Could someone with low FT3 do ok on Levothyroxine only?

Hi All,

I'm puzzled. I had a doc tell me that he thought I was having trouble converting. My FT3 is low (2.0; range 2.2 - 4.4) and has been for months. I'm also low-"normal" in FT4 (1.13; range .82 - 1.77). I was afraid to do the Synthroid from the many layers of horrible I've read about it, but now I wonder is there any truth to Synthroid, or is it wholly awful. I mean, if one has high or midrange FT4, would they take t3 only? So then, who can successfully use levothyroxine or any other t4 only drugs??

I met this doc while searching for a thyroid doc. So I didn't stay with him, and while I didn't take the Synthroid he'd given me, I still wonder, is there is evidence, or do you have experience, of low conversion and low FT3, low/"normal" FT4 and doing well on Synthroid only? Is that just absolutely unreasonable?

He's 81, old school, but I honestly don't think he meant any harm. Is there a theory out there that agrees with him? If I were truly a poor converter wouldn't my FT4 be a bit higher?

Thank you in advance.


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22 Replies

  • Your FT4 is just over mid-range, so not that low. Your FT3 is under-range. So, yes, you are a bad converter.

    I don't know about synthoid specifically, but lots of people do do well on T4 only. We bad converters are in the minority.

  • So when you say we bad converters are in the minority, you mean we wouldn't do well on straight t4 at all, bc we can't shift it into t3?

  • I think that is what GG means.

  • Exactly.

  • Get your Vit D, B12, folate and ferritin checked and post with ranges. They help the conversion so you are probably very low in them and need to supplement.

  • Hey there Silverfox7, I am high in B12, but low in everything else you mentioned, particularly ferritin (waiting to hear back about my full iron panel)...I've just been trying to learn the physiology of t3 and t4. I think I'm having a hard time accepting that medical practice at large is pumping t4 to he how can they do so in such large numbers and with a straight face! I was trying to see if maybe there was some sort of reason, but I'm finding there isn't.

  • We need minimum levels of Vit D, B12, folate and ferritin in order to convert T4 to T3, this holds true whether we are talking about any remaining natural production, synthetic or NDT. Vit D needs to be in the replete part of the range, ie over 75 and better around 100, b12 over 500 and up towards 1000 if you can manage it, folate mid range and ferritin over 70.

    My conversion issue was not as bad as yours but I had low b12 and folate with dire vit D levels. I followed supplement advice given by Seasidesusie and got them raised. Instead of 4.5/1 ratio mine is now 3.5/1 and a lot of remaining niggly aches and brain fog also disappeared. My Vit D is still poor so I may get to the ideal of 3/1 yet.

    You need to avoid the temptation to over exercise, cut too far back on the carbs and reduce calories too much as these all negatively impact on conversion and hormone levels

    If after fixing all of the above you are still not converting well there is the possibility of a genetic fault which means you need T3 only, the test isnt cheap so I would try and sort nutrients first.

  • Hi Phoenix605,

    I will def look up SeasideSusie's page. I've seen her ferritin protocol and was impressed, but I didn't see a vit D one, which I need bc I can't seem to get it up past 58. And I've been working on it for years... 😩 I have had much improvement using the vit d oil drops (I was told it better absorbs, and I went from 25 to now 60 in vit D).

    I was on t3 only (Cytomel) for a few weeks but I felt dried out, had high blood sugars, and unimproved. I will def try and get these minerals up and hope not to have to endure the tests required to warrant a t3 only regimine.

  • You can google the NICE vit D deficiency guidelines for your area. This will tell you the treatment options your GP should adhere to when giving loading doses. Even though you are no longer deficient you are still scraping the bottom and insufficient. Repeating the loading dose should help and if you are struggling to raise levels is very unlikely to over dose you. I have loaded twice so far and in the middle of the third attempt. You MUST get a blood test after as the body cannot get rid of excess unlike with the water soluble vits.

    Seaside Susie often points people in the direction of the vitd council website. They explain the need for co-factors (k2-mk7 and magnesium) which help ensure that calcium is directed to bones and teeth, not soft tissue) and the best forms to take.

    Vit D is fat soluble so how you take it is crucial. You are better off with an oil softgel rather than a tablet. I use a bottle of drops off amazon that has 2000iu a drop and also contains the K2-mk7 co-factor. It is olive oil based and not unpleasant. I also take my omega3 and evening primrose soft gels at the same time to make sure there is enough fat involved. Alternatively take it with the fatiest meal of the day

  • In MHO, I would shore up your Vits and minerals as described above, then increase your Levo a little (like 25mcg) and after about 3 weeks see if your T3 increases i.e. get another blood test. That was my problem. I boosted my Levo to about 150 mcg (which is high), my total T3 went to 132 ng/dL and I felt great! A lot of people do OK on Levo, it's just if you do not convert (T4 to T3) that you run into trouble. All advice given above is great but I want to add that you should get Selenium (via Brazil nuts if pos.). Selenium is the catalyst (enzyme) that precipitates the T4 to T3 conversion. You must look after your liver for conversion to take place = don't overdo alcohol. I don't mean give it up altogether, just don't overload your liver processing alcohol, it will be needed to do the conversion.

