Thyroid UK
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Dosage advice? Changing from T3 only to T4 & T3?

Please can I have advice on how to change from T3 only to T4 & T3 combination?

I'd been on 150 or 175 Levo for decades, but in 2014 everything seemed to go wrong.

Loads of tests done; all inconclusive except last year - Vitamin D was 18 (15-30 deficiency) , but it is now 210 (>50 adequate, >220 high)

- Folate, ferritin, B12 all high in ranges.

- Nov 15 TSH 0.03 (0.35-3.5), T4 20 (8.0-21.0), T3 3.7 (3.8-6.0)

- May 1st stopped 175 Levo, started 20 T3. May 10th up to 30 T3. May 14th up to 40 T3.

- May 25th Results - TSH 0.2 (0.35-3.5) T4 <5 (8.0-21.0) Lab didn't do T3.

May 1st, my GP gave me 6 weeks of T3 after me pursuing it with 2 consultants. It's really started to give me my life back, after over 18 awful months. But... my GP has apologised that he is no longer allowed to prescribe it. I am in South Norfolk. I said I could buy it online from Europe, I think he was relieved! However we both think it's worth trying Levo & T3 combination to avoid the drops in levels I feel at times during the day on T3 only.

I'm currently taking 50 mcg T3. He suggested starting 100 Levo again and add in T3 slowly and adjust as I feel necessary. I guess I can keep taking current dose of T3 for a week or so while adding in the Levo again, then decrease the T3??

Is there any guide I can follow please? I'm a bit confused!! Thank you people!

2 Replies


If I'm right in assuming that you were on 175mcg Levothyroxine in Nov 2015 your results indicate that you weren't converting T4 to T3 very well.

Your results on 40mcg T3 in May 2016 are useless without FT3 result.

As a guide 25mcg T3 is equivalent to 75mcg Levothyroxine and therefore adding 100mcg Levothyroxine to 25mcg T3 might be satisfactory. I don't think you need to introduce T3 slowly as you are used to T3 only. It will take 7-10 days for the 100mcg Levothyroxine to be absorbed so you may want to continue taking 50mcg T3 for 5-6 days and reduce to 37.5mcg T3 for 2 days and then 25mcg T3.

I can't tolerate T4 only but I find that T4+T3 combination is a smoother ride than T3 only and I don't experience the dips that I sometimes experienced on T3 only.

If your GP can't order FT3 I would recommend you order a home finger prick test (including FT3) 8 weeks after being on 100mcg T4 and 25mcg T3. I think Blue Horizon Thyroid Profile 6 covers this.

Vitamin D 210nmol/L is high. 250nmol/L is approaching possible toxicity. Most people are comfortable around 100 so you could stop supplementing for a few months. VitD levels are expected to halve every 60 days after you stop supplementing. This would leave you in a good place to resume supplementing 2,500iu daily maintenance dose Oct-Apr when ultraviolet levels are too low to stimulate vitD.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Many thanks Clutter, I'd hope you'd reply! Thank you for these clear suggestions - I wasn't sure how to judge or time the changes in swapping my regime.

I was very disappointed having no T3 result, such a waste of time. I've taken 50mcg T3 for a couple of weeks now All I know is that I feel hugely better on T3. I can actually do things in the house which I've ignored for 2 years, and I no longer have those 'housebound' days. Thanks for recommendation re Blue Horizon - I'll definitely do check that out.

Realised my last Vitamin D test was December 15, and I talked to the lovely clinical scientist at the lab. She said I wasn't toxic at 210, but advised stopping supplements, which I did. Think I'll get another Vit D test too, to see how much I've dropped in the 6 months since stopping taking any.


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