Do I need to stop taking NDT before having a blood test

[ArtyLouise]

Hi there, I'm due a blood test on Monday to check Thyroid levels and anti-bodies. Doctor is aware I'm on NDT and I've asked for Free T3. She's asked for T3 and says she doesn't know if it's 'free' as it's the only one she can order. I've also been told by a Naturopath that I ideally need to stop taking thyroxine for 48 hours before my blood test. Does anyone know if that is recommended? I have the test 2pm Monday so was thinking I'd not take it Sunday or Monday morning and start again Tuesday morning (or Monday after the test.) Thank you for any suggestions. Louise

[SeasideSusie Remembering]

ArtyLouise

Always recommended on here is to leave off Levo for 24 hours and NDT (or T3) for 12 hours. Any longer and you will have false low FT4 and FT3. So to get a result that shows your normal circulating amount of thyroid hormone, you should take your last dose of NDT 12 hours before your blood draw.

Also recommend is, if TSH is important when looking for an increase in dose or to avoid a reduction, to fast overnight (water allowed) and have the earliest appointment of the morning for blood draw, no later than 9am. This is because TSH is highest early morning and lowers throughout the day, and it can also lower after eating.

[ArtyLouise in reply to SeasideSusie]

Thanks Susie. my appointment is at 2pm on Monday and I normally take 90mcg NDT once a day on waking at 7am. It sounds like I shouldn't miss Sunday's dose anyway. Thanks for tip re fasting and blood tests - next time will do it first thing in the morning. Louise

[SeasideSusie Remembering in reply to ArtyLouise]

ArtyLouise

No, you take Sunday's dose, otherwise your last dose would be Saturday at 7am, blood draw Monday 2pm and that would be 55 hours.

If you take Sunday's dose at 7am then it would be 31 hours so still too long.

I would alter your timing for Monday morning's dose and set your alarm for early hours of morning, around 2am. That would be 12 hours and the maximum time recommend for last dose before blood draw. Any longer and you will get false low FT4 and FT3 as I said, and if your dose is increased because of those results you would most likely become overmedicated.

[ArtyLouise in reply to ArtyLouise]

Susie just another quick question - I normally take my whole dose in the morning. Is it better to split it over 24 hours? The only thing is I might forget! Also I know it's best not to take it near other supps. Thank you! Louise

[ArtyLouise]

Thank you Susie, that's really helpful!

[SeasideSusie Remembering in reply to ArtyLouise]

Sorry Louise, I misread your other reply (should have gone to Specsavers!). I can see now that you said you shouldn't miss Sunday's dose and I read it as should miss Sunday's dose. My apologies

[ArtyLouise]

Thanks Susie!!