Gap of more than 24 hours between Levothyroxine and thyroid blood test

Hi there, I take levothyroxine during the early hours when I wake up between 2am and 4am, my blood test is booked next month for morning 11.00am. I will take the levothyrioxine after the blood test, but there will be a gap of more than 24 hours, less than 48 hours when last dosage taken. Is that okay? I could not get an earlier appointment.


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15 Replies

  • Peony88 I take my Levo roughly the same time as you, it can be anywhere between 2am ish to 6am ish. I am doing a fingerprick test tomorrow, and as always I am adjusting the time of my Levo so that it will be 24 hours.

    I took mine this morning at 8.30am instead of in the middle of the night, and I am splitting my T3 today so that I get half my dose 12 hours before my test, I usually take that around 7-8am in one dose. I took half at 8.eo this morning and will take the other half at 8.30 this evening.

    If you want to be able to compare results accurately then you should make sure the conditions are the same every time you test.

    You really should change your appointment for one no later than 9am particularly if you are looking for a high TSH to avoid a reduction in Levo or wanting an increase.

  • Thank you, I could not get an earlier appointment, I will check to see when the next availability for an earlier appointment before 9am, there computer systems does not allow to check further than 2 weeks. If I am not able to get an earlier appointment I will keep the 11.00 am

  • Hi Seaside Susie, I tried to change my appointment to earlier appointments before 9.00 am. All booked up. I will have to keep the 11.00 am appt. Should I take the levothyroxine the day before in the morning at 11.00 am? They never see the patients on time even though we arrive there on time.

    Thanks for your help. For future blood tests I will bear in mind to get much earlier appointment.

  • What are you looking for from the blood test? If you're looking for an increase in Levo then you need the highest possible TSH. Blood drawn at 11am will give a lower TSH than blood drawn at 9am.

  • The Doctor needs to to get me on the correct dosage again, a year ago my TSH was within the normal lab range. This year during my annual check blood test showed that my TSH is 7 and therefore not in the normal range. So the levothyrioxine was increased from 75 mcg to 100 mcg. Now I am due for a follow up blood test to check where my levels are. Hopefully within normal range and and I will insist that it should be below 2 or 1. If not medication may need to be increased. The GP said anything below 4 is within normal range.

    Thank you so much for your reply. Lower TSH below 2 is what I am aiming for.

  • So really you want to avoid a reduction or you're looking for an increase.

    As your GP has said that anything below 4 is normal, you may have a hard job trying to get him to accept below 2.

    Don't forget to take how you feel into account, you can't just go by the numbers.

    Personally, I would rearrange the appointment. I know you'll have a wait but I wouldn't risk it. You need the same conditions each time you are tested to accurately compare numbers if that is what your GP insists dosing by and your TSH will be highest early in the morning after an overnight fast and no Levo for 24 hours.

    I have been dodging retests for 3 years as my GP only goes by TSH and mine is always suppressed regardless of dose of meds. I was at the surgery yesterday with the respiratory nurse for a check up and she said I was long overdue and could she do a blood draw there and then. It was 10.20am and I refused. I said that I know there is a circadian rhythm with thyroid hormones and so that my results can be accurately compared I like them done as early as possible each time. So she's booked me in for 8.40am and I have only had to wait two weeks for that. Trouble is, I know my TSH will be suppressed (I've just done a blue Horizon test) and I know I will have a battle on my hands when the result is received.

  • Thank you. Your have been so helpful and I am so grateful. Your right I should delay the test to a later date for an early morning one. I wish you well, with all good wishes, enjoy your weekend.

  • Hi SeasideSusie, I hope your keeping well and all is good. I just want to double check with you as a cancelled blood test appointment has become available for this Friday morning at 8.45am, which I have accepted. If I normally take my levothyroxine between 2am and 4am should I take it later on Thursday morning at 8.45 am to allow the 24 hour gap between levo and blood test. Does it have to be 24 hour gap or can I leave a longer gap say if I take levo on Thursday at 6am? Thank you again for your help.

  • As you're looking for as high a TSH as possible, a few extra hours won't make much difference really, so it's up to you. You could take your Thursday Levo at 6am if that suits you, then on Friday take it after the blood draw.

    A much better time for your blood draw :)

  • Why are you doing this? The extra 24 hours means your fT4 will record about 90% of the real value and the TSH will be out to a larger extent. Just a few hours between taking levothyroxine and drawing the blood is sufficient to avoid any assay interference.

    Do you naturally wake up between 2 am and 4 am? That would make me so tired. Maybe by taking your levothyroxine at that time you are training your body clock to wake you up when you might enjoy a good night's kip, at least for some nights.

  • Thank you for your response. I have to get up to use the bathroom and then I go back to bed. This is more convenient time for me take it, as I do not need to worry about having to leave one hour gap before having tea and cereal with milk in the mornings, if I took the levothyroxine. Also it will not interfere with nutritional supplements.

    The receptionist at the surgery suggested not take take levothyroxine before blood tests and to take straight afterwards.

  • Makes sense. Levothyroxine is absorbed in about three hours but as you will be sleeping I'd leave five hours to be on the safe side. So if the blood test is after 09:00 you can take the levothyroxine anytime before 04:00 (just don't call me to tell me you've taken it !!!).

  • Dear peony, I feel much better omitting anything with milk in..full of hormones suitable for calves you need to grow fatter quickly ?

  • Thank you Gingergirl1948, I am a vegetarian, excluding also eggs and fish from diet . Have been since birth. I take organic milk for B12 and Calcium. Hopefully organic milk contains less of the hormones. I did at one point consider many years ago to become a vegan, tried it for a month and my nails became brittle and bones started to ache. I am pleased that you feel much better.

  • I included more nuts and greens, tahini etc. Nails. Stronger than ever. I saw babies removed from mum cow ...that's what I turned vegan. I am so fragile around cruelty.

    Exhale and be happy.

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