These suggestions are gleaned from years of members experience to best achieve an average reading of thyroid hormone levels with highest TSH. They are calculated considering assimilation and half life's.
TSH and thyroid hormones have an inverse correlation but signalling commonly becomes skewed meaning results are distorted. Some members may suffer low thyroid hormone levels whilst TSH remains within range, or adequate thyroid hormone levels with TSH below range. This is something not readily recognised by the medical profession as yet and for members dosed solely by the TSH, it is important to follow the suggested testing protocol to reduce risk of dose reduction and increase chance of a dose raise if appropriate.
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Synthetic meds - These are considered body-identical but are ‘free’ hormones (not bound to a protein) so work much faster.
Levothyroxine (T4)
To achieve highest TSH, have blood drawn early morning whilst fasting (water only). Leave 24 hours between last dose and blood draw.
Bedtime Levo medicaters can achieve this by the old suggested method of taking half Levo dose 12 - 14 hours before the blood draw and then 1.5 dose following the blood draw.
Alternatively Jaydee1507 suggests 36 hours or 2 nights before test, skip night time dose and take the following morning. Day of test, take immediately after blood draw. Bed time day of test take Levo as usual.
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Combo of Levothyroxine (T4) + Liothyronine (T3)
T3 commonly distorts the TSH gap further and even a small amount can have a profound effect, but considering the T4 the suggestions remain the same to have blood drawn early morning whilst fasting (water only) to encourage highest TSH.
T3 has a shorter half life and many split dose to reduce chance of early onset and prolong its action. The last dose should be taken between 8 - 12 hours before the blood draw. Those who don't split dose are recommended to do so the day before the blood draw.
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Liothyronine (T3)
Not many are prescribed T3-only, but are self medicating or under the care of a specialist who recognises the effects of T3 on TSH. Therefore, forum suggestions become less relevant.
Gleaned from posts by the forums resident scientist diogenes.
Testing thyroid hormone levels when medicating NDT can be viewed differently. The intact thyroid produces T4 and T3 tightly bound to a protein called thyroglobulin, only degraded by a gland-linked enzyme that releases the hormones.
When we swallow NDT, the enzyme specific is missing and our hormones remain bound to thyroglobulin until reaching the stomach and small intestine where digestion eventually releases the hormones. There is also possible further delay in release because the stomach enzymes are not identical to that of the thyroid gland, and it is thought these two factors form a kind of natural time-release. This delay is most likely accountable for the smoother ride many feel when medicating NDT, and means although it contains T3, testing may be the same as for T4-alone to still achieve an average reading.
Leave 24 hours between last dose and blood draw. There is no need to split dose the day before unless this is your usual dosing method. Many on NDT are self-medicating or under the care of endo’s in the know regarding alterations in TSH, but if necessary highest TSH levels may be achieved by having blood drawn early morning whilst fasting.
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How we chose to test is individual but the most important thing for ongoing monitoring is to always test like-for-like.
If anyone has anything else to substantiate the above for members reassurance, please respond. tattybogle usually has good graphs showing TSH highest in the morning or after fasting 😊.
helvella SlowDragon can this be pinned please?
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TAKING LEVOTHYROXINE 24rhs BEFORE BLOOD TESTS. and 9am TESTING:
In case you , (or your GP) don't understand why we recommend to delay taking the morning dose of Levo until after a blood test at 9 am :
~ This paper confirms why it is 'best practice' for GP's to test thyroid blood tests (TSH and fT4) at a CONSISTENT TIME OF DAY and BEFORE taking that days Levothyroxine dose :
Biological variations are expected to occur in the [FT4] and [TSH]. A very important condition for TFT measurements is the time of day the blood is sampled as many hormone systems in the body exhibit natural circadian biorhythms dependent on time including the HPT axis. The diurnal rhythm of [TSH] plays an important role and exhibits a significant difference between morning and evening readings [8]. The reported variations in [TSH] levels are ranging from an average [TSH] of 1 mU/L at about 15.00 h in the afternoon to an average of [TSH] = 2 mU/L at about midnight. This reveals the importance of a repeatable defined measurement regime at a fixed time of day. Any measurement accuracy of [TSH] to the extent we have available loses significance if we ignore these effects.
