Thyroid UK

TSH 4.61 (0.4 - 4.0) under medicating!

After everyone's help and realising that I was being under medicated following a recent blood test, I have now been back to see the Doc. I thought you would like to know that he has upped my thyroxine by 25mg to 150mg and prescribed ferrous sulphate as my ferritin levels were a measly 16 ug/L (25-300). It was tough going and he wouldn't entertain the idea of any other supplements so I hope this is enough to raise my energy levels!

Folate was 5.5 (3-20)

B12 411ng/L (180-800)

Watch this space...

9 Replies

Bringing your ferritin levels up will be good as it needs to be above 70 for your thyroid medication to work effectively. Folate probably could do with supplementing before it goes even lower so maybe pick up some folic acid from your chemist or supermaket. B12 also should be higher, it's not horrendous but it should be higher than 500.

Just make sure you don't take the iron supplement anywhere near your thyroxine. Should be at least 4 hours between them.

Hopefully the combination of an increase of meds and the supplements will help you feel better soon.



I agree that decent iron and ferritin levels are highly desirable. But do you have any evidence that 70 is the magic number?


You got me intrigued enough to go hunting the web. :) For a while, all I could find was references to "experts say ferritin should be 70-90 for optimal conversion of T4 to T3". And 70 also seems to be the magic number in cases of hair loss caused by iron deficiency.

Anyway, eventually, I found this (references are at the bottom of the page):


A bit late to read right now - but thanks, will read.


Study referenced as 238 says:

Serum ferritin (SF) was measured using immunoradiometric assay. Iron deficiency was defined as SF of <15 μg/L.

Study referenced as 239 says something but the abstract is very thin and I could not find the full paper.

Study referenced as 240 says:

Criteria for case inclusion were: a) absence of any systemic diseases, except for iron deficiency without anemia (hemo-globin >12mg/dl, serum ferritin <12μg/l and transferrin saturation <16%)

That paper is fascinating and suggests that rT3 levels are higher in those with low iron.

Study referenced as 241 is, again, not available in full so cannot assess.

Study referenced as 242 is available and interesting, but in a quick look, I could not even find the word "ferritin".

Very interesting material. The response of the pituitary to TRH is blunted in low iron. Hypothermia in iron-deficiency might be mediated by lowered T3 availability, ...

Unfortunately, in my view, still nothing which really bags the "ferritin must be 70" statement!

I suggest that somewhere in the region of 70 might be reasonable. But the tests for ferritin vary in just the same was as thyroid hormone tests - from lab to lab. So the actual numeric value could also be expected to vary.

I suggest that other factors such as inflammation, even vitamin C deficiency, need to be considered when interpreting any ferritin result - not simply the number on its own.

And I also suggest that even if 70 were optimum, it should be clearly recognised that there is a scale - and that 60 is better than 50, which is better than 40, ... There is not a sudden 70 is good; 69 is bad.

Finally, ferritin is an iron storage protein. It takes time with improved iron for ferritin levels to rise. At some points it might be possible to have entirely adequate non-ferritin iron levels, with the ferritin levels lagging behind.

(I have always felt ignorant of how iron "works". If anyone reading the above feels I have made a big mistake, please let me know.)



Hi Rod,I've seen it mentioned in several places amongst them and the link posted by LilyMay. Why 70 I really have no clue.


That's good he has raised your dose. Next time, ask if he would add some T3 (he may fall of his chair) but we can give you a reference which may enable him to prescribe a little.

Just remember before your next blood test to take your meds afterwards and not before and have it as early as possible.

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Thank you, may I have the reference - just in case.


Email and ask for a copy of Dr Toft's article in Pulse Online.


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