Thyroid UK
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Full results this time with ranges - what does this mean?

Hi sorry to keep asking...I have a print of my results now. I've been having symptoms for a while that could suggest thyroid issues but equally could be something else. GP suggested taking small dose of thyroxine; now seeing an endro (will see with these results at end of month now). I'm trying to work out if it could be a T3 conversion issue or secondary thyroid.

FT3 3.4 pmol/L 4-6.8

FT4 13.6 pmol/L 12-22

TSH 5.1 miu/l 0.3 -4.2

Thyroid Peroxidase ABS 12 iu/mL 0-34

TPO <35 iu/mL

Also last blood pre this show low Vit D and raised IGF and Prolactin

Any thoughts/advice on the results above very gratefully received

10 Replies


TSH is over range which means you have primary hypothyroidism. T4 is low in range but T3 is below range so Levothyroxine replacement will be helpful in raising both. T3 is the active thyroid hormone so having T3 below range will make you feel very unwell.

Thyroid peroxidase antibodies (TPO) are under range which rules out autoimmune thyroiditis (Hashimoto's) causing hypothyroidism.

For maximum absorption Levothyroxine should be taken with water 1 hour before, or 2 hours after, food and drink, 2 hours away from other medication and supplements, and 4 hours away from calcium, iron, vitamin D supplements, magnesium and oestrogen.

It takes 7-10 days for Levothyroxine to be absorbed before it starts working and it will take up to six weeks to feel the full impact of the dose. Symptoms may lag behind good biochemistry by several months.

You should have a follow up thyroid test 6-8 weeks after starting Levothyroxine. Arrange an early morning and fasting (water only) blood draw when TSH is highest, and take Levothyroxine after your blood draw.

How low was your vitD and how much are you supplementing?

1 like

Thanks so much for help. Vit D was 13 I've been on 1000 ug of D3 a day.

I just can't explain to people how poorly I've felt.



When my vitD was <10 I was prescribed loading doses of D3 40,000iu daily x 14 days followed by 2,000iu daily x 8 weeks which raised vitD to 107.

Ask your GP to read the NICE CKS and prescribe the doses recommended or buy your own D3 on Amazon. If you use Amazon please use the affiliate link

Make sure you take vitD 4 hours away from Levothyroxine.


Thank you - my friend had Vit d as low as my reading and was given some mega dose.

Thank you for the links - I will use these, Liz


Lizj - can you check the range for FT3. That range is very narrow. We usually see 3.1-6.8 when 6.8 is the top of range.


Hi SeasideSusie

I just check the pathology report and it is what it said


Gosh, that is such a narrow range!


Is that bad?


Oh, not necessarily, it's just unusual. It doesn't make any different really. If it had been 3.1-6.8 you would have been very low in range. As it is 4-6.8 then you are under range. So whichever way, your FT3 is poor.

Clutter has said it all really, the only thing I can add is that you really need to take Levo for a while, you will probably end up with increases in dose, then see how your levels are and then you will be able to see how well (or not) you convert.


Thank you so much. This forum is amazing and it's so helpful having people with experience and knowledge sharing - I really appreciate it. Liz


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