Thyroid UK
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Optimal bloods if on NDT/T3 combo

Hi all,

I understand if you are NDT only - you should be shooting for removal of symptoms and FT3 is at the top of the range, and FT4 midrange

However, my husband has added some FT3 (10mcg) to a lowered dose of Armour. What are the optimal blood tests on this regimen? Do you still look at the FT4 measurement?

Reason for lowering the dosage of the Armour was hyper symptoms above 2.25 grains (very fast heartrate and anxiety) but hypo symptoms on any dosage lower than this.

If he is having both hypo (fatigue) and hyper symptoms (high heart rate once or twice a day and some anxiety but not as bad as on the 2.25 Armour) at different times of the day on this regimen then what would you change? The armour dosage or the T3 dosage?

Iron and cortisol are ok.

Be interested if anyone else has been through this and found their "sweet spot"!

4 Replies

Icoc, TSH is often low/suppressed and FT4 low because of the T3 in NDT. Taking oral T3 can mean there is less need for high T4 storage as the need for conversion is bypassed. More important is FT3 level. Generally being in the top 3rd to top 75% of range is good. Top of the range may be too high for some people and cause hyper symptoms.

It's usual for heart rate and pulse to increase within an hour or two of taking NDT or T3 as the T3 peaks in the blood. Usually they subside within an hour.

Has your husband had vitamin D, B12 and folate checked? They're often low/deficient in hypothyroid patients and this can cause musculoskeletal pain, fatigue and low mood.

The link below discusses feeling hypo and hyper at the same time:


Is his ferritin now more than 80 then? Reading back through your posts I saw a 40 three months ago. The most common causes of jitteriness when trying to raise dosage are low ferritin or weakened adrenal glands. You say his cortisol is fine - did you establish that via a saliva test?

Apologies if I'm asking about stuff you definitely know to be fine - as you know, we get so many doctors tell folk here that their blood results are fine when they really really aren't!


Regardless of your type of medication, most people feel best when both FT3 and FT4 are in the upper half of the reference range. Some people cannot attain this on 100% NDT, because NDT has a higher T3/T4 ratio than found in humans. The way to get closer to a human ratio is to simply add T4 to NDT. Here's a VERY conservative formula to get to a ballpark dose. You fine tune your dose from there, usually upwards.

Fatigue is also a hyper symptom, and he may be on too much T3:


Thanks all yes his vit d, etc have all been checked and are fine. From what you are saying we have 3 possible choices:

1)will increase the t3 by 5 mcg.

2)If this doesnt work we might try a lowered t3 and slightly increased ndt 3) addition of levo.

The hyper symptoms seem to be subsiding and hypo coming back to the fore. Thanks for the advice


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