Log in
Thyroid UK
91,703 members106,003 posts

Optimal ranges of thyroid tests. Definitive answer please(I know it's a big ask)

I love this site and all of you are either on top of the knowledge tree or like me fighting through the forest. Please point me to where the optimal ranges can be found for Thyroid tests, bit D ferritin lepton and antibodies. I have underactive thyroid and Lupus. I have about 12 months or results in a beautiful table but haven't a clue what is high or low. All I know is I still feel 💩 on Levo but have a gp who has selective hearing. Thanks in advance.

2 Replies

Pooley66 There is no optimal 'range'. A range is a range, and each lab has it's own range, and a person's result falls somewhere within (or outside) the range.

Do you mean optimal level within the range? If so, there isn't a definitive answer because we all have a spot within the range where we feel best, as an individual. We are all different.

Generally speaking, it's said that the aim of a treated hypo patient is for TSH to be 1 or below or wherever it is needed for FT4 and FT3 to be in the upper part of their respective reference ranges when on Levo only.

For antibodies, the ideal is zero, but that rarely happens, so as low as possible is next best. As long as antibodies are under the figure quoted, eg <34 or <115, then that is considered negative.

Ferritin is said to be best half way through it's range.

Folate is said to be best at least half way through it's range.

Vit D, according to the Vit D Council, is recommended to be 100-150nmol/L or 40-60ng/nl.

B12 - minimum 550 according to an extract from the book, "Could it be B12?" by Sally M. Pacholok:

"We believe that the 'normal' serum B12 threshold needs to be raised from 200 pg/ml to at least 450 pg/ml because deficiencies begin to appear in the cerebrospinal fluid below 550".

"For brain and nervous system health and prevention of disease in older adults, serum B12 levels should be maintained near or above 1000 pg/ml."

If you want clarification of your results then post them for comment.


If you are taking levothyroxine or other thyroid hormone replacements the aim is a TSH of 1 or below. FT4 and FT3 should be towards the upper part of the range.

If you get copies of your blood tests results with the ranges. The ranges can inform you if they are low, middle or high.

It should be the same for all vitamins and minerals, with the exception of B12 which should now be nearer 1,000 to prevent dementia or alzeimers.


You may also like...