Thyroid UK
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NDT dosing and side effects

Hello all

So I made the switch to NDT just this past week. My doc prescribed Erfa thyroid one 30 mg tab twice a day (so total 60 mg). so I take one at 7:00 am and the other at 2:00 pm. This is now day 4 and I am more achey, more emotional, gut upset, and generally tired (tho not as exhausted in late afternoon and into the evening).

Prior to starting the erfa NDT, I was taking .125 synthroid and 5mcg slow release cytomel each morning and 1/2 capsule of over the counter 65mg thyroid at 1:00 in the afternoon. Initially felt better with the addition of the 1/2 capsule but, after three weeks or so, had noticed higher fatigue and constipation returning.

My labs done just prior to starting the Erfa NDT were:

TSH : .03

Free T4: 23.5 (range 10 to 25)

FreeT3: 3.8. (Range 3.6 to 6.8)

TPO: 113. (Up from 85 at previous measurement before over the counter NDT)

So my doc is telling me the NDT dose I am on contains less T4 and more T3 so she is hoping to see the T4 go down (goal is around 18) and the T3 to go up (goal is around 5).

In the meantime I am not feeling great. I tend to be very sensitive to changes in dose of almost anything.

Is it usual for people to have difficulty with this transition? Does the dosage and the rationale for the dose i am now on make sense?

Any suggestions or thoughts would be much appreciated!!

7 Replies

Wayt2Tired, you feel rubbish because you are undermedicated. 60mg Erfa is bioequivalent to 75mcg T4 which is almost half the 125mcg and 5mcg T3combined dose you were previously taking. I think 2 grains would have been an appropriate starting dose.

Your doctor didn't need to target FT4 18 when you were on Synthroid. FT4 needs to be high on Levothyroxine for T4 to T3 conversion and yours was still within range.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Hi waytootired, Clutter's calculations are correct. You have reduced your total dose and you are now getting 9 mcgs of T3 (per one grain of Erfa). It didn't appear you were converting your FT4 very well since it was still high in spite of the fact you were taking straight T3. Not sure what your half capsule means. Is that T3 or NDT? I think you should continue the cytomel though it's not clear what exactly you were taking but you have to give it more than a week for your body to adjust to the new paradigm.


Thanks for both replies. I am really surprised as I talked to the pharmacy today and he said that 60 mg of Erfa was equal to 100 mcg of synthroid and 9mcg of T3! No wonder I am feeling so wonky!!

The 1/2 capsule was an over the counter 65 mg thyroid (bovine) my naturopath prescribed. My understanding was that it was much weaker than the prescription stuff but still would have added some T4 and T3 to the morning dose.

This is so frustrating, confusing, and rather frightening when you are putting your trust in professionals who don't seem to know what they are doing.

I am really not sure what to do and am a bit nervous about doubling the dose as I went hyper on 10 mcg cytomel in October.


Way2tired, it's a bit confusing what you are taking. NDT like Erfa is usually measured in grains rather than grams. This is an old fashioned term. I think 1 grain is equivalent to about 65mg. This will contain 38mcg of T4 (equiv to synthroid ) and 9mcg of T3 (equiv to cytomel). I take a different brand, but mine says on the bottle how much of each it contains.

Perhaps the over the counter you had may have been nutri-thyroid? This is a package of things that support thyroid, but isn't supposed to contain any T3 or T4.

So you probably feel worse because you're on a much lower dose. For comparison, T3 is often said to be about 4x as strong as T4. Although it depends on your metabolism. This is not a disaster, Though, because the way people generally start on NDT is to increAse it on a weekly basis until they feel better. So you would normally increase quite soon.


Dr. Lowe was a real expert on hypothyroidism and produced a bovine source but had to take many capsules to be equivalent to the porcine source of thyroid hormone which is closer to human. I don't think it is of much use because of that but haven't seen any current research.

While T3 is more potent, it's half life is under one day. T4 has a half life of a week or two so they should be regulated with that in mind. It may be the T4 that is giving you problems. You still have Synthroid in your system probably for weeks.


Thanks so much for the info and the support. I see my naturopath on Thursday so will have a conversation about dosing. Sounds like I may need an increase in NDT but also that I just need to be patient and give it a few weeks to see how it all settles out. Hard to be patient when I just want to feel like I have some life in me again. sigh.....

Thank you for the quick responses! Really helps to feel there are others who "get it"!


You can be sick. I was on NDT and thyro gold for 2 months. I felt sick like you but less pain than levo though. My body was hot, emotional, tremor...upper right belly. It also developed my uterine myoma again. I sweat too much more than when I took levo.

NDT seem to increase estrogen which also increase cortisol. Estrogen makes you emotional due to lack of Tryptophan and B6. Also your liver is hard to detoxify it.


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