Thyroid UK
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How do you work out the t4/t3 conversion ratio? And comments on results please


I had some new results come in - be good to get your comments - see below.

Also, how do you work out the conversion rate for T3? Do you divide the Free (T4) by the Free (T3)?

I have been supplementing Vitamin D for about 8 weeks now with 5000Iu every day yet this has dropped from 47 (same range) at the last test of about 8 weeks ago. Do Vit D levels move up and and down relatively quickly? Do I need to up my dose?

Symptoms wise I have been feeling better for taking supplements (all the recommended ones). Only thing is my hair is falling out in handfuls still.

Lastly, I get way too 'jittery' when taking Vit B12 and B complex. My head races and i feel anxious. Should I just reduce the dose?

Thanks, as always!

CRP 0.10 (<5.0)

Ferritin 91.5 (20-150)

TSH 4.49 (0.27-4.20)

T4 Total 100.6 (64.5-142.0)

Free T4 14.36 (12-22)

Free T3 4.57 (3.1-6.8)

Anti-Throidperoxidase abs 136.3 (<34)

Anti-Thyroglobulin Abs 25.7 <115

Vitamin D 38 (<25 - >175))

Vitamin B12 388 (<140- >175)

Serum Folate 45.80 (8.83-60.8)

5 Replies

Forget ratios, they're really not very helpful. The ratios are what euthyroid people have, they don't necessarily translate to people with hypothyroidism.

What you need to look at is the positon of your result in its range. If you are converting well, the FT3 will be higher in its range than the FT4 in its range.

Your FT3 is just under mid-range. The FT4 is quite a bit below mid-range. So, you are converting well, but you don't have enough to convert. You need an increase in dose. And your TSH backs that up. It's much too high for someone on thyroid hormone replacement. You'd probably feel a lot better if you were taking enough to bring your TSH down to one or below. :)


misha008 Yes to get the ratio you divide FT4 by FT3 and yours is a very healthy conversion rate of 3.1 : 1

I wonder if your Vit D level has dropped because it's now winter with much less sunlight available and, of course, we can no longer go out with bare skin to absorb the natural Vit D. You could increase your dose to maybe 7,500iu daily for a few weeks, then back down to 5000iu daily and retest in the spring. Are you taking K2-MK7 and Magnesium alongside your D3? They're both very important co-factors.

Your ferritin is good so that shouldn't be contributing to your hair loss, that may be down to you not being optimally medicated.

I wonder if there's something in the B Complex that you're reacting to. I can't help with that as I've not had a problem. If no-one else offers any suggestions you could make a new post tomorrow purely to ask about that.

You need an increase in your Levo, your TSH is over range and your Free Ts too low. The aim of a treated hypo patient is for TSH to be 1 or below or wherever it is needed to be for FT4 and FT3 to be in the upper part of their respective reference ranges if that is where you feel best.

Are you addressing your Hashi's by being gluten free and supplementing with selenium?

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Conversion rates depend of what you are medicating, genetic impairments and state of health.

There is no hard and fast rule as we are all different and blood serum results are not always indicative of what is happening on an intra cellular level.

Any issue//condition such as a pituitary problem, unbalanced TBG, elevated cortisol, excessive oxidative stress and certain mineral deficiencies (ie selenium) will effect how thyroid hormone converts. Also gut dysbiosis (as 20% of thyroid hormone is converted in the gut) and thyroid receptor issues which will eventually encourage too much bound thyroid hormone in the blood stream (so unavailable for use).

Any conversion issues are generally not recognised by the medical profession.

TSH is high and T4 and T3 still low. What dose Levo are you now medicating ? ? ..TPOAb are over range. Are you eating gluten free ? ? ..

Vit B12 can be quite powerful in giving you a lift. Perhaps you should introduce in a smaller dose. I don't know about Vit D dropping after supplementing...others will comment.

Supplementing selenium is known to help with T4-T3 conversion and reduce TPOAb.


selenium & Thyroid Hormone Metabolism


Selenium Decreases TPOAb


Hi when I take B12 and B complex my heart races very fast . So I have just been taking B12

So same As you but can't help more other than I get the reaction as well.

Hope more help soon



It may simply be that you are experiencing detox symptoms as the Vit B12 starts to repair damage and stimulate the nerves.

It is important to keep Vit B12 and folate balanced, and iron optimal, as they all work together and having deficiencies in one can prevent the others from doing their jobs properly.

Methylcobalamin is a better form of supplemented Vit B12 as is pre-methylated, meaning it's ready for your biochemistry to put to immediate use.

Supplementing Betaine HCL with pepsin (with food) will also help Vit B12 absorption and form essential 5-MTHF (enzyme required for properly nutrient utilisation) and produce SAMe.

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