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Thyroid UK
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Blood tests and night shift workers

Hi everyone, I'm Jacqui. I just recently found this forum and wondered if anyone could help me out with a quick question. I know that TSH tends to be higher in the morning and this is the best time to have the test done but would this still be the case for someone who does constant night shift?

I tried googling it but couldn't find a whole lot of clear info and am still unsure how much reversed sleep patterns throw your body's natural circadian rhythm out of whack.

In my case would it be better to book an afternoon appointment for after I'd slept for a few hours, or are TSH levels higher during the night regardless of when you sleep?

8 Replies

Welcome to the forum, Sapphiari.

It doesn't matter what time you sleep, TSH and FT3 follow circadian rhythms. See the graph in this link healthunlocked.com/thyroidu...

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Hi Clutter, thanks for your reply. The graph is very helpful. I'll arrange for my blood test to be done in the morning.

The last time I had my levels checked, the test was done in the afternoon. I'd just come back from a holiday, so had been sleeping through the night for once. I'd also taken my medication that day, which I now realise was all wrong.

Anyway, the results came back as TSH 3.63 and T4 17 (sorry, don't know the reference ranges) and the doctor refused to up my meds from 50 mcg levo on the grounds that my thyroid levels were now 'completely normal' and couldn't be the cause of my never-ending list of symptoms.

Obviously I disagree and wanted to get the test done right this time!


Sapphiari, Leave 24 hours between last dose and blood draw which should be a fasting test (water only) as TSH drops after eating and the earliest appt you can arrange when TSH is highest.

Most people are comfortable with TSH around 1.0 with FT4 in the upper quadrant. Read Dr. Toft's comments in Treatment Options thyroiduk.org.uk/tuk/about_... Email louise.warvill@thyroiduk.org.uk if it would be useful to show your GP a full copy of the Pulse article.

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No wonder you feel unwell. A TSH of 3+ is awful. Email louise.warvill@thyroiduk.org.uk and ask for a copy of Dr Toft's Pulse online article. Question 6 gives you info and discuss with your GP for a rise in medication (or the addition of some T3). An excerpt:


T3 doesn't convert as T4 does. T3 is active and goes directly into our Receptor Cells (we have billions) and there has to be sufficient to saturate the receptor cells. Of course, you increase gradually after you've switched from T4 to the equivalent in T3.


Moreover, the dose he prescribed, 0.05 mg, is extremely small. It’s so extremely small that it's highly unlikely you'll benefit from it in any way no matter how long you take it. On the other hand, that small a dose may actually slow your metabolism more and worsen your symptoms. Perhaps this has happened, in that you say your symptoms have worsened since you started taking Synthroid.


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I had no idea TSH dropped after eating. I'll be sure to get the earliest appt possible and skip brekkie!

Hopefully this test will show a truer picture as even when my results were TSH 2.5/T4 19, I felt better than I do now.

I've just emailed Louise about the article.

Thanks again for your help.


The clue as to why you felt better is the T4 levels. You said you felt better with a higher T4 level. This would have led to a higher T3 level. albeit a small difference. What would, of course, be wonderful would be if you could have your T3 level tested!

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Hi Shaws and Marram :)

I certainly don't feel well at all with these levels. No matter how long I sleep, I still need ridiculously strong coffee (not at the same time as meds) just to keep going. My skin is dry and flaky, nails are peeling, hair is getting thinner by the day and my menstrual cycle is crazy. I'm also freezing cold when everyone else thinks the temperature is fine, or even too hot. After being in someone else's house, the first thing I do when I get in is go and sit in front of the fan heater in my bedroom to 'thaw out'.

Shaws, I think you could be right about the low dose making everything worse. My GP actually started me on 25 mcg last year, and for a while I felt a little better, then my symptoms returned and my hair was coming out so much, the shower drain was clogged every time I washed it.

I was retested and the results were TSH 9.5/T4 14. Unbelievably, the receptionist at the surgery told me over the phone that the doctor was quite happy with my results for now and I was to be checked again in 6 months!

I've no idea why he would be 'quite happy' with these levels as my TSH was never as high as 9.5 before I was on meds - since age 21 (I'm 37 now) I've has TSH levels that varied between 3 and 6. Despite numerous health issues and a family history of thyroid disease, I was always told that wasn't my problem, as the level of thyroxine in my blood was normal and that they'd just 'keep an eye on me'.

Anyway, I managed to persuade my GP to give me a trial of levo, then up my dose to 50 mcg, but now I feel like I'm pushing my luck with him. There are only two at the practice and he's been a lot better than the other one, who only wanted to throw antidepressants at me.

I don't think I've ever had my T3 level tested. As far as I know it's not something they routinely do at this practice.

Funnily enough, the first thyroid test I remember having done at age 20 showed the opposite of what I have now. My TSH was low normal and T4 was slighlty above the reference range. This was at a different GP surgery and the doctor said not to worry about the result - and I didn't as I felt fine (wish I could say the same now!)

Sorry for such a long-winded post!

Thanks to everyone for your helpful replies.




My husband was firmly told shift work was a no no for thyroid patients

easier said than done of course

I would think after waking from sleep would be best time for you


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