The amount of variability is dependent on the individual in question, but the smallest interindividual variations in [TSH] are observed around 15.00 h in the afternoon [8].
In another study [9], it was evident that several persons being probed for FT4 after taking their daily dose of levothyroxine (L-T4) had different readings because of interindividual differences in pharmacokinetics and metabolism. Therefore it is important to probe a person already using L-T4 on a fixed time of the day before the intake of the daily L-T4 dose. For practical reasons, this can be done shortly upon awakening (i.e., prior to the ingestion of daily dose of L-T4) in the early morning between 07.00 h and 10.00 h. The same time interval for TFT assessment also applies to people being investigated for the first time."
This shows how our fT4 level peaks between aprox 2-6 hrs after dose , then gradually falls , by aprox 12hrs post dose, the fT4 level is more stable and fairly close to it's settled level, but for the most consistent/ comparable results ,testing aprox 24hrs after the last dose is usually recommended :
(Published: 01 April 2022 in BMC Endocrine Disorders)
"Discussion
The findings of this study showed that the TSH level was reduced significantly by about 30% after calorie intake in the morning, The components of calories had no significant influence on TSH variation rate when the calories intake was similar. The TSH level was reduced slightly by 5.2% in the subjects after maintaining the fasting state. The rate of TSH reduction was significantly pronounced after calorie intake compare to the fasting state, suggesting that the influence of food on TSH was more evident than the diurnal rhythm of TSH.
The findings of this study showed that the variation of TSH level after calorie intake in the morning might influence the diagnosis of subclinical thyroid dysfunction. Subjects with subclinical hypothyroidism might be underestimated due to the non-fasting state.
Conclusion
In summary, the TSH level was reduced significantly after food intake, compared with that at fasting state in the morning. If the reference range of TSH used in the laboratory was from fasting blood samples, it would be better to evaluate the TSH level in fasting blood obtained in the morning compared with random or postprandial samples."
** new study with better graph ** ncbi.nlm.nih.gov/pmc/articl...Increased fT4 concentrations in patients using levothyroxine without complete suppression of TSH (Heleen I Jansen, Marijn M Bult, Peter H Bisschop, Anita Boelen, Annemieke C Heijboer,Jacquelien J Hillebrand 2023 )
"Timing of blood withdrawal following L-T4 intake can lead to high fT4 concentrations without (complete) TSH suppression. Hypothyroid patients are mainly treated with L-T4 and the effect of treatment is monitored by measuring serum TSH, sometimes accompanied by fT4. Hypothyroid patients are advised to take a single daily dose of L-T4 orally in a fasting state. L-T4 administration in the morning or at bedtime is considered equally effective as long as L-T4 is taken on an empty stomach to ensure optimal uptake (14, 15). In contrast to fT4, no direct alterations of TSH and T3 have been reported directly after L-T4 ingestion (4, 5, 6, 7, 8). An fT4 course as Fig. 2 presents was found in patients taking L-T4 in the morning before breakfast, and one would also expect an increase in fT4 levels during the night when L-T4 is taken at bedtime (16). However, literature on extensive follow-up of fT4 and TSH levels following L-T4 intake in the morning compared to bedtime is lacking. Ain et al. (7) as well as Hoermann et al. (17) specifically emphasized that fT4 concentrations in L-T4 users were influenced by the time of day, meaning the time interval between L-T4 intake and blood sampling should be considered in the interpretation of fT4 values. In line with this advice, the European Thyroid Association guideline on treating central hypothyroidism advises blood withdrawal for monitoring treatment to be performed before L-T4 intake or at least 4 h after L-T4 intake (18), but other international guidelines do not yet (19) ......Physicians and laboratory specialists should be aware of the importance of timing of blood withdrawal and the timing of L-T4 intake to avoid questioning the assay’s performance or, worse, unnecessarily adapting L-T4 dose in patients. "
Studies on TSH and fasting generally show no difference although they have been of poor quality. The more recent study mentioned by tattybogle appears to be well conducted and shows a remarkable effect with outstanding p-values (<0.001). Although the researchers are well qualified there are serious concerns about science coming from China nature.com/articles/d41586-... . Most other studies just about manage to achieve statistical significance. Fig. 1 bmcendocrdisord.biomedcentr... from the study shows exceptionally clear distinction between the fasting and non-fasting groups, something other researchers have never been able to achieve. This study needs to be replicated by another team.
