Many thanks for all your help, advice and suggestions last week. I'm a bit confused as my pinprick tests have returned...
nhs test (late afternoon)
FT4 11 and tsh 3.7
Pinprick test (fortnight later, 7.15am)
FT16 and tsh 3.4
Antibodies all fine along with T3.
Is it usual for such a difference in FT4 please or do you think I need to try another pinprick or nhs to check please? The only difference was B12 was 3 days overdue for the nhs test and obviously 2wks into the month for the pinprick? Could the lack of it cause thyroid to do this do you think?
Thanks for your time!
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Jo5454
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Was there any difference in the time between your last dose of T4 and the time of testing? This can have a discernible effect on measured FT4. But also on therapy your FT4 can vary, though, as expected, your TSH doesn't respond quickly (same result). There's also perhaps a 1 pmol/L variation in a test's reliability which could add to the difference in the two tests. In your case the TSH is saying that you are underdosed if on T4 therapy. TSH down to 1 or less should be the aim. No matter if your FT4 goes above range - it's the FT3 (which isn't measured) which tells the whole story as to your correct dosing.
Thank you diogenes, I'm not taking anything for thyroid, I've Been trialing iodine, selenium, magnesium, alongside other vitamins I take (plus monthly b12) to correct an iodine deficiency for 6 months. Many people helped me last week on here with the iodine...but I'm confused as to the FT4 result.
The f3 is 5.25 (3.1-6.8)
I've added the the ranges of both results further down...thanks for your help.
If you are not hypothyroid actually, your TSH is not optimal and it looks as if your thyroid is struggling. If so, your FT4 will vary from time to time as to how the struggle is going. Iodine is not helping the situation in that taking it in too large a quantity can partially suppress thyroid activity and alter results., So it may be the time between taking iodine and testing that changes the FT4.
thats interesting thanks. I take the iodine at lunchtime, so yes that could explain. Also if the t4 struggles then maybe the thyroid is struggling more when b12 is due too. Thanks for your answer.
OK, so the TSH is comparable, ranges don't vary that much with TSH.
The FT4 result is not comparable because the ranges are so different so we have to work out the percentage through range to compare.
Ft4 11 (8-21) = 23.08% through range
Ft4 16.4 (12-22) = 44% through range
[If you want to do this yourself, here is a link to the calculator: chorobytarczycy.eu/kalkulator - use the "hormony tarzycy" tab for thyroid, the other tab for any other test]
Antibodies aren't raised so for this test they don't suggest autoimmune thyroid disease (Hashimoto's) but one negative test doesn't rule it out as antibodies can fluctuate.
As Diogenes has mentioned, your TSH level suggests your thyroid is struggling.
Thank you Seaside Susie, I've obviously been totally misunderstanding ranges.
I presumed if something was measured in for instance pmol/L , like the 16 and 11, then that measurement is equivalent, one I higher, one lower and that different establishments just use different ranges to determine deficient?
Thanks for that calculator, will make a note of that👍
Ranges are apparently based on a healthy, local population, which is why ranges vary from lab to lab. For instances, where I live the range fot FT4 is 7-17, others we see here are 9-19, 11-23, 12-22, etc. So to compare our results, if ranges are different, we just need to work out the percentage through the range.
And no, I've always been told I don't need iron tests, even tho my ferritin has been down to 12 before.
Again, I did a pinprick for that a while ago, even though ferritin was in the 40s the two parts of the test were indicating I needed to take iron, without having notes here, think it was Tibc and transferrin?
Think i'llndo that again too, I've started upping iron, but guess that won't matter...thank you.
Eating liver or liver pate once a week, plus other iron rich foods like black pudding, prawns, spinach, pumpkin seeds and dark chocolate, plus daily vitamin C can help improve iron absorption
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Can I have thyroxine now? 
im new and need help reading my tests please not on any medicaten yet im being mest about but have just about all the thyroid symptons xx
Quick NHS Blood Test Query
Checkup of multinodular goitre at ENT
What might cause a spike in FT3?
