Taking last dose of levo prior to thyroid blood test

[Caroline888]

SeasideSusie

Hi Susie, I've seen several times that, like me, you take your Levothyroxine in the small hours. I usually take mine around 3 a.m.

What do you do about making sure you take your last dose of levo just 24 hours before thyroid blood tests? Do you adjust the timing of your doses in the run up to the blood test, taking your dose later each day, or just go on as usual til the last day before the test when you then delay your dose, normally taken between 3 and 6 a.m in your case, until say 9 a.m. if your blood draw is 9 a.m. the following day?

I would be so grateful for your advice.

Best wishes

Caroline

[SeasideSusie Remembering]

Hi Caroline

Yes, normally I take my Levo and T3 any time between 3am and 6am.

When having a blood test I know that I'll be doing it at 8.30am if it's one I'm doing myself, soI change the timing the day before. So I take my Levo at 9am (I also alter how I take my T3). If it's a test at the surgery I do the same but can't control the exact timing of the test, it's usually by 10.30 at the latest.

[Caroline888 in reply to SeasideSusie]

Thanks Susie for your quick reply.

So I don't need to adjust the timing of my doses in the week preceding the blood test, just delay it the day before the test. Is that right? I was thinking maybe the big gap just before the blood draw would affect the test significantly. Not so?

[SeasideSusie Remembering in reply to Caroline888]

So I don't need to adjust the timing of my doses in the week preceding the blood test, just delay it the day before the test. Is that right?

Yes, that's correct.

The reason for the 24 hour gap between last dose of Levo and blood draw is because if you test too soon after a dose the result will show the level of FT4 as a false high because it will measure the dose just taken. Levo peaks in the blood around 2-4 hours after ingestion then gradually lessens as it starts to move from the blood into the cells. So a 24 hour gap is said to give more of a normal circulating hormone level.

[Caroline888 in reply to SeasideSusie]

Thanks Susie. That’s great!

I’ve been struggling to take my levo an hour later each night to reduce the gap and it’s not made for a good night’s sleep😟.

Thanks again. You’re a star!

Best wishes

Caroline

[ChloeL934 in reply to SeasideSusie]

Hi, I started taking levo in December. 50 one a day. That was fine, my levels went back to normal, however recently I’ve been getting the feeling of my heart beating too fast. I had another blood test done and the doctor said it was a little high, I wasn’t made aware that I shouldn’t take the Levo before, my last blood test I took the tablet then went to get my blood could that be the reason for the high reading? X

[SeasideSusie Remembering in reply to ChloeL934]

my last blood test I took the tablet then went to get my blood could that be the reason for the high reading? X

Yes, if you read my reply to Caroline you will see I said taking Levo before a blood tests gives a false high level:

The reason for the 24 hour gap between last dose of Levo and blood draw is because if you test too soon after a dose the result will show the level of FT4 as a false high because it will measure the dose just taken. Levo peaks in the blood around 2-4 hours after ingestion then gradually lessens as it starts to move from the blood into the cells. So a 24 hour gap is said to give more of a normal circulating hormone level.

If you start a thread of your own and include details of your test results (with reference ranges) for TSH, FT4, FT3 and if you have the also include Thyroid antibodies, Vit D, B12, Folate and Ferritin, then members will respond.

[Valeriu]

Yes I was told your last dose has to be 15-18 hours before the blood test; So, last time I had to take my NP at 5pm (instead of the 2pm) so I had again 17.5 hrs after NP and before the Thyroid monitoring test. Good LUck !

[Caroline888 in reply to Valeriu]

Thanks, Valeriu, for taking the time to reply to my post. I did know I had to take my last dose of Levothyroxine 24 hours before the blood draw. My concern was about the gap between doses when I had to delay my usual dose from 3 a.m. to 9.00 a.m. on the day before the blood draw to achieve the 24 hour interval. However, SeasideSusie has assured me this is not significant.

Thanks again for your input. It's all so very complicated isn't it? Thank goodness for this site.😊. I don't know where I'd be without it!!

All the best

Caroline

[ChloeL934 in reply to Valeriu]

Sorry to jump on the post, my doctor has told me to take the Levo before my blood test? Is this wrong x

[Caroline888 in reply to ChloeL934]

Yes it is wrong. See SeasideSusie’s reply above to my post.

These doctors know nothing!

All the best

Caroline

[ChloeL934 in reply to Caroline888]

I know it’s so frustrating. Thank you x

[Caroline888]

Thanks for replying to my post.

Actually the delay until after the blood draw is not what was concerning me but the fact that, the day before the blood draw, I have to delay my usual dose of levo taken at 3 a.m. until 9 a.m. so as to achieve the required interval of just 24 hours before the blood draw. I was concerned that this would significantly affect the results of my blood test but have now been assured by SeasideSusie that this isn’t the case.

Thanks again for taking the time to reply.

Best wishes

Caroline