I'm hypothyroid and I'm experimenting with switching doses at the moment. I'm going from 100T4 to 125T4 and 10T3 to 15T3 and I want to keep going up if my changes are still too low and minimise my suffering on too low a dose. However, I don't want to move on up if I haven't waited long enough for the hormones to fully (at least 80%?) to kick in, because I could end up overdosing down the track. It happened many times before.
I know ideally I should wait for 6- 8 weeks, but I think you can make a judgement much sooner, especially with T3, to make the process more efficient and minimise suffering on too low (or too high) a dose.
I know I can use a half life calculator for stepping DOWN the dose, e.g. If I want to halve T3, I could stop taking all T3 for the duration of 1 day (or 2.5 days depending on which literature you take T3 half life from).
I'm less sure about switching up. Anecdotally, for me, most of the changes when increasing T3 seem to occur within the first 3-5 days (10 days max) and T4 ~7-10 days (20 days max).
Does anyone know of a good rule of thumb for within what minimum number of days, say 80% of the changes occur for each T4 and T3 independently being increased?
E.g. I switch 125T4 to 150T4 (keeping the same 10T3). Would a week of waiting suffice (or 2 or 4)? Same example if I keep with 125T4, but change 10T3 to 15T3. 3 days enough?
Just to give an illustration, what I heard is TSH takes 8 weeks to adjust, but the body takes 3-4 weeks. My previous functional doc said to give any dose (T3 and/or T4) 4 weeks and then get bloods and record symptoms. I've personally felt that most changes would be largely complete by 3 weeks of changing T4 and 10 days max with T3. BUT I just want to someone to corroborate my story and possibly justify it with logic and perhaps medical research?
Written by
ak_83
To view profiles and participate in discussions please or .
Frustrating as I know it is I would always stick to the 6-8 week period to give your body time to adjust. Its is tedious I know -I remember it all too well but this is a case of the tortoise winning the race not the hare. I found changing the doses earlier than this ended up confusing the picture and in the end had to start agsin so it actually took longer. There is no quick route to finding your optimal dose and combination. Slow methodical, keeping a careful record wins hands down. Sorry!
There must at least be a short circuit, such as if I'm feeling more hypo with each day or the other way around, then change if it is a consistent trend for several days?
I was watching a video of a talk Dr Paul Jenkins made to The Thyroid Trust and he said that given the short half life of T3, you know where you are with it pretty quickly as a patient. He didn’t say “provided that you don’t change anything else”, but I think that was likely implied!
I have no science for you and also did a bit of Googling recently and agree that 8 weeks for TSH to stabilise for a blood test is what my research suggested.
On the other hand, like you, I’ve never been surprised by a dose change late in the change window. I know whether it is right or not after about 10 days. Obviously this doesn’t rule out the possibility that I will be surprised in the future on week 5 or something and I certainly hear that very often from people who have been around and experimenting for longer than I have. And also from one of my favourite posters who let impatience get on her own way inn the past with this and previously held my view.
I think - given how different we all are with dosages and what meds work - on the one hand it is not unreasonable to think that some of us might adjust faster than others; on the other, the science, GPs and the patients seem to be mostly in agreement about the 6-8 weeks malarkey, which is unusual!
I am a deeply impatient person so all this messing around and waiting (I mean, I might get hit by a bus?) does my head in, particularly when I feel that, in the words of one of my favourite songs “I know what I know”!
Anyway, I guess I haven’t really helped in any practical sense, but at least you know you are not alone. If I didn’t have an NHS endo to keep happy, I would have changed this dose 3 weeks ago and I only hit the 6 week marker yesterday! And it still doesn’t feel right, so it is confirming my view that “I know how I feel!” I test next week so I’m curious to see whether the numbers back me up or not...
Expand? The idea is to optimise the path to optimal dose.
If I start with 100T4 and take 8 weeks, before increasing to 105, then 8 weeks again, and so on, but it turns out my ideal dose is actually 200, then 20 x 8 = 160 weeks, which is 3 years! Then you have T3 combos too. I might start with 100T4 and 5T3, but there are combos like 125T4 & 10T3 or 150T4 & 5T3. So to try it all to get an optimal combo might take 5-10 years if I waited 8 weeks before any change. This just isn't feasible. Nobody (definitely not me) has such a long time time horizon for experimentation and potential misery!
Some shortcuts and rules of thumbs need to be in place in order not to go mad. At the same time these should not compromise the experiment in a major way.
I'm a 72kg male. I started on 100T4,but it seemed way too low, so I'm now on 125T4 as someone amswered my previous post with an ideal amount of 125T4 & 7.5T3 as being ideal for a 70kg person and that takes absorption losses into account. At the moment 125T4 & 10T3 seems too low, but it's been only a week.
