Is it worth getting T4 and T3 tested privately? - Thyroid UK

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Is it worth getting T4 and T3 tested privately?


Hi all,

I have hypothyroidism and had a TSH test on Monday which revealed TSH of 3.1 (ref range = 0.4-4.9).

I'm on 50mcg levothyroxine and have a GP appt coming out where I'm going to argue for a higher dose (perhaps 75mcg?) as I still have lots of hypo symptoms.

I'm struggling to get my GP to request T4 and T3 tests. Would it be worth getting these done privately? Can anyone recommend a good company?

I did however manage to convince them to test vitamin D, iron, folate and B12. I'll get the results of these tests on Monday.


5 Replies


It's very likely policy in your area that FT4 and FT3 aren't tested when TSH is within range. Some areas test TSH only, some test TSH and FT4 as standard.

But the fact that your TSH is 3.1 (0.4-4.9) should be enough for your GP to raise your dose. If not refer to Dr Toft's article in Pulsle magazine

"The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range - 0.2-0.5mU/l.

In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l. Most patients will feel well in that circumstance.

But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l.

This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l)."

Dr Toft is past president of the British Thyroid Association and leading endocinologist.

You can obtain a copy of the article by emailing Dionne at

print it and highlight question 6 to show your doctor.

Also he can see from this table here (scroll down to Thyroxine Replacement Therapy in Primary Hypothyroidism) where you'll find a box which states:

Replacement Therapy:


0.2 - 2.0 miu/L Sufficient Replacement

> 2.0 miu/L Likely under Replacement

If you want to do your own tests, do one that tests TSH, FT4 and FT3 all at the same time, not just FT4 and FT3.

Medichecks Thyroid Monitoring use code MED99 before the end of this month for 20% discount, but first check tomorrow (Thursday) to see if it's on offer (you can't use the code with offer prices).

Blue Horizon Thyroid Plus Three 15% off with code sept15 popped up whilst I was just looking.

Both can be done by fingerprick or venous bood draw at extra cost.

Mogget in reply to SeasideSusie

Thanks very much for your helpful response - much appreciated! I've obtained a copy of the article and will take it to my GP. Fingers crossed.


Suggest you ask GP to agree to 25mcg dose increase and retest in 6-8 weeks

Little point paying for private test at moment, unless GP refuses to increase dose

Many people find Levothyroxine brands are not interchangeable.

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.

Many patients do NOT get on well with Teva brand of Levothyroxine. Though it is the only one for lactose intolerant patients

Mogget in reply to SlowDragon

Thanks very much for the advice. Yes, I'll see how I get on with the dose increase - I guess no point in testing t3 and t4 if the increase makes me feel better. I didn't know that about the brands - thanks for the tip.

SlowDragonAdministrator in reply to Mogget

Quite possibly will need further 25mcg increase(s) over coming months/years

We have to increase slowly. Retesting 6-8 weeks after each dose increase

All thyroid tests should ideally be done as early as possible in morning and fasting. When on Levothyroxine, take last dose 24 hours prior to test, and take next dose straight after test. This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, GP will be unaware)

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