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Thyroid UK
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Baffling blood test results

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Can anyone advise? Told to stop levo beginning of december 2018.so no meds at all for thyroid, not even thyroid support for blood test. Had blood test yest. Shows t3 is high. How can this be? Under immense stress at work at the moment but unsure how t3 can be so high?





(0.3 - 5.0)

Free T4



(7.9 - 16.0)

Free T3



(3.8 - 6.0)



Serum Ferritin



(15 - 300)

Ferritin >15 and <100ng/mL. With low Hb and MCV,

a normal ferritin in the presence of inflammatory

changes does not exclude iron deficiency.

10 Replies

What do you mean by "not even thyroid support for blood test"? Have you been taking a particular supplement, that you stopped just before the test, and if so, what are its ingredients?


Hi maisiegray. When i stopped levo i was taking nutrithyroid. Endo said to stop that so no meds or support for over 7 weeks when blood test taken


It is unusual to see a high T3 in the absence of medication (except with Hyperthyroidism). If you have autoimmune thyroid disease (graves or hashimotos), it is possible to get transient spikes in thyroid hormone levels as your thyroid gland deteriorates.

Thus, have you ever had your TPO and TG antibodies checked? If one or both are high, this could explain the increased fT3 value. If this is the case, then a low dose of thyroxine (e.g. 50mcg) could be initiated to prevent subclinical/pre-hypothyroidism from producing symptoms. This would increase your fT4 and lower TSH to a more normal level.

TSH is slightly elevated, and T4 is slightly on the low side; but the range is unusually low (I usually see around 12 - 22 pmol/L), so it may be that your fT4 is normal, since your result is a little more than half way up the range given.

Ferritin is pretty ideal, most studies suggest the healthiest range is 80 - 100, with little benefit and greater incidence of illness seen above 100. However a full blood count including haemoglobin count (assuming this is what hb refers to) and MCV (average volume of red blood cells) is required to fully rule out an iron deficiency when it is suspected; which is what the note is pointing out.


You need both TPO and TG thyroid antibodies tested plus vitamin D, folate and B12 too

Ask endocrinologist to test, or order privately

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also extremely important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially if Thyroid antibodies are raised

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and fasting. Do not take Levothyroxine dose in the 24 hours prior to test, delay and take immediately after blood draw. This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

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I had folate, vit d, b12, tpo and tg tested at beginning of december. All absolutely fine. Endos next step was to put me on ndt but cant see him doing this if t3 already high


How do you feel now? With your good free T3 you should not have hypothyroid symptoms. If you do it could be due to thyroid hormone resistance. This is genetic so if family members have thyroid or autoimmune disease that would support this possibility.


Hi hugh

I feel absolutely awful.absolutely exhausted, no weight loss. Cognitive impairment.no family history at all re thyroid


I am guessing that you were diagnosed based on TSH and T4. This may work for most people but it looks like, based on your Free T3, that your diagnosis was wrong.

I think you previously took NDT - did you feel better on it? If so it appears that you need very high Free T3, a pointer to thyroid hormone resistance.


Hi hugh. Yes i did try ndt and felt really well for 2.5 years. But then felt really ill and blood test showed t3 over range. Tried levo.felt well for first 3 weeks on very low dose 50mg but started to feel ill. T3 was 5.5 ( same reference range as above). But now on no meds at all since mid december and t3 over range. Have endo appt on friday. I dont know what they can do to treat me. They were going to try ndt again but cant see how they will now as t3 too high. If it is thyroid resistance how would they treat it?


I know an endo who freely admits that doctors are obsessed with blood test results. As you previously felt really well for 2.5 years on NDT it confirms that you need to take thyroid hormones. How you feel is much more important than the blood test results.

After the 2.5 years when you felt really ill it is likely that you needed to increase the NDT - I assume you had hypo symptoms at that time.


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