300 mcg of Levothyroxine?

[Chelle1310]

G.P. wants me to increase my dose from 225mcg straight up to 300mcg, surely this is way too much all at once?

[SeasideSusie Remembering]

Dondo1310

Yes, it a ridiculous amount to increase by. All dose changes should be 25mcg.

300mcg would be a large dose. Have you had full thyroid tests:

TSH

FT4

FT3

Thyroid antibodies

If you post your test results with their reference ranges, we can try and see why your GP wants to make such a dramatic increase.

[Caesard in reply to SeasideSusie]

Depends on where you start from. Tests should shed some light. Otherwise true, a large increase on a already large dose.

[jimh111]

There's no problem going straight to 300 mcg assuming your fT4 is not high or you still have signs and symptoms of hypothyroidism. It'sbetter than dithering and leaving you hypo. Of course if it turns out to be too much it will need to be reduced.

[shaws Administrator]

Do you have print-out of your most recent blood test results with the ranges that you can post?

300mcg at one time didn't seem a high dose as some people do require a higher dose than normal.

However, I wonder if you have Thyroid Hormone Resistance and if you do, only T3 alone will relieve your symptoms. If you are in the UK, I doubt it will be prescribed - even if you could have a 'trial of T3' it might improve your condition.

One of our Advisers (deceased) was an expert on Thyroid Hormone Resistance.

web.archive.org/web/2010103...

[Angel_of_the_North]

It's too much for most people in one go. But I'd accept the increase and just start with 250mcg for a month, then 275 for a month then 300 (that way you'll have some spare tablets as well in case of a late prescription).

[helvella Administrator Thyroid UK in reply to Angel_of_the_North]

That seems a sensible approach. I'd not want to increase dose by a third in one go!

(In the best of all possible worlds, re-testing each month!)

[Beata_s in reply to helvella]

New to all this - why isn’t it good to increase or decrease rapidly please ?

[helvella Administrator Thyroid UK in reply to Beata_s]

As I see it, the ONLY time that rapid increase is justified is in an extreme situation. For example, someone in or approaching myxoedema coma might need a large dose initially. Similarly, someone on a dose which is obviously much too high for them might need to cut back rapidly.

In general, it is NEVER good to increase or decrease rapidly.

(Initial dosing is another special case because we see that very low doses such as 25 can end up reducing effective availability of thyroid hormone in some people. Hence starter doses of, arguably, 50 to 100 in most people.)

In naval gunnery, they fire a shell at the target. Most likely it will either fall short, or go beyond that target. So they make a sensible but significant adjustment and fire another shell. If they now have one short and one long, they can work out with high precision how to adjust the gun to hit the target with the third shell.

In thyroid, you can't do this. Changing someone from being under-dosed to being over-dosed causes so many issues. And we really do not have a scale which can identify how much levothyroxine will raise FT4 by, say, 2 and drop TSH by 1.2 (or whatever is required). We can see "more is needed" but only guesswork as to exactly what increase (or decrease) is needed.

Many people here have experienced being over-dosed on levothyroxine. Most of those who have described it say it is a horrible experience. Why, then, be so heavy-handed with dose adjustments?

[Beata_s in reply to helvella]

Thank you for explaining makes sense 😊

[jimh111 in reply to Beata_s]

It's a question of making a good judgement based on symptoms and blood test resutls. It's becoming more common to start patients off on 100 mcg rather than 25 or 50 mcg as it avoids prolonging recovery. In this case I'm assuming the doctor has the results and it makes sense to go from 225 to 300, perhaps the patient has still some way to go. By looking at the fT4 on 225 you can get a rough idea of how much would be required to bring fT4 up to better levels.

In the case of levothyroxine even drastic dose changes take about a month to approach full effect. This is not true of T3 medications where one should be more careful.

[LAHs]

And here is another approach. You may be feeling unwell because you do not have much Free T3. This would mean that you are a bad converter. You might want to get Free T4 and Free T3 measured then, after making sure you have the correct units, work out your FT4/FT3 ratio, it should be around 4 if it is less than, then "~OK", if it is greater than then you have a conversion problem and no matter how much T4 you throw at it you will probably not make enough T3 to make you feel well.

Watch out for the units though. My lab gives FT4 in ng/dL and FT3 in pg/nL so the ratio is FT4/FT3*10 - so long as those are the units your's are measured in. If not, there are many unit conversion calculators on the internet. The trick is to get the units the same for this one, (unlike TT3/TT4 which is different and whose answer is about 17 - 20)

You may also want to get your rT3 measured while you are at it, just to make sure your conversion is not bypassing the FT3 and going straight to rT3 - but we'll deal with that one later after we have determined the FT4/FT3.