blood test in afternoon do I take my levo or not?

Hi I am back at endos at 3.10pm for blood tests after 4 months being on levo 50 i have started to feel better but still have some joint paid and other symptoms. GP test showed TSH has gone down from 7.09 to 3.69 but i had taken my medication. Have read it masks results and pm not good time for bloods as I take in the morning should I take it or not? thx

17 Replies

  • Yes pm is not the best time for thyroid bloods, and yes don't take the days levothyroxine until after the blood test. Have your previous blood tests been done am or pm?

  • thanks for reply only had 2 first one was about 10am and second one was 8:30am

  • Jacqui,

    I wouldn't take my pill before and as Levo has a long half life you can easily take it after your appointment.

    Blood is better drawn in the am whilst fasting, when TSH is highest, so you reduce the risk of a doctor misinterpreting a low result (as too much meds).

    Post your results complete with ranges (numbers in brackets) for members to comment. Good luck with your appointment.

  • Thyroid blood tests are better done as early as possible as the tsh changes during the day. It should also be done when you have left 24 hours since your last meds, and about 12 hours after food, but you can drink water. You can eat and take your meds after the test. Having a blood test in the afternoon, when you have probably eaten during the day is pointless, can't you change it? It won't be a true reflection of your thyroid function. A tsh of 3.69 is still high and levothyroxine of 50 mcg is low. You still have symptoms and if you want your endo to increase your levothyroxine then your tsh needs to show high, as that is probably all he is interested in. I take it you have not had your t4/t3 done? They show how the thyroid is really working. If they won't do them then you can have them done with blue horizon medical.

  • thanks first test had FT4 11.3 and TPO antibodies 100.9 (positive) but last test when I rang GP they just said TSH was normal and 3.69 that's all the info i got! I thought i would have a more detailed blood test done today but they didn't take one!! as said could go on one GP did. am going to ask for a more detailed print out

  • Taking thyroid medication an hour or two before a blood test can skew the results. However, having the blood taken mid-afternoon is fine. TSH is higher overnight but unless you have the blood drawn before 9 am there is unlikely to be much difference in the TSH result. In any event you want a realistic result rather than attempting to get a distorted low TSH figure.

    See (click on the Endocrine Society box for the full text link). Note the scales - the fT4 and fT3 variations are small.

    I always eat or drink whatever I like on the day of a blood test, I've never noticed a difference. The only thing to watch out for is that if you are taking medication taking T3 (liothyronine or NDT) then you need to leave about six to eight hours from your last dose before taking the blood. This is so you get a realistic 'average' result as T3 has a short half-life of around a day or so (assuming you take T3 twice daily).

  • Well, I've noticed a hell of a lot of difference in other peoples TSH readings depending on whether they've eaten, and what time they do the test. Although, for myself, my tests have always been done before 8 and fasting.

    I think you're giving bad advice there, not just because the TSH is higher early in the morning, and before eating, but because lab tests should always be consistant if you want to be able to compare them - not one done in the morning, one in the afternoon, one after eating one not, and a variable time after the last dose.

    Following a protocol gives comparable results. And that's surely what we want, given that doctors only look at the TSH, and our health is at stake. Isn't it?

  • If you look at Fig 1 in the reference I gave above the TSH plot shows TSH is very stable between the hours of 10 am and 8 pm, within the accuracy of a TSH assay. TSH reaches a maximum between mid-night and 4 am and then falls rapidly between 4 am and 9am. The problem with taking blood before 9 am is that you will not know where on the steep gradient you are on that particular day, as your body clock varies from day to day, results will not be comparable. You will get a better (more accurate) TSH figure when the blood is taken during the day rather than early morning.

    This does raise the 'problem' that you will get a TSH figure that is lower than if the blood is taken early morning. This lower TSH is more accurate and more reliable but you may have to push harder for an increase in medication. I don't know what effect fasting has on TSH, I've never seen any trials. If it does elevate TSH it will give inaccurate results and I suspect noone is able to quantify the effects. Given that we do not usually fast all day it seems sensible to eat as normal. If you really want to get a false high TSH it is much easier to skip your medication for a few days.

    The danger with these tricks to elevate TSH is that the endocrinologists will get wise to them and make an allowance, rendering the efforts worthless and causing problems for the patients who do not distort the assay.

  • Endos getting wise to something? That's a joke! They haven't yet cottoned on to the fact that the TSH is a very unreliable test and shouldn't be used to dose by!

    You are unaware of any trials on the effect of eating on TSH? That surprises me, given the number of times it has been discussed on here. (Actually, it lowers the TSH, it doesn't raise it.) How about this :

    I really don't think you can say that getting tested early in the morning is 'distorting' the assay. It think that's rather a 'distorted' point of view. And, given that doctors consider the TSH to be the 'one and only' as far as tests are concerned, you can hardly blame people for wanting it as high as possible. And if it gets them a much-needed increase in dose, then so be it. If you are lucky enough to be on the dose you need and don't care about your TSH being low, so be that, too. But do be careful or you'll end up with a decrease in dose! And then you might understand what we're talking about...

  • Whoops! I must have seen the paper you quoted as I downloaded it two years ago, it may be in my pile of papers to be read.

    Unfortunately this paper is quite dreadful and should never have passed peer review let alone be cited on PubMed. (We all know peer review is political rather than scientific). The researchers measured TSH early morning and then three hours later after breakfast. We know TSH falls a lot between 8:00 and 11:00, there is no point comparing TSH at these two time intervals. This certainly confirms your comment about endos getting wise to anything.