Yes, of course I check my labs. My endo got me to 200T4 (they don't recognise T3 in New Zealand as official treatment) and said according to TSH and FT4 I'm optimal and that's the end of his engagement. I was seeing a functional doc after that... Trouble is FT3 isn't definitive for me as I quite quickly start to feel adrenal exhastion (different tiredness to hypo) even before hitting 75% of the range (and they say you should get to 100% or even a little higher). Hence I'm relying on how I feel even more than the labs. Of course, I still test, but I'm weary of FT3.
Yes it can be very difficult ... have you had any potential adrenal issues checked btw. And NZ is a harsh place for those failed by T4 medication!
You really will keep going round in circles at this rate. Unless you provide a fuller picture of results with a progressive description combined with symptoms/symptom relief and give sufficient time between changes, imo, you won’t be able to be confident of ok interpreting the changes to work towards an optimal solution. And difficult for others to comment usefully.
Fundamentally I would suggest as others have a slow approach from a baseline start & at every stage take into account full TFTs results. A common wail from self-medication experiences while seeking to keep one’s GP “happy” is the time it takes for TFTs to adjust & settle & yes, even from T3 reduction ... there seems to be a lag of several weeks for levels to settle even if symptoms react more swiftly. If you try & do this by foreshortening dosage either up or down steering only by symptoms and short periods between adjustments you are very likely to find that frustrating.
My thoughts here are not specifically aimed at you but expressed more generically because of the advice that T4 medication can be pushed to the top of range in the hope that it raises FT3 sufficiently by peripheral conversion so as to relieve hypo symptoms. But recent research findings (see right below) question the advisability of that to my thinking.
I assume you are T4 tolerant and began on T4 monotherapy. And I hope you have already investigated key vitamin & mineral levels with appropriate tests to ensure no confusion or misinterpretation of symptoms.
Hopefully you have a historic baseline somewhere near the start of T4 monotherapy to track dose against full TFTs to give some idea of conversion effectiveness and a memory of any symptomatic effects. And likewise to however far you got with T4 monotherapy before realising this is not effective for you. Going to a high T4 dose & top of FT4 range has recently been identified as not a good move contrary to current thinking.
And some reckon anyway that for “partial converters” there comes a point in piling on T4 towards top of range where ironically it pulls down FT3.
Following here a sort of idealistic further steps ...
Obviously, with T4 mono not proving effective you should have in the full TFTs at every stage some idea of the proportional position in range of FT4 & FT3. Since FT4 mono wasn’t working effectively I assume that in FT3 being still relatively low below mid-range, in introducing T3 gradually (10mcg) at the same time you would initially reduce T4 by say 4:1. so that it no longer is at top of range
This would probably be the first of two times to adjust both T4 & T3 assuming FT4 is at or very close to top of range.
Again, after a further 6 weeks FT4 having had time to subside to its new lower level and T3 having raised FT3 slightly you would retest & reconsider symptoms and if still clearly hypo,
& FT4 still above 2/3 in range repeat the lower T4/increase T3 to adjust FT4 down another 40mcg & FT3 up 10mcg. Split the T3 dose and for both
Meds observe best practise re timing in relation to coffee/food/ other meds or vits & mins. supplements ... ESP iron.
Assuming again on T4 mono you got to at or v close to FT4 top of range on say 200 mcg T4, at that point you would be on 120 mcg T4 & 20 mcg T3.
If then still clearly hypo & no more than say approx halfway in FT3 range a slight increase in T3 (no more than 10 mcg) ... and yes, be patient, having split T3 meds into at least two portions give it 6 weeks and retest & reconsider symptoms. Take the retests say at least 6 hrs after your last T3 dose. Assuming FT3 now moving above halfway & still hypo symptomatic, if FT4 is still above 2/3 in range you might consider a slight reduction of say 20-25 mcg, follow the same procedure and only then consider a further T3 upward 10 mcg increase.
Now on 30 mcg T3, if another increase looks needed after a further 6 weeks increase another 10 mcg T3 always take both tft results and symptoms into account. While we each have our individual sweet spots (& set points) where we feel well in or even slightly above range for FT3 for some approaches or reaches the potential for becoming hyper. So as you raise FT3 well above 2/3 of range look for any change from hypo to hyper symptoms. Not necessarily very obvious but giving 6 weeks between even upward gradual T3 doses hopefully makes it easier to avoid going hyper for managing coming back down from there is apparently even more of a challenge. But if in that situation, again unless obviously hyper with substantial indicative symptoms requiring a sharp downward adjustment reduce gradually with a 4-6 week interval.
Re my comments about where in ranges & esp avoiding high doses/top or near top of FT4 if not already aware then regarding cardio health you might find this interesting!
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.
Should I increase my T4 or stop T3
T4 and T3 combo, timing of doses advice please
Results and help with T3/T4 dosing, please!
T4 levels in relation to T3 dose
Dr changed t3/t4 dose? How do i do it? 
