Log in
Thyroid UK
91,839 members106,105 posts

24 Hour Urinary Thyroid Test

Can anyone help please? I'm on 75LT4 and 20LT3. I am due to see my endo soon and he will be carrying out blood tests. He prescribed 75/10 but my GP has let me increase my T3. The ratio is probably wrong, but I feel good. I have to make decision about when to take my T3 - endo was shocked that I omitted my morning dose at the last appointment ( I thought it was just sensible practice to avoid stupid peak levels ) The tests will happen at 10:00am

Anyway, for my own purposes, I am thinking of using the urinary FT4 and FT3 to guide my dosing decisions. Does any one have any experience/advice please? It is worth you knowing that if I don't agree with my endo, I will do exactly as I choose and use any prescribed meds to keep the costs down.

Thank you in advance.

4 Replies

AndiRiley I have done the Genova 24 hour urine thyroid test, once before starting T3 because serum tests showed my conversion was poor and the urine test confirmed this, and again 3 or 4 months after adding T3 to my Levo to see how the levels had changed.

I'm not sure what you want to know but I can tell you the urine test results bear little relation to the serum test results - for example my serum FT4 was way over the top of range, 28.5 (12-22), and my FT3 was 5.1 (3.1-6.8). The urine test showed FT4 only mid-range and FT3 below range.

When I retested after adding the T3 and lowering Levo, my urine test showed FT4 was down to one quarter way through range and FT3 was half way through range which is just about what I was expecting (and hoping for).

When doing the urine test it's very important that you follow the instructions exactly, making sure you start with an empty bladder at, say 8am Monday by discarding that urination, collecting everything else throughout the day, evening and during the night, and collecting your last urination at 8am on the Tuesday (obviously changing day/time to your won). You must not collect the 8am urination on the Monday, it must be discarded, and your last one must be 8am Tuesday. Also, take only the amount of thyroid meds you would normally take withn a 24 hour period. So if, say you take your 75mcg Levo and 20mcg T3 (in divided doses if that's what you do), you still take all your thyroid meds but no more than those amounts within that 24 hours, you adjust the timing if necessary. You are looking at what 24 hours' worth of meds goes into and is used by your cells, so exact meds are essential, as is the exact 24 hours of collecting urine.

Also make sure you still to the recommended intake of fluid, which I think is no more than 1.5 litres in the 24 hours.

Was there anything else you wanted to know?


Thank you SeasideSusie for your reply. Can you tell me how you feel/symptoms are now that your urine results are mid range. I have read that Urine levels correspond most closely to how the patient feels.

Your comparison of serum vs urine both before and after adding T3 and reducing T4 seem to me to indicate that your body is now "using" the hormones and I would guess you feel better?

I am becoming less and less impressed by the value of FT3 levels simply because we rarely get enough info about timing of dosing versus timing of test. It would have more value if there was a standardised way to do FT3 testing, eg - half way between doses ( if and only if, doses are equidistantly spaced ) With uneven dose timings and long over-night gaps - who knows what the average FT3 is; which is why I am investigating Urine testing.

Any thoughts?

1 like

Hi AndiRiley Yes, I agree about timing when on T3. I must say I'm not 100% sure what to do (for serum tests that is, you take your meds for urine test as I mentioned), but as T3 peaks around 4-6 hours after taking it then drops off, leaving it off for 24 hours doesn't seem right, there'd be very little left so I can't see how a serum test would be accurate in those circumstances.

I haven't actually had a serum test since starting T3 and what my thoughts are when I do have one is this. I take two doses - one early morning (probably when I get up for the loo about 3-5am, or maybe later about 7am), and one in the afternoon about 5pm. I will leave my levo off for 24 hours as is always recommended, but I will take my T3 at 5pm on the day before the blood draw but not take the early morning one on the day, I will take it after the blood draw. So that would be something like 16 hours as my surgery's first appointment is 9am, or if I do a fingerprick test at home I could do it earlier but it would still be about 14/15 hours. I still think that may be too long but I don't see how I can do it in any less time. But, I don't know if this is right, I'm just guessing. Proper official guidance from doctors who prescribe T3 would be good, but they don't seem to agree on much when it comes to thyroid anyway so you still wouldn't know if the advice would be correct.

By the way, my T3 is not NHS prescribed, my GP doesn't know I take it.

The urine tests certainly does show I am using the T3 (and it would be interesting to compare a urine test done at the same time as a serum test, but that's for another day).

When I first started T3 my dose was 6.25mcg and I lowered my Levo by 25mcg. I didn't notice anything. Some people know right away that something is happening, feel something, have more energy or whatever. I felt nothing. I increased after 2-3 weeks to 12.5mcg, same dose of Levo. Again, I felt nothing. But I seem to be the sort of person who never has a reaction to anything, whatever happens it seems to happen gradually.

Three months after adding T3 I began a supplement regime recommended by a holistic hormone specialist (tests showed adrenal and sex hormone problems). I can now say, 5 months after changing to that supplement regime and continuing on the same dose of Levo and T3, things feel better. I can't put my finger on what it is. Obviously the supplements have had an impact but I also think the supplements may have helped the thyroid hormones to work better, which is why I want to do another urine test to see if there's any difference. When I get those results then I will decide whether to increase the T3 to 18.75mcg - I want to because I think I can feel better than I am, but I want to make sure I need the T3 and not more time for the supplements to address the problems they're meant to. So more testing there.

I've concluded that it's a combination of adding T3 and supplements addressing the other problems (which I didn't know I had when I started T3).

It really is a minefield, the mind boggles at all this stuff!

1 like

I like your comment, "I think I can feel better than I am" Me too. Try explaining that to a GP or endo!

I think I probably will have to continue deliberately skewing the blood test results by not taking T3 for ages before my blood test. I know it means the results will not provide useful information, but it hopefully will mean that I will continue to get T3 prescribed ( and I can then decide how much to use ) I really would like to work "with" my endo, not work around him.


You may also like...