Testing time advice.

[PrincessAnnie]

I’m going to book a test through medichecks today and I’m just wondering about the early morning testing.

I’ve opted for the clinic visit as I want a nurse to take it so I’m guaranteed a folate reading,what if I can’t get an early appointment,will it still be ok?

[SeasideSusie Remembering]

PrincessAnnie

It depends upon what you want from your test.

Early morning, fasting (water only), gives you the highest possible TSH which is important for some members when looking for a diagnosis of hypothyroidism or when their GP adjusts dose purely by TSH and they want an increase in dose or to avoid a reduction.

So advice here is always:

* Blood draw no later than 9am. This is because TSH is highest early morning and lowers throughout the day. If looking for a diagnosis of hypothyroidism, an increase in dose of Levo or to avoid a reduction then we need the highest possible TSH

* Nothing to eat or drink except water before the blood draw. This is because eating can lower TSH and coffee can affect TSH.

* If taking thyroid hormone replacement, last dose of Levo should be 24 hours before blood draw, if taking NDT or T3 then last dose should be 8-12 hours before blood draw. Adjust timing the day before if necessary. This avoids measuring hormone levels at their peak after ingestion of hormone replacement. Take your thyroid meds after the blood draw. Taking your dose too close to the blood draw will give false high results, leaving any longer gap will give false low results.

* If you take Biotin or a B Complex containing Biotin (B7), leave this off for 7 days before any blood test. This is because if Biotin is used in the testing procedure it can give false results (most labs use biotin).

These are patient to patient tips which we don't discuss with phlebotomists or doctors.

[PrincessAnnie in reply to SeasideSusie]

Thank you for your reply,I was just concerned as I’ve opted to go for a clinic visit that I won’t be able to get an early visit,I’ll try and get as close to 9am as I can.I’m currently waiting on a doctor calling me back to discuss recent bloods,it was a bad line,that was 10 minutes ago🙄

[SeasideSusie Remembering in reply to PrincessAnnie]

OK, so if the TSH is important then this graph shows you how it varies throughout the day and why we advise testing no later than 9am when you need the highest TSH, scroll down to first graph and you will see a rise between 8-9am then it lowers throughout the day and doesn't reach that level again until about 9-10pm:

thyroidpatients.ca/2020/07/...

[PrincessAnnie in reply to SeasideSusie]

I’ve had a quick look for Monday,tests not here yet I’m hoping it will be here tomorrow🙏as I have to wait until it arrives before booking test,the earliest I can get is 10.15.

[SeasideSusie Remembering in reply to PrincessAnnie]

Not the best time to get the highest TSH, you need 9am for that. But it depends what you want from the test results.

[PrincessAnnie in reply to SeasideSusie]

Tbh I’m more concerned with the T3 and vitamin levels,the doctor advised me that since I already had anti bodies that I would probably still have them,apparently they don’t use the names graves or hashimottos anymore as their old fashioned,it’s over or under🤦‍♀️

[SeasideSusie Remembering in reply to PrincessAnnie]

OK, so if you're not particularly looking for the highest possible TSH then the later appointment will be fine. If you take Biotin in any supplement then this needs to be left off for 3-7 days before any blood test. If you take any other supplements then don't take them on the day until after the test, and if you take iron tablets these should ideally be left off for a week.

[PrincessAnnie in reply to SeasideSusie]

I only take vitamin d which I usually take with breakfast so that won’t be until after the test,thank you so much for your help,the help and advice I’ve gotten on here has been invaluable🙏