Confused about blood test advice. GP or the empirical?

Hello, I am a bit confused by the advice about having a blood test:

The advice on here is: Leave thyroxine for 24 hrs before test.

GP advises me TAKE the thyroxine as normal (at 6 am on an empty stomach) and then have the test as will show true levels of absorption/effect etc.

I am booked in for 11:40 on Monday coming. Any ideas or advice please?

My GP suspects some of my symptoms presented may be angina, liver related, sarcoidosis or thyroid, he has given me a sublingual spray, Glyceryl Trintrate, which is an angina drug. My symptoms seem to be that of those four things! (I have a complicated medical history as I have a genetic fault that is very rare one of 5 in UK.)

16 Replies

  • The doctor can advise as he wishes. They usually go only upon the result of the TSH. It is highest early a.m. and prevents GP reducing our dose to try to fit TSH within the 'range'. In fact we feel best if it is 1 or lower. It drops anyway, throughout the day, highest a.m. and reduces all day.

    Taking hormones before the blood test will also skew your results as they will appear 'optimum' as we've just taken them a couple of hours before.

    You have to make whichever choice you decide. The earliest possible appointment is best for us if we do not want unnecessary adjustments due to skewed TSH or hormones results.

  • Signs/symptoms of hypo:-

    Blood tests are secondary to how the patient feels. What we want is relief of All Clinical Symptoms we have, not just to have our blood results somewhere within the 'ranges'.

  • That was the chart I looked at before posting, I ticked many boxes. Thanks. He was happy that I had self increased my Levo to 100 from 75. 'If it makes you feel better that is good'. Need to make a decision, but erring on your advice: 24 hr fast of drug.

  • You can always fast next time and take levo afterwards. :) It is a learning curve, no doubt about that.

  • I am hypogonadic (genetic fault, thanks) and have fought for many many years not to be 'in the range' for testosterone! An Andrologist soon resolved that, I was severely under-dosed, and he used my 'wellness' as a marker rather than little numbers on a page.Thanks.

  • It should be the same with thyroid hormones i.e. how the patient feels and not the numbers on results?

  • Do you have any results of thyroid tests that you could share with us ? - results with ranges ? What dose are you on ? If your TSH result is low in range then your GP may not give you the increase in dose that could help you to feel better and relieve some of your symptoms.

    I have read about the considerable difference in the TSH based on the time the test was taken. The choice as shaws says - is yours - but most people are wanting more hormone rather than less :-)

    Angina - I expect you have read about the connection with the thyroid - both too little and too much thyroid hormone is not good for the heart. Apologies if that condition is connected to your rare genetic fault - if so please ignore me !

  • The genetics confuse most doctors and myself. Too much fog. My last 'good' test was in July 16 and I posted them here and it was advised that the figures were right for the time but probably not now with the increase in symptoms. Thanks.

  • Archaepon,

    Levothyroxine can peak in the blood up to six hours after taking a dose which is why members are advised to take it after their blood draw. TSH is highest early in the morning and will be quite low around 11.40. You might want to consider rearranging your blood test so that is prior to 9.00am. Some GPs will consider patients are over medicated when TSH is low and will reduce dose.

  • I cannot rearrange the app as it is the only one available next week, a cancellation. I need to resolve my condition. The blood test will take in any heart or liver problems too.

  • Archaepon

    In my opinion, your GP is misunderstanding the point of the blood test. The test is not about checking the absorption of levothyroxine, but to find out how much levothyroxine you need to be taking to get you comfortably through a 24 hour day.

    Leaving a 24 hour gap between taking thyroxine and getting blood drawn, illustrates how low (or high) your blood levels are *without* a day's worth of medication. This is what you need to know.

    e.g. If blood level of FT4 is very high 24 hours after your last dose, then that could indicate that the dose is too high. If blood level of FT4 is very low 24 hours after your last dose, then that could indicate your dose is too low. Either scenario may indicate a need to change the dose, but symptoms should also be taken into account to arrive at a meaningful conclusion.

    If your GP is only testing TSH, then it's the opposite way around... very high TSH indicates too low a dose, very low TSH may indicate too high a dose.

    Ideally, blood should be drawn for thyroid testing in the early morning. However, as your test is late morning, if you take your thyroxine at 6am, then the blood level of FT4 may appear to be plenty high enough. But of course there are still another 18 hours of the 24 hour period for your body to get through on that amount.

    If you don't take your dose at 6am that morning, there will be a gap of almost 30 hours by the time blood is drawn. This is not useful either.

    A couple of suggestions...

    Take only half of your usual dose at 6am, and the remainder immediately after the blood draw. Not ideal, but better than following your GP's instruction and ending up with a falsely high FT4 reading.

    Or, take half of your usual dose at bedtime the night before, and the remainder immediately after the blood draw.

  • My words 'absorption' not his. Thanks for the reply.

  • That has all been very useful. Thanks.

  • GPs do a few hours on thyroid at med school. Many people here have been researching thyroid for years. Levo peaks a few hours after you take it and then drops, so you' defintely get a false reading if you take it a few hours before blodd test as most of the time it'll be lower. TSH is highest in the early am and falls through the day, so as most GPs are obsessed with TSH, you need to show the highest level possible. Therefore, don't take levo before blood test and test first thing in the am. 11.40 am is too late for a blood test

  • I cannot change the time of bloods. So it will have to do.

  • I have been under an Andrologist and Professor before this happened; he was happy yo see me in a year's time. I am having extensive testing for other symptoms.

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