    Another study found differences when the blood was taken at 9:00 and 11:00 (after breakfast) but not when the blood was taken at 9:00 on both occasions (before and after breakfast). Racking my brains I vaguely remember some study showing TSH does fall a little after a calorific meal. So perhaps a meal does lower TSH a bit.

    My argument for taking the bloods later in the day is that TSH levels out around that time, the result is more comparable. Also if the patient is subsequently goes onto T3 medication it allows the blood to be taken four to eight hours after the morning dose and so give a good average fT3 figure.

    I'm very keen on good science, it's the only way we can solve thyroid problems. The danger is that if doctors see the patients presenting with (false) high TSH readings it will reinforce their belief in TSH. They have to see symptomatic patients with low TSH figures who need a higher dose. This presents problems in the short term but it's the only way to get across the idea that the TSH is not always useful. Ultimately we have to find out why patients are symptomatic with normal TSH figures (my TSH was 1.0 when diagnosed).

  • But the OP isn't taking T3, so that arguement doesn't hold water. Besides, if we take T3, the TSH will probably be suppressed, anyway, and is of absolutely no interest.

    As to letting doctors see that you can still be symptomatic with a low TSH... You're a dreamer, Jim! They aren't in the least little bit interested in symptoms. They don't even know what the symptoms are! Nor would they have any idea that the TSH was 'falsely' high - although whether or not it is false, is a matter of opinion.

    We have to live in the real world, Jim, and do everything we can to get well - whatever it takes! If you have an intelligent, well educated doctor, then you are very lucky. That is not the case for the majority of people. We cannot go preaching 'good science' to people with mush for brains because their doctors dose by the TSH. We have to help them feel better any way we can.

  • I would just like to add, that médecine is a sexist industry. You probably managed to get diagnosed with a TSH of 1 because you are a man, and were taken seriously. That is not the case for most women.

    I had been complaining about hypo symptoms for over 50 years before I was diagnosed, but wasn't even tested, was just told I was lazy, stupid, greedy, should see a psychiatrist, learn to live with it, etc. One doctor told me I was hysterical, and another told me I was neurotic. When was the last time you were told you were neurotic? Never, I bet! So, please don't come here telling us women how it's done, you just have no idea!

  • A (very nice) endocrinologist said I couldn't be hypothyroid 'because my blood tests said so'. He was a decent guy but lacked scientific rigour (as most doctors do - they don't do logic). I was diagnosed by Dr Gordon Skinner.

    I'm sorry you weren't diagnosed, I suspect a female doctor would have behaved exactly the same (they certainly do now). Over 50 years ago the TSH wasn't relied upon. Women do get treated differently in many cases.

  • In my experience, female doctors can be worse than males!!!

    You were diagnosed by Dr Skinner... well, that makes sense. Unfortunately, he won't be diagnosing any more of us, poor man. We're left to the merci of the thyroid-illiterati! God help us all!

  • thx guys for all advice thought I'd update you. After not taking meds this am they didn't take any blood! Endo said could go on the results from GP test but has increased levo to 75mcgs and says they want TSH down to 2 but I'm in normal range which is 0.4 - 10 I think he said. I asked about tests for FT4 and FT3 along with all vitamin and minerals like B12 Ferritin Vit D etc he just said GP would have looked at these before going down thyroid route. Also said they probably didn't need to see me again and I could be seen by GP but when I had blood taken by nurse at GP's and asked about other blood test as well as TSH she said GP didn't do those so not sure where I stand now

  • The endo has fobbed you off and possibly 'fibbed' you off as well. It's possible that the 'endo' was a junior doctor, not a fully qualified endo? (You can check their status using the option on the GMC website ).

    The 'normal range' they quoted is for initial diagnosis of primary hypothyroidism, not for treatment. They feel that a TSH below 10 indicates the thyroid gland is functioning OK. (I don't agreee but won't get into the details of this). Generally most people with primary hypothyroidism do well with a TSH around 1.0 or 2.0. This is most people, not everyone, many need a lower TSH. It may seem a small difference if your TSH has come down from 7.09 but TSH increases exponentially as thyroid hormone levels fall. Thus, a change in TSH from 2 to 1 has a similar level of effect as a change from 8 to 4. Many doctors do not appreciate the mathematics of this relationship. Consequently they leave their patients undertreated.

    The GP can do most of the blood tests but even if they ask for an fT3 assay it will not get done, the biochemist at the lob usually overrules the doctor's request. The endo should be aware of this, hence my comment about you being 'fibbed' off. The GP should have checked the vitamin and mineral levels, the endo is right, but that doesn't mean they have.

    What to do next? See how you do on 75 mcg. If you are better but still not OK ask your GP for an increase to 100 mcg (give it a month to six weeks). Most patients eventually end up on a dose of around 125 mcg (but NOT everyone) so you may need another increase at a later date as your thyroid gland output fades away. If you don't get better and your GP is not co-operative contact the hospital for another endo appointment and be persistent.

  • thanks jimh111 he was junior Dr and defiantly felt fobbed off! I'm not one for taking up loads of Dr/GP time but I would have hoped at least one professional would have taken time to explain the condition and answer any questions I might have as well as giving me a prescription. It is quite complected for me to get my head around the maths of it all. I'm just pleased I found this forum so I have people like yourself who can help explain. after all how is anybody supposed to manage their condition if they don't understand it?

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