IF for the moment we assume the morning meal lowers TSH then provided you have the blood taken before breakfast overnight fasting shouldn't be necessary. The study participants fasted overnight but the study does not claim that overnight fasting affects early morning TSH. As far as I know this has never been claimed by anyone.
I appreciate many patients want a higher TSH in order to achieve a diagnosis or not have their hormone dose reduced. Sadly, this is playing the game and leads to worse treatment for the majority over time.
I have noticed that a large number of patients on the forum who have the worst symptoms tend to have low normal fT3, fT4 and TSH. The problem is the low TSH; making TSH look 'good' reinforces doctors' belief in the infallibility of the TSH test. it is the low TSH that is the problem and a normal TSH with low normal fT3, fT4 indicates TSH with low bioactivity.
In summary, there is no trustworthy evidence that overnight fasting affects TSH. TSH is higher early morning, increases during the morning and levels off around midday. You will get a higher TSH from an early morning blood draw but bear in mind TSH is varying rapidly at this time of day and so it will be more difficult to compare results. In any event we should try to stop doctors over-interpreting an isolated TSH result. How TSH reflects fT3 and fT4 is far more important.
Edited. I didn't realise the Nature article is behind a paywall (I have a copy). Here is an FT commentary ft.com/content/32440f74-780... .
I don’t agree with everything he says I hasten to add.
I can’t read the article on the reason why Chinese research is suspect, I’d guess it’s very tightly controlled by the government, corruption in another guise?
The Nature article about Chinese paper mills churning out fake research is simply behind a paywall, that's the business model of Nature. There are lots of concerns about medical research, particularly thyoidology where much research is sloppy or biased as in the repeating of studies that fail to show benefit for T3 therapy, repeat the studies and then claim x studies show it doesn't work. No attempt to find out why the studies failed.
I mustn't drift off topic, I raised the issue about the Chinese study on fasting because their results were so exceptional but the study team includes people with track records so it's difficult to know what is what. The study results need to be confirmed by another team, this is how other sciences work.
I’ve tested at all times consistently (if that makes sense 😬).
When first on T3, I always tested 2 hours post dose to achieve highest peak for endo. My physical improvement was so utterly miraculous after introducing T3 endo made me a case study. In reality all this involved was having extra labs/tests at my GP’s and agreeing to adhere to strict testing protocols which I did.
I used to test NDT 12 hours post last dose. Now always 24 hours and no split dosing.
Wish I could test 24 hours later but it's not possible. I have to split my doses to keep my heart happy and the longest I can wait between testing is about 14-15 hours.
PS....I love that you were a case study. Hopefully it paves the way for others
p.s helvella do you have a reference to where where that graph is sourced from .. i have used the same graph in a reply above , but am aware i haven't given a ref for it's source ,,and now have no idea where i found it .
I thought your graph was from Bianco's 2020 'Evidence Based Use of LT4/LT3 Combinations in Treating Hypothyroidism: A Consensus Document' but it appears it was actually reprinted with permission from Saravanan et al's 2007 'Twenty-four Hour Hormone Profiles of TSH, Free T3 and Free T4 in Hypothyroid Patients on Combined T3/T4 Therapy' which is behind a paywall.
radd members often ask about how to switch their usual bed time levo dosing to morning temporarily to achieve the 24hr gap spacing requirement to show stable blood levels.
I believe the procedure is as follows.
36 hours or 2 nights before test, skip night time dose and take it the following morning.
Day of test, take immediately after blood draw.
Bed time day of test take Levo as usual.
I'm sure someone will correct this if it is wrong. 😅
i do it that way .. if i started messing around for 2 days before hand i'd get in a mess.
if i'm regularly splitting levo dose anyway (half am/ half bedtime) , then i just bring the bedtime dose forward a few hours to eg 8/9 pm . so that there is at least 12 hrs before test ~ 12hrs is long enough to miss the peak and allow fT4 to get back to "more or less" base level.. even if the full dose is taken .... it will be a little lower at 24 hrs but not very much.
