T4, T3 or NDT & skipping a dose for blood test? - Thyroid UK

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T4, T3 or NDT & skipping a dose for blood test?


If you're already taking a t4,t3 combo or NDT why should you skip the T4 for 24 hrs. before a blood test?

22 Replies

Not sure I understand your question, but we recommend leaving a 24 hour gap between the last dose of T4 and the blood draw, so that you get your normal circulating blood level. I don't see that taking T3 would change that. In any case, you don't exactly skip it, you just take it after the blood draw. If you take it before the blood draw, you will just be measuring the dose you just took.

For NDT, you cannot separate the T4 from the T3, obviously, so you leave a gap of 8 to 12 hours between the last dose and the blood draw, so that you don't get a false high FT3. :)

Nellups in reply to greygoose

I’m taking T4 and T3 and due a test in a week, I know about not taking the T4, and blood draw in the morning before eating or drinking, but would that be the same rule for the T3? I take my T3 half in the morning and half in the evening , so would I skip the evening and morning T3 ?

greygoose in reply to Nellups

You would take your second dose of T3 8 to 12 hours before the blood draw. So, if you were having the blood draw at 9 am, then take your evening dose between 9 pm and midnight. And take your morning dose after the blood draw. :)

GKeith in reply to Nellups

T4 is said to last 24 hours or more, T3 8-12 hours or less but, still in all, if you are taking T4 only the T3 will obviously, either be converting bad or good, high or low, in range or out, and you can "tell," so to speak where you're at as far as conversion goes. With T3, or so says I, alone in the wind, how can you tell anything as the T4, if converting to T3, its only job, is converting properly, higher or lower, if you are taking T3 pills, obviously already "converted?"

GKeith in reply to greygoose

I mean that if you are taking T3 you cannot possibly, then, see if the T4 is converting to T3 as you are, also, taking T3 and the T3, irregardless, will, obviously be higher than if you were taking just T4, as the T3 would have to be converting from the T4.

GKeith in reply to GKeith

Wait a second, I made a mistake, I see now, you could take the T4 alone if your taking them both but why? You would have to what? Take the T4 alone but how many hours apart from T4? And would that work better or worse. Too complicated. I always take 75 mcg T4 at night with 10 mcg T3 and then 2 more doses of T3 6-10 hours apart, during the day. Ah well, complications, complications, such is life and now, of course, more, much more with this corona virus . Many people are saying a large dose of vit C will help "cure" or delay or stop Covid-19 but I would be cautious. I wonder, I'm a writer so I always wonder, if T3 may actually help those who catch or before, they catch the virus. I know it is good for the heart because cardiologists prescribe them. Peace to all in these days. You know, as I wonder, these times are not unusual in history. There have been wars, killings, uprisings, etc. since time immemorial since the stone age; it's just that not until "something" actually "happens" to "you" you don't dally on it but, now, it appears as if we are all dallying on this one virus. Peace be with us all.

greygoose in reply to GKeith

Well, that's not exactly what I was saying. Lots of people take their T4 and T3 at the same time, EXCEPT the day before the test when they need to leave a 24 hour gap for T4 and only an 8 - 12 hour gap for T3. So, on that day you would have to either take them separately, or split your T3 into two doses and take one in the evening.

Too complicated. I always take 75 mcg T4 at night with 10 mcg T3 and then 2 more doses of T3 6-10 hours apart, during the day.

Agreed, it can get complicated. But, if you don't care about your FT4 level, then continue to just leave the same gap as for the T3 EXCEPT that that would give you a false high FT4 level, which might upset your doctor if he sees it.

As to vit C, T3 and the Corona Virus (good name for a band?), I think the answer to that is: no-one knows. We have these plagues - for want of a better word - about once every 100 years, and the last time round, exogenous T3 hadn't been invented. So, so we're doing the hands-on research for the next plague when it comes. As the Chinese say: May you live in interesting times. Ironic, that. :)

Smorzando in reply to greygoose

Properly LOL'd at the "good name for a band" .... Thanks GG, needed a laugh this morning 😂

greygoose in reply to Smorzando

You're welcome. :)

greygoose in reply to GKeith

Agreed. But, you don't just test FT4 to see if you're converting. You test it to see what level it is. Some people need it higher than others, so they need to know.

GKeith in reply to greygoose

Right, as usual. Thanks.

greygoose in reply to GKeith

You're welcome. :)

You don't skip them. You just time your blood test or your doses of t4 and or t3 so that your blood results are representative of what is circulating in your blood.

If you take your dose of t3 for example and had a blood test 3 hours later your Ft3 would be at a peak in your system. This would give a false picture of your general level and could result in medics keeping you on a lower dose than you need. The same goes for t4. If you get bloods done on a peak then it doesn't give a true picture of blood levels.

GKeith in reply to Lalatoot

Thanks. Peace be with you.

Usually, at least in the USA, docs are reluctant to increase their patients desiccated thyroid hormone replacement. Usually, we have to beg for a increase. Of course, obtaining BW after 24 hours since previous dose could show results that are in need of an increase. That would be beneficial to the patient. But if the dose is decent, the levels are decent, I want to see my FT3 in the middle of the day, during my usual dosing. I use NT; I split it by consuming it 6:30 AM and 3:30 PM. I go for blood work 8 hours after consuming the AM dose, before the PM dose. My levels have remained consistently optimal. I do not skip my dose, nor wait 24 hours w/o it to get blood work. If I did, the FT3 would be showing as too low for that day. The doc might then increase the dose but that would be too much for my body. Also, many docs look at only TSH. For people with no thyroid, we all know that it is futile to base thyroid hormone levels on TSH. When they see a lower TSH which is common when on desiccated or synthetic T3, they will be unlikely to increase the dose. However, for most thyroid cancer patients, keeping TSH suppressed is imperative (not for medullary patients).

What's NW stand for? or NT? Do you mean NDT for Natural Dessicated Thyroid? Do you take any T3 aside from what's in the NDT? How many grains do you take and do you believe it's better than a combo of T4 & T3? I am in Florida and have no problem getting NDT, I just have no reason to because I feel quite well on a T4 & T3 combination. Peace be with you.

helvellaAdministrator in reply to GKeith

You have, unfortunately, made a very simple mistake and replied to yourself as the originator of the thread - not Celestialbeing

NT - I suspect Nature-Throid

NW - I can't see it anywhere?

GKeith in reply to helvella

Sorry, thanks for the tip.

Hi, I just saw this. NT is NatureThroid. BW is blood work. I only take DTE-desiccated thyroid extract NatureThroid brand. For me, it is better than a synthetic compound/T4/T3 combination. I tried that. Synthetic T3 did not work and gave me side effects. Glad you are ok with yours!

I've always been tempted to take some NDT but never have because I feel good on a T4, T3 combo, at the present time, but if that ever changes, I will try it. How many grains do you take? So, is calcitonin calcium? I've actually heard that NDT's are changing as the generic brands have too many added sugars and fillers and have been changed now far too many times by Big Pharma. Peace be with us all in these times.

My grains amount is odd. I use 1.625 grains of which I obtain with an extra 1/8 grain from a lesser amount. I have to order two different size pills. Weight-wise, I use a 97.5 that I split AM and mid-afternoon and a 1/4 of a 32.5 in the AM.

Whatever works, for you personally, is the right dose. Doctors must learn to treat the patient and not (just) the symptoms. Peace be upon us all in these times.

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