Thyroid UK
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Please advise! T3 for 7 days, dosage OK?

My GP gave me T3 a week ago, after a veiled comment re a T3 trial from endo. I'd been on 150/175 levo previously. GP said to take 10mcg T3 twice a day, and said to stop levo. I had 2 days when my heart seemed a bit fast sometimes, but no side effects since. I assume this was because I still had levo in my system?? I've had huge exhaustion for 18 months.

This week I haven't felt 'normal', but definitely less bad!! But will the levo now be leaving my body? Do you think I'll need a higher dose of T3? How long does T3 take to work?

March test - TSH 0.04 (0.35-3.5) T3 4.2 (3.8-6.0) T4 21 (8.0-21.0)

My GP is phoning me tomorrow to discuss. Help please, not sure about doses etc!

5 Replies

Hi TarjR

Your doctor has erred on caution as many don't know best how to prescribe T3 but at least he has which is good news for you.

First he stopped levothyroxine 150/175 and provided 20mcg daily of T3. The only problem I can see that he has reduced your thyroid hormones drastically, i.e. 20mcg of T3 is equal to around 60mcg /75mcg of levothyroxine.

What is usually done is reduced levo by 50mcg and add 20mcg T3.

T3 is absorbed into our body quickly - within 3 or 4 hours, I believe. It has to saturate our receptor cells and then its 'effect' lasts for between one to three days. We have billions of receptor cells and T4 (levothyroxine) is inactive and its purpose is to convert to T3 but doesn't always do so efficiently.

If your GP hasn't tested your B12, Vit D, iron, ferritin and folate ask for these as we can be deficient.

When your next blood test is due it should be the very earliest possible and don't eat before it. Also allow about 24 hours from your previous dose of hormones and take it after blood test. This allows the TSH to be at its highest as that seems to be all the pay attention to and isn't the best way for a patient to recover.

You can say you have taken advice from NHS Choices


Thank you Shaws. This is useful info. I'll see what my GP says.. he knows me well, and is usually easy to talk to. He just wants me to be well again. My daughter is expecting twins in a few weeks, and I just want to feel well enough to enjoy them, and to help her too.

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As I commented previously 20mcg T3 is equivalent to 60mcg Levothyroxine and your GP should have prescribed 3 x 20mcg daily if s/he wants you to stop 175mcg Levothryoxine.


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.

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Thank you Clutter. Yes I remember your previous info. Today I was trying to see if anyone else had been swapped to T3 alone Maybe I didn't make that clear, as I was in a hurry! I really value all these comments, and this forum.



I've been switched from T3 to Levothyroxine, and Levothyroxine to T3.  I was switched from 60mcg T3 to 200mcg Levothyroxine, and a few months later, from 150mcg Levothyroxine to 60mcg T3 and back again to 150mcg Levothyroxine.


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