Is this the last word on t3/t4 equivalence?

I have read various things about how much t3 equals how much t4 and have hedged my bets w the 3x-5x spectrum. The following paper asserts it at 1=3. I have had a bit of a google as it is an oldish paper and I was wondering if there has been any further discussion/research on this point.

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I read once that Dr M says 10mcg t3 = 50 levo but I can't find any evidence of that. I recently read elsewhere that it might be closer to 10 t3 = 20 t4 - ?

19 Replies

  • RLC labs state that T3 is equal to around 100mcg of levo and that's what I understood it to be when I began. I think it may be the 'effect' of T3 on our body, i.e. I may need less, some may need slightly more but those with Thyroid Hormone Resistance needs far more. Also some people feel fine on 100mcg of levo and others can take much larger doses. So I think it is how our body 'feels' on a particular dose is the best judge. That, of course, is only my opinion :) The aim of taking thyrod hormones is to relieve all clinical symptoms not, as doctors believe, getting the TSH in a range.

  • Thanks shaws. Sorry, how much t3 is equal to 100 levo? That chart doesn't have t3 on it.

    As you say the dose is whatever makes you feel well but I need to be able to calculate any change, however approximate, to have an idea of what more or less matches (or is higher or lower than) my previous dose if that makes sense.

    I ask because it seems like 15 t3 is too little and 20 is too much. Am really struggling to figure out what to do next.

  • Apologies - I will have another look.

    If you are trying to increase your dose, cut the tablet into 4.

    UK T3 is 20mcg. Other T3s are 25mcg. You can cut tablet into quarters and gradually add every couple of weeks a 1/4 until you feel well.

    I take my T3 but I've never queried the dose - I just have increased up to a certain point, then my body lets me know if I've gone a bit too far, and dropped to previous quantity and stayed there.

  • Thank you shaws. I think maybe now the thing to do is to take my levo at night and my t3 in the morning all at once. I was told that 50 levo and 15 t3 would be a dose reduction but 50 levo and 20 t3 feels like a drastic dose increase to me.

    I really struggle w raising t3 and never seem to feel 'well' so it's hard to know.

  • 20mcg T3 I think is around 75mcg levo. The Endo dropped my dose of levo to 75mcg and added 10mcg of T3. She then got nervous and Nurse phoned me at home due to blood test result and told me to stop T3. I said NO I am not (because the difference I felt was immense). So I was told to drop to 50mcg plus the 10mcg T3.

    Now, I please myself. :)

  • If I knew the correct amount to make me 'feel well' (ie please myself) I would do it too! :-)

    I never get there so I feel I need to make the most precise calculations I can make so at least I have somewhere to start from.

  • I have never understood those equivalence charts. Like Shaws points out, some need less, some much more, depending on our bodies' needs and taking into account possible thyroid hormone resistance. I need more NDT than most, it would seem, yet have no hyper symptoms and my FTs are well in range.

    So go by how you feel, especially if on NDT or T3 as that tends to suppress your TSH below 0, meaning you need to by symptoms rather than lab results.

  • I understand what you're saying. I'm trying to calculate a rough equivalent to my last dose, which did not make me feel well but was better than I feel now having raised my t3. I would like to find the closest equivalent and stick there for a while to see if the different ratio (more t3, less t4) is good for me or not. So this isn't about lab results, it's far too soon for that.

    I read a lot about adjusting dose according to symptoms but what I'm saying is that when I adjust my dose my symptoms are often mixed (hyper and hypo) and never reach the point of feeling 'well'.

    This is the issue I have w STTM, I can't just increase until I feel well as I just keep feeling unwell in different ways if that makes sense. It is a real pain in the @rse.

  • I know what you never gets any easier, does it? I just wish I could be of more help...!

  • Oh bless, thank you, it just takes longer for some of us. I am better supported than a lot of people here so it could be worse. x

  • This is from Thyroiduk. The first is a compounded dose. Look to the Cytomel (T3). So 200mcg T4 is equal to 50mcg T3.

  • Thanks shaws, this is the table I usually use myself. :-) So they are going for the 1=4 theory.

    The issue is that no one actually says why they believe their theory to be true (except in the paper above) so in the end we are left w rough estimates and guesses.

    I was hoping to figure out, on the basis of evidence, if my meds adjustment (from alternating 75/100 levo/10 t3 to 50/15 to 50/20) is a higher dose, lower dose or the same dose.

    Otherwise I have to go back to my previous dose, which didn't make me feel well but was not quite so crushingly awful as now. So for years I've been trying to find the right dose of the right meds but I just keep going back and forth as above.

  • The trouble is the number is variable. T3 of course goes in direct, but T4 has to be converted to T3 and people vary as to their ability to do this for a given T4 dose. Roughly 5-6/1 is the average but only the average. According to your individual ability to convert, the numbers will vary.

  • Thank you diogenes, that makes perfect sense. I had been thinking it was something to do w the t3 but of course, how can one make a direct comparison if there is no fixed response to t4? If I am understanding correctly - ?

  • If you are starting NDT start low and build up over a few weeks. A straight swap will not work unless you are already taking some form of T3.

  • Thanks, no, just trying to adjust my t3.

  • Any sugar intake will effect some of your simptoms. I.e. Hot /cold. Energy /crash. Etc better to remove altogether while you get balanced. Best of luck.

  • Ridha Arem says 1 unit T3 = 4 units T4. But it's not that simple. My full replacement dose of T3 was about half of my theoretical full-replacement dose of T4. And I have found T3 seems to have a "smoother" effect on my system than T4. The bottom line seems to be that one has to do a lot of experimentation to find best dosage, whereas many allopathic docs think finding the right dose is simple (NOT!).

  • Yes, not simple at all. I know there is some variability, just trying to calculate how to raise my t3 and lower t4 in proportion to each other and the difference between 3x and 5x is quite a lot! Don't want to overmedicate and feel hyper but trying not to go hypo either. Last time I went very hypo I lost a lot of hair.

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