Time of blood test

[Jadedflower1944]

I asked the dr yesterday if not taking thyroxine and not eating would make any difference to blood tests results. She was adamant that it doesn't .

[Hidden]

Thanks for asking that question jadedflower. I've left a message with my endocrinologist's secretary to ask that question before I have my blood test next week! I know from this forum that I should NOT take my liothyronine before the test. 'M'

[Clutter in reply to Hidden]

Mabsie, see my reply to Jadedflower below.

[Hidden in reply to Clutter]

Thank you Clutter 'M,

[SeasideSusie Remembering]

Well that's no surprise. She might also be one of those who thinks a rising TSH at the very top of the range and a very low FT4 doesn't indicate hypothyroidism either. A lot of doctors know diddly squat about thyroid.

I'm sure someone has posted recently about their enlightened endo mentioned about leaving meds off for 24 hours. A quick search and I haven't found the post, perhaps someone else remembers it.

[Jadedflower1944 in reply to SeasideSusie]

I have read on many forums not to take thyroxine before test .Just don't know what is best

[SlowDragon Administrator in reply to SeasideSusie]

Yep - that was me.

My endo was very clear....said definitely don't take Levo in the 24 hours before a blood test. Otherwise the test just reflects the medication you are on, not the way your system is really coping and true levels you are at.

[strawberrysorbet in reply to SlowDragon]

My endo said the same thing, so some of them know what they are talking about.

[humanbean]

In order to get diagnosed with an underactive thyroid we need to show we have a high TSH level.

For the source of the information on timing of the test, see this paper :

press.endocrine.org/doi/pdf...

Look at the graphs on page 2.

As you can see, TSH is highest in the middle of the night. Since getting blood tests in the middle of the night doesn't happen under normal circumstances, we all have to do the next best thing and test as early in the morning as possible.

If you look at the graphs on page 3 you can see that the amount of thyroid hormone and TSH variability in people varies quite dramatically. If you happen to be one of the people whose levels vary strongly then having your blood tested at the right time could make the difference between being told your thyroid is fine and being diagnosed with a thyroid problem.

[shaws Administrator]

You may come to realise that a doctor and some endocrinologists aren't the best people to get answers from with regard to a failing thyroid gland. Unless our bloods are well out of range we don't fair well.

As the saying goes, education, education, education, is the best way forward but it is us who have to educate ourselves about how to recover and go forward by sourcing thyroid hormones which suit us. Unfortunately, we may be prevented even if taking levothyroxine by being denied an optimum dose to keep our TSH 'in range, even if that is towards the top when the majority of us feel improved around 1 or lower.

Many medical professionals are unaware of this simple phenomenon.

[Jadedflower1944]

So obviously it does no harm to miss the dose or take it later. Does it also mean no food either ,even just a piece of fruit

[humanbean in reply to Jadedflower1944]

Lots of people don't feel well on levothyroxine. Doctors sometimes blame the patient for not taking it regularly (and sometimes they are justified). In those cases the doctor may tell the patient they have to be observed taking their meds. So arrangements are made for the patient to go to the surgery once a week and take enough levo for an entire week while someone watches.

Someone who doesn't remember to take their thyroxine often enough will show different patterns of thyroid function test results compared to someone who takes it regularly. If they have suddenly remembered to take a few days worth of levo just before a test, having not taken it for a month, then the doctor may well be able to tell from the blood tests - both TSH and Free T4 would be high.

Timing for levo doses isn't critical, there are lots of ways of fitting it into your life. But it must be taken, not forgotten, and it is critical to take it when the stomach is empty, and supplements and food must be taken sufficiently far away from when levo is taken.

I think the rules are : Take levo one hour before or two hours after food and supplements. There are exceptions though - iron, calcium, vitamin D and oestrogen must be taken four hours away from taking thyroid meds.

[greygoose in reply to humanbean]

Add magnesium to that list. Although, to be honest, it's best to leave six hours between magnesium and thyroid meds!

Oh, and Jadeflower, not even a piece of fruit!

[humanbean in reply to greygoose]

I didn't know that about magnesium! I never stop learning.

[greygoose in reply to humanbean]

I only found out recently. I'd been leaving two hours! I thought I needed a increase in my dose, but maybe just taking the magnesium earlier will work. We'll see.

But that also applies to indigestion medicines that have magnesium in them. So, that's something to think about, too.

[Jadedflower1944]

I didnt know ppl take a weeks dose at once. Wow. I have never forgotten to take mine .whenever I get up in the night for the toilet I take it. Could be 2 am 3am etc but never forget

[Angel_of_the_North]

Well, perhaps she hasn't read the studies - GP's and endos are very busy.

[Clutter]

Jadedflower, she's wrong. TSH is highest early in the morning and drops post-prandially.

healthunlocked.com/thyroidu...

ncbi.nlm.nih.gov/pmc/articl...