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NDT time to work

I need to know, how much time does it take to NDT to work? is it six weeks like T4 medications or it works differently?

Thanks,
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Since NDT med is over 80% T4,  it would be best to wait at least 5 weeks before another blood test.  That way  the T4 should have reached over 95% of its full effect on serum levels.  
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Avatar universal
I meant time to blood test !
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1756321 tn?1547095325
NDT didn't work for me at all as I was not absorbing it. Increased to 3 grains daily. Nothing but my hypo symptoms worsening. Switched back to synthetic T4 very quickly.

Excerpts from the book: Thyroid Diseases: Clinical Fundamentals and Therapy by Fabrizio Monaco, Maria A. Satta, Brahm Shapiro, Luigi Troncone...

"There is some differences in the rate of absorption between animal and synthetic preparations. After a single oral dose of synthetic L-T4, the absorption is approximately 70 - 80%, 20 - 30% being recovered in the stool.  It is absorbed rapidly, mainly in the distal small bowel, reaching maximum plasma levels in 2 to 4 hours."

"Variability of absorption also occurs with desiccated thyroid, dependent on proteolytic enzymes of the gastrointestinal tract. Since desiccated thyroid and thyroglobulin preparations contains T4 and T3 incorporated into thyroglobulin, to release thyroid hormone the crude preparations must be hydrolyzed by gastrointestinal proteolytic enzymes, which indirectly influence the absorption of T4 and T3."
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Avatar universal
"Working" can mean different things.  NDT contains both T4 and T3.  T4 has a half life of about one week, meaning that serum levels will show half of the amount of the dosage in the first week.  So it takes about 5 weeks for most of the T4 to be reflected in your blood.   T3 has a half life of slightly less than a day, so a T3 dose will be be fully reflected in serum in less than a week.    However,  when you start on thyroid med, your TSH will go down and the output of natural thyroid hormone from the gland will drop.    Since serum thyroid levels are the sum of both natural thyroid and thyroid med, the  net effect on Free T4 levels will be essentially unchanged until your TSH is low enough that it no longer is stimulating the thyroid gland very much.   After that, additional increases n med dosage will start to raise Free T4 levels.   Free T3 levels on the other hand may go up slightly and people sometimes notice a short term effect, dependent on the dosage.   Make sure you always get tested for both Free T4 and Free T3 (not Total T4 and Total T3) every time you go in for tests.  

If by "working" you mean symptom relief, that is a different matter.    Many of us have found that hypo symptom relief required our med dosage of NDT to be high enough to  get Free T4  near mid-range, and Free T3 in the upper part of its range, and adjusted from there as needed.  Also be aware that symptoms don't magically disappear when reaching optimal levels.  It sometimes takes some time for the body to heal and symptoms to go away.  

Reaching adequate levels will usually also suppress TSH below range, which causes most doctors to decide that you are thus hyperthyroid and need a dose reduction.   This is very wrong., unless there are attendant hyper symptoms due to excessive levels of Free T4 and Free T3.     There is scientific evidence that the TSH is suppressed for almost a full day after a significant dose of thyroid med, so that does not usually indicate an overdose.   You can tell by Free T4 and Free T3 levels.  

Hypo patients are also frequently deficient in Vitamin D, B12 and ferritin, so you should make sure to always get those tested and supplement as needed to optimize.  D should be at least 50 ng/mL, B12 in the upper part of its range, and ferritin should be at least 100.   Very important for a hypo patient.  
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