weight to ratio of Levothyroxine

[5219]

hi can you tell me how much Levothyroxine I should be on for my weight please as I have been told by a thyroid group I belong too that I’m on too low a dose and not optimal. I also have constant aches and pains. I weigh 95.80kg and at the moment I take 75mcg of Levothyroxine and 10mcg daily of Liothyronine t3. Thank you

[helvella Administrator]

It is wrong to dose levothyroxine by weight.

I have said this many, many times and have written a blog to try to explain why.

For one example, two people who are otherwise identical. Both take levothyroxine only.

The differences between them could mean one absorbs 80% of the levothyroxine when the other absorbs only 60%. Surely that makes it clear that the second would need a higher dose - even if their bodies needed to absorb exactly the same dose?

Two people, exactly the same weight, one hugely fat, the other all muscle and dedicated to weightlifting. Pretty much fat itself needs no thyroid hormone. (Technically, the fat cells need some but not the actual fat.) The idea that they need the same dose is clearly wrong.

helvella's calculation document and spreadsheet can be can be found by following this link:

helvella - Estimation of Levothyroxine Dosing in Adults

A discussion about the use of formulas to estimate levothyroxine dosing. Includes link to a downloadable spreadsheet which calculates several of these.

helvella.blogspot.com/p/hel...

[RedApple Administrator]

5219, As already mentioned by  helvella your weight is not the way to determine the dose of levothyroxine that will keep you free from symptoms of hypothyroidism. You will get better help and support from members if you tell us the details of your most recent thyroid test results.

Ideally, this would be TSH, FT4 and FT3. If your GP won't test all of these on the NHS, then consider doing your own private test.

[5219 in reply to RedApple]

thank you. I did wonder so this why l asked on here. I have just had a blood test but from Gp and I’m sure it will only be TSH so I will have a private test done. It really annoys me that Gp’s don’t do a full test but I suppose it’s all about the cost. When I get the test done I will post on here and get your feedback. Thanks again

[RedApple Administrator in reply to 5219]

This is currently the best value at home fingerprick test randoxhealth.com/en-GB/at-h...

[helvella Administrator in reply to 5219]

Annoyance at failure to test what we regard as important is one of the most common themes here!

And it is especially important when you are taking any form of combination therapy.

Probably a good idea to make sure your B12 and folate are good as well.

[5219 in reply to helvella]

Yes I hear it so often. Bearing in mind that the thyroid controls most of our bodies it’s not good is it?

Yes I will check that as well. Thank you

[5219 in reply to 5219]

Another question I would like to ask should I take Vitamin D3 that has K2 in it as well? I have read that this helps calcium go to your bones and not your tissues and arteries.

[arTistapple in reply to 5219]

I read somewhere (should have noted it properly) that the three tests cost less than £1.00 per test. If you get annual tests by your GP, this adds up to the princely saving sum per patient of less than £2.00 per annum. That’s how much your health means to the powers that be. The NHS probably wastes millions, on testing hypos for many other conditions they don’t have, which probably are down to under medicating hypothyroidism.

[Algic in reply to arTistapple]

Yes I was told that too. I need to compare my results to current figures T4 and TSH test. The gp thinks I'm on too much -125mg of thyroxine. But my TSH is virtually no existent. I read the supporting research every single paper mentioned cost . I can't help thinking the cost to NHS of thyroxine went up so answer knock a few mg off here and there. But I'm naturally suspicious from experience.

[helvella Administrator in reply to Algic]

The cost of levothyroxine is very low.

And there are many circumstances in which a lower dose costs more than a higher dose! Though that works both ways.

For example, 100 is less expensive than both 75 and 25. (As single tablets.)

[arTistapple in reply to Algic]

The flaw is really most likely to be the GPs reliance on TSH. There are researchers who completely understand the whys and wherefores that this is wrong but this info does not seem to have reached endocrinologists and the GPs who take their lead from them. It seems this information may actually actively be being withheld and GPs who might be interested in helping patients are having their hands tied.

[Batty1]

It has not been my experience that doctors provide you thyroid medications based on your weight, we read about it and people keep saying this but for me this has never been something my Endo’s have done for me …. Its based on your labs and if your lucky to get endo who listens when you complain.

[helvella Administrator in reply to Batty1]

I think dose by weight had been very much ignored as an approach in the UK until the NICE NG145 thyroid guidelines were published in November 2019. Their use of 1.6 micrograms per kilogram has seen a flood of mentions/references.

And, in addition to what I said in my first comment, there is another reason not to just accept it.

If you are hypothyroid and get given a weight-based dose, it is very likely that you will end up over-dosed, at least temporarily. Even if the calculated dose is what you end up needing, it seems unlikely to me that you should jump straight onto 1.6 micrograms per kilogram.

Jumping from below optimum thyroid hormones levels to over maximum seems to immediately impose a huge stress on the body. It has to go from one abnormal state to another different abnormal state - instantly.

Doesn't it make so much more sense to go from one abnormal state to a less abnormal state - by offering, say, 75%/1.2 micrograms per kilogram? Enough to resolve much of the deficiency but with little risk of flipping over to being over-dosed. Get to a less abnormal state, then adjust.

From a personal experience point of view, I have very occasionally wondered if my levothyroxine dose was slightly too much. And absolutely hated it. Yet that would only have been by at most by 25 micrograms and probably less.