  • Thank you LAHs. I am trying to work in my mineral improvement. My iron is horrible. Selenium, is good and I eat Brazil nuts everyday. But it just seems so difficult if not impossible to use supplements to increase low minerals. I know it's best from foods but I'd have to eat copious amounts to get the levels I need.

    I wonder why so many people on Levo say they do so much better with t3 added?? 🤔🤔

    It's so frustrating because everyone is different so there's no template so to speak. But I agree and will heed your advice to get my minerals up and work hard to do it.

    I'm on Nature Throid, a very low starter dose, 3/4g. But keep wondering whether my fight to get NT and the hell it cost, was necessary.

    Thank you so much for your time and helps tremendously.


  • I was reluctant to take an iron supplement for years, I like to get metals from food rather than a pill because it is easier to overdose via a pill. I ate red meat for years and could not budge my iron level. About 6 months ago I broke down and bought a bottle of iron supplement pills, nothing fancy, just what my local supermarket had on it's shelf. I have to report that my energy has increased amazingly, give iron pills a try. Not too much to begin with, monitor your inside lower eyelid until it moves from white to pink or from pink to red. As soon as you hit red cut back on the iron dose (maybe once every other day). You will probably get constipated, this is the problem I have as a result of taking iron pills - my next problem to solve (lots of yogurt helps!). Anyway, you will get there, it's a time consuming problem.

  • Oh thank you! I didn't know about the eyelid test. I know pale/pink eyelids can indicate health concerns, but I didn't know about how it regarded iron. Thank you so much....I'll be sure to write that in my thyroid notebook....

  • Oh the constipation, have you tried (in sure you have) REACTED POWDER BISGLYCINATE Magnesium, in copious amounts?? Like 600-800mgs?? If you take it at night, you will get the effect in the morning; so if you've never tried this, I'd do it on a day you don't have to work. That amount is what used in the Emergency Room, as a laxative. It's the only mineral that I use that truly helps with constipation, fast heart rate, muscle cramps....

  • OK, I'll give that a try. Thx.

  • Oh, my pleasure...

    Please let me know how it goes.

    You will have relief the first use, but over many weeks you will notice it really helps overall calm.

    I don't know if you're in the states, but here is a link...

  • How I wished I had kept a diary but my thyroid journey started about 30 years ago and I was prescribed NDT and a book of charts to note my basal temperature. It worked for me and I found it easy to adjust my dose. Then a prolonged strike in Canada meant I was without medication to such an extent I asked to take Levo. But I was fine on that. I can't remember getting/seeing printouts but the hospital moved me onto a new scheme where they sent a kit to my doctor to take my blood and then send it back to them. I seem to remember at first they send results and usual comment no change in meds needed. I don't remember ever seeing a FT3 reading though but that's not to say they weren't testing.

    I was pretty good until I was told I was menopausal as I asked GP for an increase in meds which she gave me without doing bloods (!) and on the way out I said my periods had stopped 6 months ago so she brought me back and gave my a prescription for HRT which I took for 10 years when another GP stopped it as the new guidelines had been introduced. At the same time I went back to see the doctor who had first diagnosed me who was now in private practise so we went back to first principles and daily basal temperature and I was still ovulating!!!! So hindsight says I was undermedicated rather than menopausal but I knew my grandmother who had brought me up had no periods after 32 so an early 'menopause' did not worry me. But I still didn't know my T3 reading or its significance. But I did realise something was wrong but my GP now wassoneone I'd know as a student and seemed afraid of me and always asked if he was doing the right thing! I used this to my advantage and asked for more meds which helped a lot-he told me I could never over dose so he trusted me not to come to ant harm. Well I knew he was wrong but it put me in control and again I was doing quite well but the time came when I wasn't. I read a lot, my husband was a science based endocrinologist so had the books at home but had been left brain damaged in an accident so I no longer had his input but when he died I now understood about testing and and got the full works done by doctor Skinner who, unknown to me had asked my GP to add T3 to my Levo or put me on NDT-she refuse. She aslso wrote and complained to the GMC saying he never corresponded with her-a condition he had to follow so I refused to let he name me and also insisted that he always checked where the report was sent to. It was only when I received my notes after his death that I found this out! But the first time I asked here athyroid question she said she didn't know the answer so sent me to see an Endo who refused the ranges saying I didn't need them! I insisted the practice manager wrote as ask and it was then I realised I was low though FT3 high and I made a big step in my recovery joining this forum! I also wanted to go back on NDT as that was a stable time in my life. I found a new Endo who did loads of tests and I found my mineralsans most cuts were low. It again I didn't know optimal was the key. The Endo was pleased my FT3 was lifting so I asked if I would be better with T3 added and he refused as I was now halfway up the range and he thought it would keep going up. He was retiring though so I didn't know what would happen next plus they were struggling to replace him. I spent all my time reading posyszetc and began to realise the importance of optimal vitamins. My Vit D was creeping up as I had been given a booster dose and then the usual 800 iu Adcan but my calcium level was riding, folate wasubdersange and after 3-4 months treatment had just scaled in so I supplemented myself and after a year it was near the top so now I take the same dose every other day to keep it there and B12 wasn't brilliant so again supplement and by now had added others in or u had been on things from day 1. I had also learn about conversation and now knew that in later years that had become my problem but after 6 months I had righted that and was feeling good so at that point with all my supplementsas good as perfect I took the plunge to get some NDT and not looked back but I still maintain it's the correction of conversion that's done the trick and NDT I find easy than I was fine ding Levo. Had I not done that would Levo been a problem, I don't feel it would have been but the Endo was willing to monitor so I gave it a change. Sadly he was only there a year and the replacement wants me to stop it though he is more than happy with my bloods and says I know what I am doing! So hopefully I can keep taking it! Because of my experience I think it's something that should be addtressed rather than just throwing T3 at it as we need decent levels of the Fab Four anyway but it does take time to address if levels very low but over the years I've realised patience is necessary plus I did t take 6 months on extra supplements and then it suddenly made a change , it was gradual so I kept improving.

