T3 compared to Free T3

Hi, can someone answer a query I have please? If my FreeT3 level is 6.52 but my reverse T3 is 30, does this mean I'm not getting enough T3 in my body? I'm taking liothyronine 60mgs per day

(T4 total is 95.6 and Free T4 is19.87)

Thank you

17 Replies


How long have you been taking 60mcgs? Could you please post your results with the ranges and can you confirm that you are not taking Levothyroxine in addition to Liothyronine?

Hi Clutter

Really sorry to waste your time, I've just realised in my permanently confused state that I think I might've been taking levothyroxine and liothyronine at the time of my blood tests a few months ago - think I was on 100 Levo and 20 T3?

I'm currently taking 60mgs of liothyronine on it's own which I take going to bed and don't have any trouble sleeping - just trouble waking up! I'm going to the endo end of Aug so will continue on this until I see him as it will be interesting to see what the changes are in the levels? Another thing I've noticed though is I don't have any trouble jumping up in big steps with my T3 meds (20mgs at a time) even though I read a lot of times that you should increase slowly?


It was high rT3 and FT4 which made me suspect you were taking Levothyroxine. You wouldn't have either taking T3 only.

You should increase slowly to avoid having overmedication symptoms and overshooting FT3 range. The people who advise taking it slowly do so because they found the effects unpleasant when they increased dose too quickly.

Thanks Clutter, I know you know what you're talking about so I appreciate your input, however I don't get any unpleasant side effects from increasing my dose in big jumps which is what confuses me?


Not having unpleasant symptoms isn't a problem. Just count your blessings :)

will do :-)

Your FT3 is fine given your T3 dosage. You must have some working thyroid left as your FT4 is also very good. Of course you may be taking T4 as well which you haven't said. Wouldn't worry about reverse T3 - its only a "drain" to remove extra unwanted T4.

Thanks for replying diogenes. As per my reply to Clutter I've realised that I was actually on T4 and T3 at the time of my blood tests! I was just looking back at them and wondered about the Free and Reverse T3 and if it was a bad thing? Sorry about that!

Revsie - those results were from a year ago, they could be very different now.

There are other reasons for high rT3 eg chronic illness/infection/inflammation, very low calorie diet, stress, some medications can cause it.

The best test to see if T3 is getting to the cells, rather than a snapshot in a blood test, is a urine thyroid test.

The T3 in the urine comes from the blood! A urine test may be useful in giving an approximation of T3 levels over 24 hours but it cannot show whether T3 is getting into the cells. (All T3 comes from the cells, either thyroid or peripheral cells via diodinase).

I don't know who started this idea of urine T3 telling you it measures the amount of T3 getting into the cells but it's a myth that has perpetuated over the years. Pehaps they had a sense of humour and were taking the p***.

The urine test definitely tells a different story than the blood test. When a blood test tells you that your FT3 is 55% through it's range and a urine test shows that your T3 is below range, in a minus figure, and you have so many symptoms, then you know something is wrong. Then adding T3 and reducing Levo shows your urine T3 has increased to 50% through the range, along with improvement in symptoms, then that is proof enough in my experience that it's measuring something.

I agree to some extent. It is quite possible that the kidneys filter T3 (and other substances) in such a way that the urine T3 level reflects thyroid status. It is up to the companies marketing the test to prove this. What I think happens is that lots of patients with symptoms do a urine test and some find their urine T3 low and of course they respond to taking liothyronine, as would similar patients whose urine test shows they are OK. It is also likely that if healthy subjects took the urine test some would show up as low and if they took liothyroine it would make the thyrotoxic. i.e. there is no evidence to show the urine test is better at diagnosing and does not throw up false positives. ThyroidUK started a trial but unfortunately were unable to recruit sufficient subjects (controls) to carry on.

I'm not doubting the urine test has uses, it's just the claim that it shows what is happening in the cells - T3 gets into the urine from the blood via the kidneys. The assertion the urine test shows what is happening in the cells is bad science and endocrinologists will use this to ridicule patients and thyriod support groups.

I've never seen it recommended for diagnosing but I've seen it said that it is not useful in diagnosing but is useful in showing what is happening with T3, which has been my experience.

When I showed my practitioner my results she explained it that a urine tests shows what's happening 'downstream' - showing metabolites passed in urine.

'downsteam' Ha, ha! It's just possible that the kidneys play a role in T3 homeostasis and hold onto it when there is low activity and so reflect the level of activity in the rest of the body. This would tend to conflict with the validation of urine tests which is based on them being in step with blood tests. The other complication is that a lot of thyroid hormone is eliminated in the faeces. I dislike the claim that it shows what is happening in the cells, I've never seen any evidence to suggest this. It is just possible that it reflects hormone activity, theoretically, but I don't think this is likely. It's up to the companies selling the test to sponsor an independant study.

Personally I don't need any further evidence than I already have. My urine test showed a minus result for T3 the first time despite the blood test showing it to be 55% through range. Adding T3 and retesting urine showed it 42% through range and improved symptoms, with further improvements showing in the next urine test at 50% after a raise in T3 dose, then staying stable on that same dose at the next test. No further testing needed, I have the evidence that I need.

The proof of the pudding is in the eating so they say, I have proof enough regardless of what that practitioner said and without an independent study being carried out.

Apologies Revsie that your thread has been sidetracked. There's no further need for this particular part of the discussion to be continued.

As I noted, it could theoretically be useful but the evidence is you get false positives ncbi.nlm.nih.gov/pubmed/182... . In particular the second patient 'She had no complaints, and physical examination was unremarkable'. Urine T3 can be low in some patients who are suffering symptoms and also low in people who are hunky-dory.

I accept we should discontinue this discussion.

Hi SeasideSusie, yes I realised my error which is why I've apologised for wasting people's time. As I was looking over my history trying to see a pattern or some indications of what certain things could mean, I suddenly noticed (and unnecessarily as it turns out) got worried that the reverse T3 was so high and thought it was something I'd missed last time that could indicate something important? I incorrectly gave the dosage I was on now instead of then so tried to correct it? Apologies once again.

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