Thyroid UK
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Confused... Blood test readings

I was diagnosed with an underactive thyroid 2 years ago and I am on 75mcg Levothyroxine. I have finally asked for a copy of my results but am having trouble deciphering the result. I was given a printout just showing figures dating back to 2013. These are the most recent readings:

Serum free T4 (pmol/L) 18 Serum TSH (miu/L) 2.41.

Just really wanted to find out if these are within the normal range.

Any help would be very grateful.

6 Replies

I'm afraid you'll have to go back and ask them for the range for the FT4, as they vary from lab to lab. But your TSH looks as if your thyroid is struggling. Has it always been that high?


Hi Greygoose, thanks for coming back to me. I will definitely get back to my GP. I did not actually think that my TSH levels were high as my GP said my levels were very good. My TSH levels have ranged from 1.62 to 4.61 over the last 2 years.


Sonyp, ranges vary from lab to lab. FT4 18 is commonly in range 12-22 and is normal, as is TSH 2.41 in a typical range 0.35-5.0. TSH >2.0 does indicate the thyroid is beginning to struggle to produce T4 but it will take a long time for it to rise over 5.0 which is when NHS diagnoses and treats hypothyroidism.


Clutter, thank you for the response and the links were very helpful.

1 like

You say you are taking 75mcg of Thyroxine. Most people find their symptoms only improve if their TSH level is kept down at or below 1. Do you have symptoms? If so then your doctor should increase your dose.

Do you have antibodies (TPO)? If so then you would expect your dose to be increased gradually as your thyroid is destroyed by the antibodies. A full replacement dose is usually between 125 and 200mcg, although it can be more than that. I have antibodies and have increased my dose from 75mcg to 150mcg over the past year or so to keep the symptoms at bay. I am comfortable with a TSH of below 0.3. Many people with hypothyroidism find they need to take more Levothyroxine (or whatever they are taking) in the winter.


Hi Eeng, I do have antibodies and I also am experiencing symptoms as well my body just aches constantly - ie joints, especially my hands. Have been tested for rheumatoid arthritis, but they say that my levels are ok, Another thing that went unexplained was swelling in my legs. First my left ankle and then a few weeks later my right calf. Both were extremely painful at the time and for no apparent reason. But as far as my GP is concerned I am in perfect health! So why do I feel so rubbish? I always feel like I am wasting their time as they say everything is fine. This is why I am trying to find out as much as I can and try to regain some kind of 'normality' back again myself as I don't think I will get much help from my GP.


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