For those who take MP/Eltroxin:
People report that strength changes depending on the mix of pills - how do you compare the strength of 2x25mcg v. 1x50mcg and 2x50mcg v 1x100mcg?
Is there noticeable difference and, if so, which is stronger, in your experience?
They are supposed to be the potency given on the pill packaging within a 10% allowable variation. Eltroxin is the reference drug so all others should match up with Eltroxin. However, this does not necessarily account for individual variation in the rate of absorption due to fillers from different formulations.
I found many years ago that 1x100 mcg was different to 4x25 mcg both Mercury Pharmacy. Although there is a tolerance if doesn't mean that each in the range is anywhere near the same so always stick to the same brand and if you can get all your dose in the same amount so 25's would mean that you can do multiples though not all brands so 25's so may need to split 50's
Thank you. In what way were they different? I'm taking 100+50mcg now but if I change to 100+2x25mcg will it feel stronger or weaker?
It depends as you can't say every 25 brand will be under strength as some brands will also be over strength. It's a case of try it and see.
Sybilla14,
Some makes seem to use different formulations according to dosage.
That is, typically, have more excipients in the lower dosages - to avoid having low dose pills that are tiny and high dose pills that are huge.
There is a testing process where healthy volunteers take 600 micrograms of levothyroxine in however many tablets that needs. And see if it has the same effect as six 100 microgram tablets.
Think I'm on the verge of what my GP can take 😉 He is very sceptical about the dosing in tablets and half believed me when I was having issues with Actavis tablets. I'm starting to get well on 100+50 though my gp thinks I'm taking 100+25. I've open repeat prescriptions available to order for 100mcg as 100, as 50 and as 25 my GP told me to just use the 25mcg but I had left over 50mcg at home and worry that if I swap to 2x25mcg I may end up undoing where I got to so far. If I order the 50mcg he may refuse to process it. I may need to go in and explain myself🙂 It's all so complicated!!
PS I seem to be sensitive to small dose changes and makes.
I am back on Eltroxin and find they are stronger than the generic Mercury Pharma I was on before. I take a little less.
Karen
Thanks Karen. As I'm on 100+50 both eltroxin and I expect 2x25mcg of MP generic Levo would be less potent. You have, kind of, confirmed that. Out of interest what dose were you on before and what do you find works with eltroxin?
I understand that MercuryPharma only make one tablet and just market it as two eg Eltroxin and levothyroxine.
Well, I have had both and find them very different although get on with them both.
Karen
I have been on 175mcg MP thyroxine a few years ago but, recently, before I was on Eltroxin I took 150mcg. At present I am alternating between 150mcg and 125mcg - breaking a 50mcg tablet in half. I will monitor it as sometimes I feel I need more in Winter.
Karen
A few years ago there was a discussion on how much was in various tablets of levo and it came out that the MercuryPharma tablet had 28mg per tablet but listed as 25mg, this I believe is why I became ill when I tried another brand I was having much less each day than while on MercuryPharma.
Starfish123,
The difference was due to how that information was presented.
ALL 25 microgram levothyroxine tablets (at least in the UK) should contain as nearly as possible exactly 25 micrograms of levothyroxine sodium when measured as anhydrous levothyroxone sodium. This is the ONLY official way of measuring dosage in a tablet.
However, if they actually tip in hydrated levothyroxine sodium (that would be the pentahydrate, I think), that could mean they have to weigh out 28 micrograms per tablet. If you took the 28 micrograms of hydrated levothyroxine sodium in one tablet and dried it out so that it lost all its water content, you would end up with 25 micograms of anhydrous levothyroxine sodium.
Effectively they were saying: "This tablet contains the equivalent of 25 micrograms of anhydrous levothyroxine sodium and, in order to achieve that, we put in 28 micrograms of levothyroxine pentahydrate."
[Some years ago, I believe that one make of liquid levothyroxine that is no longer available actually made the mistake of measuring 25 micrograms of hydrated levothyroxine sodium. This resulted in a product that was around 10% sub-potent. However, that is my interpretation of the evidence and I could be wrong.]
Helvella,
You could well be right I just know I was increased up on MercuryPharma and then was prescribed another brand and reacted very badly, like I was being given less. I got the info from another site and they were adamant there was 28mg in MercuryPharma compared to 25mg in all the other tablets.
I know I’m not the only one that felt a decrease after trying another brand but it could just be psychological.
Starfish123,
Not for one moment do I question what you felt - that is your experience. There are all sorts of possible reasons for this and it certainly doesn't need you taking on the "psychological" tag! 
I have explained what I believe.
I cannot understand what rationale there could be for stuffing an extra 3 micrograms of levothyroxine into Mercury Pharma tablets. Not why the company would do it, nor why it would be allowed (or missed!).
Hi Hellvela. Thank you for your responses.
If it isn't the actual amount of the active ingredient (i.e. Levo) which calls for the potency tolerance range (here I mean the over/under % which is acceptable for a tablet) then is it just the excipients mix, which impacts on the potency by influencing absorption? I assumed that these tolerance levels were there to allow some slippage for the manufacturers such as the active ingredient is not uniformly distributed within the batch, etc. If it's to do with absorption alone then I think that these tolerance levels are misleading at best.
You may remember my experience a few months ago (you responded to me at the time) when I was not very well on the 100mcg actavis, which led me to mess around with reducing my doses for weeks. My TSH was 0.08 and my ft4 over range. I've been on eltroxin 100+50 for nearly 6 weeks, my TSH was 1.04 on 125mcg. Do you think there was something in the actavis, which may have accelerated the absorption for me? I'm struggling to explain why I appeared overdosed on 100mcg then but getting well on 150mcg now. Don't think there is anything slowing my absorption of eltroxin Levo.
What would your thoughts be on this, please?
Sybilla14,
My thoughts are very simple: We do not understand all the factors.
The testing of levothyroxine absorption is largely by giving healthy people (likely mostly young adults) 600 micrograms of levothyroxine and taking blood samples in the hours thereafter.
If the pattern of test results is similar to that of the reference product (Eltroxin in the UK), then they are accepted as of equal potency.
They do not test in unhealthy adults. Or children.
It could be the excipients. It could be the extreme fine grain structure of the levothyroxine ingredients. It could be the distribution within tablets.
The precise pattern of absorption could be important - a steeper rise in T4 in the blood could have effects that do not occur when it rises more slowly.
Bear in mind that we have mechanisms for getting rid of T4 by sulphation. Perhaps this mechanism gives a false impression of absorption profiles?
I end up feel more and more ignorant.
Ignorant you're certainly not!! Thank you again.
It really is so frustrating that there are no answers available to us. Such a common condition (synthroid is apparently the most commonly prescribed medicine in the US) yet so trivialised and so little effort to research it and offer solutions. My GP told me I'm an enigma as the more data and observations I collect on myself in an attempt to find patterns the more unclear everything gets😉
Appreciate your help.
Starfish123,
You have reported me for abuse.
I supported you in reporting your own experience.
I absolutely believe that variations between tablets (makes, dosages and even batches) can affect us - and sometimes very significantly.
There is no need whatsoever to let anyone suggest that these effects are psychological. I do not suggest that. I am supporting you in rejecting the "psychological" tag.
I think in anything thyroid related then being consistent is most important so what ever brand you take stick with it unless the fillers are an issue and then titrate your dose according to your needs
Are Mercury Pharma and Aristo the same? 
Mercury Pharma Levo availability
Eltroxin & Mercury Pharma 100 mcg shortage
Any problems with Mercury Pharma Levo?
Eltroxin - Advanz. Pharma 
