Thyroid UK
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Blood test on NDT

So I am taking 65mg (1 grain) of Nature-Throid each morning. I am due to have a blood test to check my thyroid function, and was wondering what is the best time of day to have this. If I have the test early in the morning, before taking my NT, it will have been 24 hours since my last dose. Is that too long? I know you should leave 24 hours with Levo, but don't know if the same rule applies with NDT. I am using a private test, Medichecks, so I want to get it right!

6 Replies

Anything witht3 in it, like NDT, it should be 8-12 hours maximum since last dose when you do blood tests. Not sure the best way to juggle it... I take my NDT at bedtime so just take an hour it so earlier the evening before test.

X Linda 🙂


Thank you fibrolinda


It is recommended to leave 24 hours between dose and test and take it afertwards (that's if you take a morning dose). If you take an evening dose, miss this and take after test and night dose as usual.


Thank you for your reply shaws



If you leave 24 hours between last dose and blood draw you can add +20% to your FT3 result to estimate the normal circulating level.

1 like

Thank you Clutter


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