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When to take meds around blood work?
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When to take meds around blood work?

Does it make a difference if your take your thyroid med before going into to get blood work done or do you get more accurate results if blood work is done before morning medication is taken?
My Dr. has always advised me to go in for work up several hours after taking my Levo and Cyto but I have  feeling that this may not be correct for me.
My results keep showing me within the normal range but I'm experiencing very definite symptoms of  needing to (I think) increase my thyroid medication.
Help!
Any ideas?
K.
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213044_tn?1236531060
You should have bloodwork done early in the day before taking your thyroid meds.

Your T4 is elevated by 20% the first four hours after taking Levothyroxine.

Doctors almost always say it doesn't make any difference.
A gal who used to process bloodtests says it does matter.

Your TSH is also slightly higher in the morning, if that matters. A bit of trivia. Due to it's natural cycle, the TSH is highest before waking and then slowly drops through the day. I'm not talking a huge difference, but it's a fact that is interesting.
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Avatar_f_tn
How would they know if the meds are working if your not on them when you have your bloodwork done?
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213044_tn?1236531060
The med is in your system 24 hours a day. There is a spike in your T4 for a few hours after you take your med. If you are taking a T4/T3 combo, then your T3 will spike as well, I would guess.

It's better to have the bloodwork done before or after the spike, not during the spike. I don't imagine early morning would be much different that in the afternoon.

Just as it is with taking your medication, consistency is desireable. If afternoons work better, try to get the draws around the same time each time. If you can't be consistant, you can't. If you can, it is better.

I've had bloodwork done at all different times. Sometimes you don't have a choice.
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314892_tn?1264627503
As AR said, the free t4 is affected if meds are taken before the blood draw for TSH, freet4 and freet3.

If you are taking t3 and t3 meds, the TSH will be accurate, but the t3/4 will be falsly elevated due to the spike from the meds.

I would personally, do the blood draw as eraly in the morning as possible, fasting so you could then pop the pills right after on an empty stomach.

What are your levels from recent testing?

(I am that gal, by the way!)
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Avatar_f_tn
My levels from testing at the end of May were as following (this was going in an hour AFTER taking meds):

TSH # - 0.51
reference interval - 0.45 - 4.50

T3 non dialisis  - 3.5 (lab range 2.0 - 4.8)
T4 - 7.3 (lab range 4.5-12.5)
Total T3 - 150 (lab range 80 - 200)

***They appear normal, but I'm horribly "off."  I'm exhausted, can't concentrate, and spotting between periods.***  

I am presently taking 25 mcg of Levothyroxine twice a day (50 mgc total daily) and 5 mcg of Cytomel twice daily (10 mcg total daily).  I really feel like my meds are too low but I'm having difficulty getting my Dr. to agree because my levels are always within "normal range."
Could the timing of taking my meds before the blood draw cause such a discrepancy?  
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314892_tn?1264627503
The TSH is accurate no matter when you took the meds.

The t3 and t4 are likely falsly elevated by about 20% because of the spike in your system from taking them. Do some math (lol) and take 20% off of the t3 and t4 values and see what you get. You may be near the bottom of the range after doing the calculation.
(Mind you, this minus 20% is just my idea to get a sense of where your levels whould have been had you not taken the meds before the blood draw. It is not exact.)
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