night she could take the blood in the morning. If she wants to take the blood early morning just take her thyroid meds a little earlier in the evening. As long as you leave > six hours after levothyroxine it will make little difference to the result.
If you leave just 6 hours the fT4 result will be about 2% higher and if you leave 24 hours the fT4 result will be about 4.5% lower than the average 12 hour gap. These differences are similar to the limits of accuracy of the assays and individual variances from day to day and hour to hour.
Many thanks,
I always thought levo. had to be stopped 24 hours before blood testing, everyone seems to go by that on the forum.
jimh111 has different opinions on this subject compared to the rest of the forum.
Whatever you decide to do (I always go with the majority) keep notes on it and do your best to reproduce the same conditions every time you test. It means you can more readily compare results from one test to the next.
lucylocks
Last dose of T3 is recommended to 8-12 hours before test. So if her test is at, say 9am, then last dose of T3 should be between 9pm the night before and 1am.
As you say, it's recommended for last dose of Levo to be 24 hours before test.
Many thanks,
as she takes her T3 all in one dose, should stick to the one dose of 25 mcg. 8 to 12 hours before blood test or take half dose in the morning the day before and half in the evening.
Also will Vitamin B6 effect the results or is it just B Complex that needs to be stopped before testing ?
It's any supplement or medicine containing Biotin that is the problem. Vitamin B6 is not an issue, as far as I know.
The reason for avoiding Biotin before testing is described in these links :
healthunlocked.com/thyroidu......
healthunlocked.com/thyroidu...
If you are getting any testing done which is affected by iron e.g. an iron panel, serum iron, ferritin or a Full Blood Count , for example, it is a good idea to stop any iron supplements for 5 - 7 days before testing.
Lucylocks
Best to split dose of T3. I split mine into 2, some people split into 3.
As humanbean has mentioned, no need to leave B6 off, just take after the test on the day.
Many thanks,
do you mean split T3 before the test or she should be splitting it every day ?Also she suffers from insomnia, I have wonder if taking the full dose of T3 before bed could be causing it.
Split before the test. The rest of the time she can take it whichever way she prefers 
I take my last dose of T3 around 10pm when I am doing a test next day, I haven't found it affects my sleep, but we are all different. She could experiment with different ways of taking it and see if it makes a difference.
Thank you.
Stick to full T3 dose 8 to 12 hours before blood draw, that way you will be measuring fT3 about half way between doses. Since you lose a bit more T3 in the first 12 hours after a dose it will give a good indication of your average fT3.
Thank you SeasideSusie! I was needing that info also for my upcoming blood test, I had forgotten what was recommended on here!
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