Thyroid UK
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I'm very confused about timing of the TSH tests. When is the best time?

I've read several things about the time this should be done.

My body feels ok first thing in the morning and even better an hour after taking my levo. By 1pm I'm slowing down, and if its a work day, by 3pm my muscles are screaming at me, my joints are seizing up and I can hardly walk or think. I'm in bed by 6pm.

Today is not a work day, so after being in bed from 3pm, I'm ok at 7pmas I've just got up.

My understanding is that TSH is higher in the morning and drops as the day goes by - but why do I feel ok in the morning and so ill in the afternoon? Wouldn't the reading be more accurate in the afternoon, when I'm really struggling?

6 Replies

Can't remember if I ever pointed out this blog:

Go to the paper and look at the graphs. (Obviously this is "typical" and your patterns might be slightly different.)

The point about testing at 08:00 (or as early as possible) is not that it will actually catch the peak (which is more likely at midnight and a bit after), but it is better than the afternoon trough.

Remember that FT3, FT4 and TSH have their own rhythms.

But it makes me think that you are simply running out... And therefore might need a higher dose?

Or one or more of the other things people often suffer from.



Thank you - the graphs are very useful - I'm a visual learner!

They also show clearly how much each person can vary from another.

I'm arguing GP for a higher dose although after being here for a few months, I was anticipating problems. I eventually got the go-ahead for another test - but I had to point out I'm becoming incompetent at work before GP agreed to this further test - a higher dose (up to 75mg) got an outright 'no'. Also testing for other issues got a 'no'.

I'll do the test on Monday and see what this is before planning my next move.

Thank you for your help.


For things like this, so long as they don't confuse, graphs are wonderful! :-)

Pleased you picked up the variation between people.


I found that although TSH tends to be higher in the morning and lower in the afternoon, the same is not true of fT3 and fT4. I have found these to be lower in the afternoon, so this maybe why you are running out. Totally Gree with Rod that you may need an increase of T4, or the addition of some T3. Xx


Thank you.

I think this is the case and since I seem to do well on T4 until I run out, you'd think that a small increase in the dose wouldn't be too much to ask for.

Shouldn't my morning dose be enough to last at least 24 hours?


Yes it should if it is high enough ...


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