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Thyroid UK
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Timing of T3 dose

About 8 weeks ago endo increased T3 from 20mcg to 30mcg of liothyronine. Took 20 mcg on waking then 10 mcg in afternoon. Got fed up of trekking upstairs to take mini dose so started taking the 10mcg at night. Found it suited me better. Taking in the afternoon I have disturbed sleep. Endo was horrified and said second dose shouldn't be taken after 3pm. Tried again but makes me wakeful. Have searched on here for info. I am now going to try taking one 30 mcg dose on waking.

Concerned that my endo thinks I take T3 and it instantly 'gees me up'. The only effect I have noticed is that I don't fall asleep by 2pm in the afternoon and it prevents episodes of vertigo - which I get if the dose is too low (and I also got after I quit taking T4). He snorts at the idea that thyroid treatment is related to vertigo and has contributed nothing to my health improvement other than switching me to T3 (after muscle pain problems on years of T4) for which I am grateful. I now function but I'd still prefer to live!

Is it normal for T3 to have such a slow effect? I have a blood test coming up should I not take the T3 that day?

5 Replies

I had a blood test last week when I wasn't expecting one.

I don't usually take my T3 before testing (or my T4 the night before either) but did on this occasion and my T3 level and TSH level indicated I was being over medicated. GP agreed to leave dose alone until I had another blood test without taking T3 until after test. I said I thought it was inaccurate due to T3 being spiked in the blood and not yet reached the cellular level where it is needed.

Hope this helps you decide whether to take it or not. X


Thanks. Will follow Clutter's advice and have the test 24 hours after my last dose.


Loueldhen, many people can't sleep unless they take some T3 at bedtime. Take it at the time which suits you best. I take 20mcg on waking and 10mcg at bedtime.

T3 levels are highest around 02.00-03.00am so night time dosing makes perfect sense to me. Have a look at the graph in this link healthunlocked.com/thyroidu...

The European Thyroid Association says In order to mimic the circadian free T3 rhythm, the larger of the two daily doses of L-T3 might be given at bedtime.


Endos have some peculiar ideas about what a medication can and can't do. If T3 helps reduce your vertigo then it is likely your vertigo is related to thyroid levels. Other members have found it be so.

T3, like T4, is not an instant fix. It takes a few weeks for it to metabolise, raise FT3 levels and start working on symptoms.

Ideally leave 24 hours between last dose and blood draw. 12 hours is the minimum if you are on T3 only.


Thanks for the advice and data. Nice to know there's still some room to experiment.


Hi, just to say I take just over 30mcg of T3 once daily in the morning. I feel well and energetic and have had to adverse affects from T3 at all. I have no 'swings or roundabouts' with T3 just a smooth transition very unlike being on levothyroxine only.


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