Best time of day for thyroid blood test

[Verity72]

Please would you advise how the TSH levels vary during the day and when is the best time to have a blood test. Is it best to fast? And what about taking thyroid meds/glandulars the morning of the test? Many thanks.

[SeasideSusie Remembering]

TSH is highest very early in the morning and lowers throughout the day. I don't have the link that shows the graph, and can't remember who has.

TSH also lowers after eating.

Best time for thyroid blood tests therefore, if TSH is important to be high (in the case of diagnosis, looking for an increase in dose of Levo or to avoid a reduction) is the very earliest appointment of the morning that your surgery does blood draw, preferably no later than 8.30-9.00am. Also fast overnight although you can drink water.

Leave off Levo for 24 hours, take after the blood draw. Any thyroid meds containing T3 (NDT or synthetic T3) should be left off for 12 hours. Take them too near the blood draw and you'll get high FT4/FT3, take them longer than the 24/12 hours away and you'll get false lows. Thyroid glandulars I would suggest treating the same as NDT ie leave 12 hours.

[Clutter]

Verity72 and SeasideSusie ,

healthunlocked.com/thyroidu...

[SeasideSusie Remembering in reply to Clutter]

Thanks Clutter (I'll save that)

[Verity72]

Thank you very much for that info.