    So I think you should concentrate on addressing the conversation first than then see if you are still undermedicated or if you increase thyroid meds as well be prepared that you may have to drop it down a little as conversion improves. Thyroid problems affect the whole body so treating the whole body may be needed to mend it.

    Sorry it's a long reply but it's been a long journey to wellness as well.

  • have really been through it. I remembered you telling me that your late husband was an endo researcher. The irony that you have to spend your life essentially as an endo researcher via your thyroid care.

    I am trying to work on supplements and conversion, it I don't know if that means stop taking NDT while I do that? Otherwise, I'd have to go as I have been, and that's taking and titrating upward but slowly, on NDT, WHILE working on the conversion.

    The doc I'm with now is kinda weird, and believes in medical mediums (yeah, like how people read futures, he studies a guy who reads people's medical "future" diagnosis!! So basically a psychic! Weird!!!!) but he takes my insurance, worked with the publication of the second STTM, and wrote a chapter. So that's how I came to see him. I will stay at least for now because while I don't think he knows much about thyroid, he writes the prescription for Nature Throid and will run labs I ask for. So far.

    I called Mark Starr's (author of hypothyroidism 2, and also hypothyroid himself) office but he's not taking patients and is giving his partner all the new patients. The partner is a cardiologist who supposedly studied under Starr and follows his protocol. The office is expensive, doesn't take insurance, and is across the country (I live in Houston Texas and the office is in Phoenix Arizona) . So for now, I'm staying where I am, at least for two or three more visits.

    I've lowered my standards: I just need a doc who will do what I ask and order the labs and scrips I ask for without being a jerk about it. Oh and who preferably accepts my insurance!

    Yes I keep a notebook but don't be lsntotally unorganized. Can't find anything when I need to. And while I purchased some very nice mercury free thermometers, every single morning I wake up and go to the restroom, only to remember that I forgot to take my temp! Every day. I forgot this morning too. I think I will set an alarm to wake me just for that purpose - to take my temp. I'd even placed a flashlight and thermometer on my nightstand so I would just roll over and take my temp. And I still forget. Errrrrr!!!!

    Do you stil monitor by temp?

  • Yes still temperature! You can't tell if you have a. Oncerstion problem whilst on any form of T3 as only the FT3 reading is accurate so you can't compare FT3 with FT4. When you are on NTD FT4 can drop to halfway so it's the. Am bit that matters, it may or it may not so you can't compare. If you are already on NDT I would continue but get the Fab Four, B12, folate, ferritin and Vit D optimal as these 4 help to convert the T4 to T3 so if you do that and sit st tgat level for a while then hopefully you will feel good so I suppose you can then presume you have improved it but if you still don't feel good then you may have to go back to Levo and. Heck the readings.

  • Thank you...I have never taken straight Levo. I was given Synthroid samples, but never took them. NDT Nature Throid is my first thyroid medication.

    My Vit D (60) and ferritin (15) are low. B12 is high (1237). But I read that when b12 is high it could indicate an absorption issue?

    When on NDT the FT4 typically drops, so when people say , to be optimal, FT4 needs to be at half range, and FT3 should be in the upper third, does that apply when starting medications? So once on proper meds, you should expect FT4 to drop?

    When I go back to the doc I will ask for an infusion, assuming my full panel indicates needing it (saturation %, iron serum, tibc, and ferritin) If he refuses, I don't know what I will do.

  • Looking at Levo I've always understood that FT3 AND FT4 should be in the top third or even quarter i their respective ranges so I take it from that it means they can be different figures but working of where they are on the range persentage wise they should be about the same but once on a form of T3 the FT4 will fall as it's not needed as much.

  • Ahhh. Ok, so we use the current lab to navigate the meds. If the lab is beneath the top of the range we know to increase the meds. But once on sufficient meds the FT4 will drop.

    Thank u so much. Learning all I can.

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