LEVO CALCULATOR

[Jelley93]

omnicalculator.com/health/l...

Found this if its useful to anyone. I inputted my data and it shows I need 124.1mcg I am on 125 so looks accurate.

[tattybogle]

mmm.... using 'formula' to set initial doses is problematic .. helvella has done some work on this and posted recently on the subject.

One issue is there are several different formula that could be used , often giving different results . The other is that the cut off's for different groups can mean the recommended dose changes massively from being just 1 day older.

For example i'm 54 and just put my details into this calculator and it came out with a starting dos of 25-50mcg..... i'd be pretty unwell on that .. i currently take 112.5mcg

[tattybogle in reply to tattybogle]

just played around with it for an extreme example ... if you were only 51 (with no heart condition) and you told it you weigh 300 Kg .... even if you put your T4 is 'low' .... it still tells the Doctor to start at 25-50mcg and the target TSH result is 'Mid lab range'So you'd get stuck on 25or 50 and left there even if your TSH was over 2

I imagine a 51 yr old (of any weight, let alone 300Kg lol ) would need rather more than 50mcg Levo to have any useful effect.

My TSH didn't drop below 2.5 until i was on over 150mcg

[SlowDragon Administrator]

For anyone over 50 years old it gives no guidelines on ultimate dose other than to start on 25-50mcg

There’s absolutely no mention of what full replacement dose is likely to be for anyone over 50

Increase the dose by 25 mcg every 3 - 4 weeks until the full replacement dose is reached.

Particularly worrying is this statement

The TSH (thyroid-stimulating hormone) goal is mid-normal range.

[Goldengirl01 in reply to SlowDragon]

I’m meant to be on 66.2mcg according to my weight and height. I’m on 100mcg at the moment

[helvella Administrator]

I believe it is unethical to publish such a calculator without also making the formula available for inspection. My spreadsheet makes clear what it is doing - or is at least intended to!

helvella - Estimation of Levothyroxine Requirement in Adults

A spreadsheet with active formulas which work out possible levothyroxine requirements including NICE NG154 guidelines.

dropbox.com/s/aciho6m7x6f1e...

They mention the Devine formula - which is just one of the calculators of ideal body weight from sex and height. But I couldn't find the formula they use for levothyroxine.

It is also, of course, implicit in any levothyroxine calculator that the only treatment considered is levothyroxine monotherapy.

Funny how NICE use age 65 as their cut-off but this site decides to use 50. 15 years is a big difference.

[helvella Administrator in reply to helvella]

Omni have replied to an email I sent:

Hello,

Thanks for reaching out! For the dosing, we use data available in the summary of product characteristics or product description, e.g., reference.medscape.com/drug... -> 1.7mcg/kg for hypothyroidism, 1.0mcg/kg for the subclinical hypothyroidism. We count the dose for the ideal body weight, and to find that, we use Devine formulas:

• 50.0 kg + 2.3 kg per every inch over 5 feet for men

• 45.5 kg + 2.3 kg per every inch over 5 feet for women

Best regards,

Bogna Szyk

Omni Calculator

omnicalculator.com

Note that this does NOT include their age 55 cut-off! Nor does it say how to handle anyone shorter than 5 feet tall.

[ElephantShrew]

I like the idea of this but i'm not sure about the approach.. I just tried it out with my details and it says my dose is 96.7 mcg. I'm currently on 100 mcg and still feeling tired and under medicated. I think the issue is this:>Input the height of your patient. You may be surprised by this, but our calculator works either on actual weight, or on ideal body weight in case of people above their ideal weight. It uses the Devine formula, which varies depending on sex.

So i'm assuming that - because i'm overweight, which i'm struggling to lose because i'm hypothyroid - it's ignoring my actual weight and calculating by my ideal weight. Not sure this is a valid approach although obvs is complex.

So yes i am surprised :). I wonder why they've taken this approach and what it's based on?

[helvella Administrator in reply to ElephantShrew]

Did you try the multiple formulas in my spreadsheet? (Linked earlier in thread.)

[ElephantShrew in reply to helvella]

hiya! i've only tried with the generic 1.6mcg*body weight in kg from the NICE guidelines, but your spreadsheet has much more going on! i hadn't realised there were so many approaches (also i appreciate the styling, that's really nice)

So NICE puts me at 125 mcg, Wisconsin at 130, Hull at 158 . I'm only hypothyroid, no thyroidectomy or lobectomy so i'm not sure if i qualify for the other formulae?

I'm only 6 months post-diagnosis, still working towards a dosage which feels right, next tests next week, so these are all good data for next GP consult! Do you mind if i ask where the Hull formula comes from and if they say why they chose these numbers etc?

Also: thankyou! 😊

[helvella Administrator in reply to ElephantShrew]

I think you might now realise why I am deeply sceptical of using formulas - other than a best-guess in some circumstances and a "sanity check" on existing doses.

[ElephantShrew in reply to helvella]

Yes! The 'best-guess' side is helpful for where i am in the process: in March I was feeling really sad - emotional adjustment to finding out I have a chronic condition and still feeling exhausted and no concentration 4 months in - and being able to check the guideline numbers really helped, like it's ok if i don't feel better yet because there is room for more adjustment and hopefully it will get there? (hopefully)

[ElephantShrew in reply to helvella]

... and i just found the ref links at the bottom - sorry! hadn't scrolled down enough😊

[BB001]

Personally I think the advive to start at 25-50mcg is OK. This gives one's body the chance to adapt. What I disagree with is the phrase 'The TSH (thyroid-stimulating hormone) goal is mid-normal range' as there is research that says once on thyroid meds TSH should be 0.5-1 (sorry I can't remember the source). Other research e.g. by Dr Toft says TSH shouldn't be used for monitoring thyroid euthyroidism (I.e. normal thyroid). This calculator propagates the myth that TSH should be used for monitoring..

[Meanbeannyc]

According to that calculator it says I should be on 53mcg of levo…

I have no thyroid and would probably end up dead on 53mcg of levo. lol

I am currently and unfortunately on 112 lol