Stretching doses out and taking the missing dose after the test (the method often quoted by admins for moving evening to morning dose before tests) means you have one full dose "less" on board at the time of the test ... so that method provides a slight underestimate of regular T4 level.
Whereas testing 12 hrs after last dose , (or last half a dose) will provide a slight overestimate of regular fT4 level.
So neither method is perfect for bedtime levo takers
I prefer to use the much simpler 'slight over estimate' method with much less chance of getting in a mess with my doses.,, also much easier to remember how i did it next year for consistency.
After 12 hrs fT4 level will only be very slightly higher than it would be at 24 hrs anyway ..so for me it's not worth the hassle of moving everything around for days before hand .
Fasting and 24 hours but couldn't elaborate when T3 was taken as the question moved on.
He also said TSH had no function in the body when the gland was completely gone (apart from thyroid hormone of course). This turns the TSH receptors in bones upside down 🤷♀️.
I need to re listen as was outside sunbathing 🏖☀️, couldn't locate my headphones and seagulls kept interrupting 🤣
For those on combi, test first thing, fasting, before taking medicine, then again three hours later having taken medicine.
That should show trough and peak. He wants to keep T3 within reference interval at all times.
I'm not 100% convinced. After all, any T3 taking is different to the slow and pulsatile release of T3 by a healthy thyroid. And the peak is so brief, not convinced you can be sure of catching it. Also, the issues of various split-dosing regimes.
Yes, I heard that bit. That's the protocol I received from my endo except he used 2 hours post meds. It's useful if you want T3 to stay within the ranges as I always have.
Vit D procurement abruptly halted by todays showers ☔️.
I am prescribed liothyronine (T3) alone and am free of symptoms and feel well. I take one daily dose of T3 when I awake with one glass of water and wait an hour before I eat.
Also my new GP seems to be very knowledgeable whereas other doctors in the surgery have made some statements to me and I've told them they are wrong.
Shaws it's about time you found a Dr that knows what he is talking about. Your Dr is a Keeper . I very excited for you. Lets hope that other thyroid patients find their Dr that knows and treats the way we ought to be treated.
Thank you jgelliss, I have also had some really stupid responses from a couple of GPs and I've told them they're wrong .
I am not 'Miss Knowall " by any means ' but, in theory, I shouldn't know more than 'supposed to be' GPs who cannot diagnose/treat patients who're hypo which should be easiser once you are aware of clinical symptoms. Initially one told me I had no problems and blood test was o.k. even though TSH was 100.
I hope you find that you are improving and relieving all clinical symptoms
Are we supposed to reach for highest TSH so our practitioners keep scripting us T3? That's why I do it. I also will do things like eat seaweed for the morning of the test. That's how my TSH was 0.8 despite my FT3 being upper quartile.
Don;t understanf the logic there kimbriel , can you explain ?
Do you mean eating seaweed on the morning of the test in an attempt to raise TSH result ?
I think this is unlikely to have any instant effect on TSH result , mainly because a large amount of that days TSH volume has already been produced overnight.
but i'm still struggling to see how it could make TSH go up ON THE SAME MORNING as eating some ... impossible to prove of course unless you've tested TSH immediately before eating iodine and then tested again a short while afterwards (how many hours are you eating it before the test ?) .. you'd have to take into account that TSH falls over the hours of the morning anyway eg it would be a bit lower at 11 am than at 9 am anyway even if you do nothing.
I always test between 8 or 9am. If you think that it would be better to ingest iodine the night before, try that. I just know that I tested TSH mere weeks before without iodine and it was 0.4, then I added iodine and it was 0.8.
I was interested in what Dr Bianco had to say about the testing for those on combination of T4 and T3 but it did not seem practical with the current state of the NHS. He seemed to assume that patients did not split their T3 dose and usually took meds together in the morning. He suggested testing on an empty stomach, then dosing, and then testing again 3 (or was it 5?) hours later so you get a trough and a peak reading. He also stated that the correct dose of T3 should be calculated by weight of patient, like levothyroxine, but he did not give the calculation. He also seemed to say that he did not like a suppressed TSH and patients on combination therapy should reduce their T4 until the TSH is in range. I wondered whether you saw his presentation and what you think about this as it is a different approach?
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