Thyroid UK
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Blood test results

I was diagnosed with borderline underactive thyroid 2 years ago and have been taking 25mcg of thyroxine daily. My latest blood test results are:-

Serum free T4 level is 11 - range 7.8 - 21

Serum TSH level is 4.2 - range 0.35 - 4.7

Doctor says these are fine and to continue with the thyroxine.

My serum ferritin level in February 2014 was 11 and my doc gave me Sytron iron supplement 10ml x twice daily and my level is now 55 (range 15 - 300) and he wants me to try half the dose and then have a further blood test.

Serum vitamin B12 is 234 ( range 180 - 11300 - he says this is fine.

These levels seem low according to posts I have read on this site - can anyone help?

Thank you!

4 Replies

Minsterlady, You are very undermedicated with TSH 4.2. Medicated patients are generally more comfortable when TSH is just above or below 1.0. Scroll down to Treatment Options to read Dr. A. Toft's views on TSH and FT4 levels and 'euthyroid' status

Email for a copy of the article to show your GP. If he doesn't increase your thyroxine I would suggested seeing another GP at your practice for a 2nd opinion or change GP practice.

Ferritin is optimal at 70-90. 500mg-1,000mg vitamin C taken with each tablet aids absorption. Iron should be taken 4 hours away from Levothyroxine. Don't take iron for 24hrs prior to your blood test.

Your B12 is low but not deficient according to NHS standards. Most of us supplement methylcobalamin sublingual lozenges, sprays or patches when B12 is <500 and aim to be high in range. You need to stop supplementing B12 4/5 months before retesting.


Thanks for your advice Clutter, very much appreciated. I am sure I do need extra levothyroxine as I feel cold even when the room temperature tells me that I should be warm enough, I have restless legs, cramp at night and my muscles ache. I used to be able to walk really quickly but notice I am slowing down a lot these days - goodness, I am getting to be a grumpy old woman, LOL.

I started taking magnesium to help with the cramps etc and I shall get some vitamin B12 and see if I feel any different.

thanks again.


Minsterlady, has your vitamin D been tested? Low vitD can cause muscle and bone pain.


I have about 40 items on the printout from my last blood test results but vit D is not on the list. I forgot to mention that my main concern is the lack of energy I have as I get so tired. I thought that the iron supplement would cure that but from what I can gather from past posts the culprit looks likely to be my thyroid and from what you told me an increase of the levothyroxine should sort that out - I certainly hope so!


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