Thyroid UK
82,758 members97,783 posts

How to take medication before Genova Thyroid Plus test?

I am going to do the Genova Thyroid Plus test privately. I am currently on 150mcg thyroxine and 10mcg liothyronine daily. Can you advise how I should take this medication prior to doing the test to get optimum results? (ie should I stop taking them and how long before testing).

Also, the same question for when I get my blood taken on the NHS; they only test T4 and TSH, never T3. Thank you.

9 Replies

Harebell, leave 24 hours been last thyroid dose and blood draw. TSH is highest early in the morning and before eating so early fasting tests (water only) are recommended if you hope to have your dose increased or are worried your TSH may be too low.


Thank you very much. I didn't know that it should be that long a gap from taking your meds. Wonder if that has been skewing my NHS results for years? My last result was TSH of 0.03 and T4 was 16. T4 is normally higher, about 19, but TSH has been very low for a while.


Harebell, It will have skewed TSH lower and FT4 higher than normal.


Interesting, thanks. So my T4 could actually be lower than I think it is. Would that indicate a reverse T3 problem?

I was wondering if I had reverse T3, and that's the main reason why I was going to do the Genova test.


Harebell, A large proportion of T4 converts to active T3 and a lower proportion converts to inactive rT3. rT3 is the body's brake on converting excessive amounts of T3. I don't think FT4 16 or 19 is indicative of high rT3, but neither does it exclude rT3 being high. If you're testing rT3 you may as well have an FT3:rT3 ratio test too.


Thanks so much for your advice.

If I do the Genova test and get FT3 and rT3 tested, I should be able to calculate the ratio myself (with the appropriate guidance!), would that be right?

Or can I get the FT3/rT3 ratio test done alone; who does that?


Harebell, You'll have to have FT3 and rT3 tested to work out the ratio. STTM has a calculator to help work out the ratio but some members have found it complicated.


I thought I'd seen advice somewhere before about how to do the ratio.

But I may have to be back again for advice then, if I may?! And I'm sure I'll have loads more questions as a result of the test.

So, with relatively low T4 currently, does it just look like I need more thyroxine and / or liothyronine?


Harebell, CC120 posted two threads about rT3 yesterday. The STTM link explains how to calculate FT3:rT3 ratio

I wouldn't call FT4 16 low, but if you want it higher you need more Levothyroxine. Liothyronine will lower FT4 and raise FT3.

1 like

You may also like...