Thyroid function tests: I am still sifting... - Thyroid UK

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Thyroid function tests

kim1965 profile image

I am still sifting through my blood test results and would like to understand if it is normal practice that if your Free T4 results come back within normal ranges that they do not test TSH and freeT3 ?

My head is in a right spin over this , and whilst i know I cannot change whats past I want to go into the future more well informed.


10 Replies

Kim It is usually TSH only that is tested. If you are lucky they will also test ft4. If TSH is in range they will not test ft3 - GP surgeries tend to steer clear of ft3.

kim1965 profile image
kim1965 in reply to Lalatoot

Thank you ..I really need to learn more about this condition but struggle to retain informatiom.This forum is proving to be very helpful 🙂

SlowDragon profile image

Essential to test vitamin D, folate, B12 and ferritin at least once a year too

GP rarely tests

kim1965 profile image
kim1965 in reply to SlowDragon

Thankfully these things are checked i had very low ferritin(4) when first diagnosed .Thank you

SlowDragon profile image
SlowDragonAdministrator in reply to kim1965

So what are your most recent vitamin results

Optimal vitamin levels are

Vitamin D at least around 80nmol and around 100nmol may be better

Serum B12 at least over 500

Folate and ferritin at least half way through range

Ferritin- that’s usually at least around 70

kim1965 profile image
kim1965 in reply to SlowDragon

Vit D was low 25 but have been prescribed a two tablets once a week course to be taken over 6 weeks.

B12 was 857 (range 200-900)

Ferritin 120 (range 30-250)

Folate 3.3 (range 2-17)

The brand of Levo I am on is North star

I get my prescription every 2 months , the time before last was a different brand because of a recall on Northstar.

SlowDragon profile image
SlowDragonAdministrator in reply to kim1965

B12 is good, do you supplement?

Folate is low supplementing a good quality daily vitamin B complex, one with folate in (not folic acid) may be beneficial.

This can help keep all B vitamins in balance

Difference between folate and folic acid

B vitamins best taken after breakfast

Thorne Basic B or Jarrow B Right are recommended options that contains folate, but both are large capsules. (You can tip powder out if can’t swallow capsule)

IMPORTANT......If you are taking vitamin B complex, or any supplements containing biotin, remember to stop these 7 days before ALL BLOOD TESTS , as biotin can falsely affect test results

SlowDragon profile image
SlowDragonAdministrator in reply to kim1965

So you are on 75mcg levothyroxine now

And getting 50mcg and 25mcg tablets, is that correct

Northstar 50mcg and 100mcg are Accord brand of levothyroxine

But Northstar 25mcg is Teva

Accord don’t make 25mcg tablets

Teva brand upsets many people, so if you find Northstar 25mcg doesn’t agree with you….request higher number of 50mcg tablets per month and cut in half to get 25mcg

List of different brands available in U.K.

Posts that mention Teva

Teva poll

Once you find a brand that suits you, best to make sure to only get that one at each prescription.

Watch out for brand change when dose is increased or at repeat prescription.

New guidelines for GP if you find it difficult/impossible to change brands

If a patient reports persistent symptoms when switching between different levothyroxine tablet formulations, consider consistently prescribing a specific product known to be well tolerated by the patient. If symptoms or poor control of thyroid function persist (despite adhering to a specific product), consider prescribing levothyroxine in an oral solution formulation.

Physicians should: 1) alert patients that preparations may be switched at the pharmacy; 2) encourage patients to ask to remain on the same preparation at every pharmacy refill; and 3) make sure patients understand the need to have their TSH retested and the potential for dosing readjusted every time their LT4 preparation is switched (18).

Levothyroxine is an extremely fussy hormone and should always be taken on an empty stomach and then nothing apart from water for at least an hour after

Many people take Levothyroxine soon after waking, but it may be more convenient and perhaps more effective taken at bedtime

No other medication or supplements at same as Levothyroxine, leave at least 2 hour gap.

Some like iron, calcium, magnesium, HRT, omeprazole or vitamin D should be four hours away

(Time gap doesn't apply to Vitamin D mouth spray)

If you normally take levothyroxine at bedtime/in night ...adjust timings as follows prior to blood test

If testing Monday morning, delay Saturday evening dose levothyroxine until Sunday morning. Delay Sunday evening dose levothyroxine until after blood test on Monday morning. Take Monday evening dose levothyroxine as per normal

REMEMBER.....very important....stop taking any supplements that contain biotin a week before ALL BLOOD TESTS as biotin can falsely affect test results - eg vitamin B complex

SlowDragon profile image
SlowDragonAdministrator in reply to kim1965

How low was vitamin D ? Retest vitamin D when finish prescription from GP

You will likely need to self supplement to maintain

NHS Guidelines on dose vitamin D required

GP will often only prescribe to bring vitamin D levels to 50nmol. Some CCG areas will prescribe to bring levels to 75nmol or even 80nmol

GP should advise on self supplementing if over 50nmol, but under 75nmol (but they rarely do)

But with Hashimoto’s, improving to around 80nmol or 100nmol by self supplementing may be better

Once you Improve level, very likely you will need on going maintenance dose to keep it there.

Test twice yearly via NHS private testing service when supplementing

Vitamin D mouth spray by Better You is very effective as it avoids poor gut function.

There’s a version made that also contains vitamin K2 Mk7. One spray = 1000iu

It’s trial and error what dose we need, with hashimoto’s we frequently need higher dose than average

Vitamin D and thyroid disease

Vitamin D may prevent Autoimmune disease

Web links about taking important cofactors - magnesium and Vit K2-MK7

Magnesium best taken in the afternoon or evening, but must be four hours away from levothyroxine

Vitamin K2 mk7

Hi Kim. If you are already taking levo the GP usually checks the TSH and the FT4. when checking your thyroid results in case you need a dose adjustment. That's my understanding.

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