Best time of day for blood testing

[Beau55]

Hi everyone,

Just wanted to ask a quick question before I next get my blood done. I know it’s best to get your blood done first thing and fasting to give highest TSH reading but is this also the time with the lowest T4/T3 results?

I am interested to know which time of the day T3 is at its lowest and if anyone happens to know!!

Thanks I advance

Sarah

[Lalatoot]

This article deals with the circadian rhythms of TSH and thyroid hormones thyroidpatients.ca/2020/07/...

[ Space added between "hormones" and "https" to avoid possible issues with link. ]

[Beau55 in reply to Lalatoot]

Thank you this is very helpful! It looks like T3 is highest earlier in the morning and drops throughout the day!

[Lalatoot in reply to Beau55]

Yes it peaks 4am ish. this is why some folks take a dose of lio T3 at night - to get that peak. Our body works hard during the night and needs thyroid hormones to let our brain work its filing and processing and our gut work its "magic"!

[humanbean]

Since doctors usually only take TSH seriously, the levels of Free T4 and Free T3 rarely have much impact on their decision-making about thyroid disease. (Although they really should make a difference!)

This ancient thread on the subject may be helpful :

healthunlocked.com/thyroidu...

The graphs come from this research paper :

academic.oup.com/jcem/artic...

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[Beau55 in reply to humanbean]

Thank you!

I am using a doctor from the thyroid uk list who has said she ignores the TSH but wants to see what my T3 is and bass it off that- however I’m not sure what time of day gives the best reading for this only when is best for TSH!

[humanbean in reply to Beau55]

Well, based on those graphs if I've read them right, lowest T3 occurs around 3.00 pm. But that also coincides fairly closely with lowest TSH.