Am I right that the average recommended dose of Levothyroxine is 1.6mcg per kg patient weight? It seems to me that many people on here are on very low doses. Does that mean that quite a few patients are being undertreated?
I'm 68.5kg so my dose should be around 110mcg daily. I might need slightly higher or lower. Obviously, blood tests are used to monitor TH levels but how do we know where our FT4 baseline is?
Are doctors assuming people are optimally dosed when their FT4 is anywhere within the population range? You could be right at the bottom of the FT4 range when really your natural baseline should be nearer the top to be euthyroid, for example.
I keep seeing people on 50mcg or even 25mcg. Are you undertreated or do you weigh very little?!
Not sure if I'm thinking along the right lines or have mistaken the dosing recommendations.
Written by
Agitator23
To view profiles and participate in discussions please or .
You are right many people are under replaced as GP's just look at TSH and like you say an in range TSH and possibly fT4 is good enough if they test for it
They aren't allowed in many places to test fT3 and GP's mostly wouldn't have a clue what they mean anyway
While I accept it can be used to give an idea of where the dose might end up, using it for an individual is, I think, often as likely to push towards the wrong dose as the right dose when you get anywhere near a full replacement dose.
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's calculation document and spreadsheet can be can be found by following this link:
The blogspot you've written is really detailed and very clear! I'm much more informed on the pitfalls of dosage. I'm on 100mcg going up to 112.5 as soon as new prescription is available. Alternating 100/125. Endocrinologist wants me to get to around FT4 19 or 20 pmol/l. TSH is being ignored in my case (central hypothyroidism).
These things are not easy to explain. And I have to simply guess whether people who read the blog find it ridiculously complicated, or so obvious it's not worth saying.
Feedback is welcome! Even if it points out what is wrong.
Yes…..we see many patients with clear hypothyroid symptoms, left on only 25mcg, or 50mcg or 75mcg levothyroxine daily for years or even decades
GP only testing TSH and refusing to increase dose if TSH is “within range “
Patients are being very badly let down, putting their trust in GP and becoming very unwell as a result of being left on totally inadequate dose of levothyroxine
Often with severe vitamin deficiencies as direct result
It’s totally inappropriate to only test TSH
patients should also be advised to get thyroid blood tests early morning and last dose levothyroxine 24 hours before test
Vitamin testing at least annually
If symptoms remain despite Ft4 in top third of range and vitamin levels, then patients should
A) be able to get TSH, Ft4 and Ft3 tested
If Ft4 is high and Ft3 low then
B) referral on NHS to a thyroid specialist endocrinologist to determine if prescription of T3 alongside levothyroxine would be appropriate
I have seen the 1.6 per kilo but in my case it was wrong. I have also found various sites stating that it depends on the BMI of the person, very confusing. Some state that a person with no thyroid should take a larger dose perhaps 2. or even 2.2 per kilo,
When i was in my 30's and 40's i needed 150mcg .... ( i was subclinical when diagnosed TSH 6.8, TT4 in range , TPOab >3000 , so it's safe to assume i had some functioning thyroid left)
when i was 50 i became overmedicated and needed to reduce dose to 125mcg ... then a few yrs later to 112mcg. (lower dose probably explained by menopause a couple of yrs earlier~ estrogen level has an effect on thyroid hormone binding )
my weight has never changed significantly during all this time, a few lb's either way .... ( i'm one of those who only put on a few lb's before diagnosis/ treatment , and have never had an issue with weight gain despite being hypo for 28 yrs )
if you went by 1.6mcg / kg , my dose 'should' have been around 96-99 mcg / day for all of this time. but in practice 125mcg was not enough for much of it ..... i recently tried 100mcg for a while ...which felt passable....... then tried 87.5mcg for a few months and that was definitely not enough.
so now that i am nearly 60 , "1.6mcg /kg " does seem 'about right' , but when i was younger / fitter / more active /had a lot more muscle , it would have left me significantly undermedicted
from what i've read , 1.6mcg / Kg was only ever intended as a 'ball park' guess, to give doctors a very rough idea of the dose likely to be needed when they have removed someone's thyroid, nothing more .
In practice some need more than that, some less .. sometimes significantly.
The 1.6mcg per kg weight is in the NICE guidelines so useful at least to cite when discussing with your GP when all they ever look at is TSH, in my case suppressed!
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.
NDT and results
Help - Levothyroxine dosage dilemma 
Dosage advice on levo only??
And now this; High TSH AND High FT4
Levothyroxine optimised?
