Thyroid UK
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Block and Replace VS. Titration?

Hi guys, I'm new on here and would love to get your opinion on something.

I'm 38 and have recently been diagnosed with Hashimoto's and Graves. My T4 is currently 19.3 (highest was 22.6) and my TSH is less that 0.02.

As I would like to start a family (I'm nearly 39) my consultant has suggested carbimozole and thyroxine BLOCK & REPLACE as this would be a 1 yr programme (as apposed TJ titration which is ideally 18 months).

I kind of had my heart set on titration (b4 I knew the timescales) as I thought this would give a better indication as to whether it was working (ie. if levels improved).

Is this true?

From what I've read, block and replace would only indicate its success once the course of treatment was complete and I came off the drugs.

I'd love to hear your thoughts / experience on titration vs. block and replace, how they tend to play out, and when one would be used rather than the other.

Many thanks

Emma x

9 Replies


Do you have the FT4 lab ref range (the figures in brackets after the result)?


Yes it looks like the:

TSH is <0.02 (0.27-4.20) mU/L

T4 is 19.1 (12-22) pmol/L


Hi Emma, so you're not hyperthyroid as 19 is still well within range. Do you have trouble with your other hormones? I guess I'm a bit confused as to why you have to treat at all. With graves a suppressed tsh is common but not dangerous. If you didn't have graves a low tsh would be a sign of sub clinical hyperthyroidism but unless you are experiencing symptoms then having a ft4 of 19 is quite a good thing. You may not need to treat at all. Block and replace is useful but all those meds would definitely interfere with your pregnancy plans and a year is only a starting point. In Japan where b&r is most common some stay on for up to 4 years


Hi, thanks so much for your response. My TSH Receptor Antibodies is 4.1 which apparently indicates a very low reading of Graves (according to consultant). I have symptoms of feeling "on edge", heart palpitations, struggling to concentrate, feeling very anxious and my T4 was only 13 in September 2016 which my consultant thinks is probably my normal... Does this help?


It's really interesting, I've also heard this idea from a consultant that different people have different optimum thyroid levels. T4 of 13 would seem very low, almost hypo to me but then you have all these symptoms that are troubling you. I agree with Clutter that it would be important to ask for ft3, since that KS the active form of the hormone and also look at your supplements. There are prenatal supplements with high iodine etc which could be contributing or else you may also be low on magnesium based on your symptoms. Idk exactly but I'd discuss both those things with your doctor n I guess explore all your options before drugs. Otherwise carbimazole alone gives your body less drugs but I don't think any method has a guaranteed timeline



I agree with Cat4Health. I don't think you need Carbimazole just because TSH is suppressed because FT4 19 is well within range. Has endo not checked FT3?

If your FT4 rose over range then anti-thyroid drugs would be appropriate. Because Carbimazole can cross the placenta and potentially cause hypothyroidism in the foetus pregnant and breast feeding women are usually switched to Propylthiouracil (PTU) to control thyroid levels.

My TSH has been <0.01 for 5 years but my FT4 and FT3 are both within range so I am not over medicated on T4+T3.


Hi there, thank you so much for your response, this is so interesting and I'm so glad you've shared this with me. I don't think Endo has taken FT3 levels (not on blood tests). My T4 has dropped to 19.3 but I don't feel right (feel "on edge", wired (like I've had 10 cups of coffee) so it's hard to focus and concentrate but fascinating that your TSH has been <0.01 for 5 years. Do you mind me asking what your T4 level is and your symptoms?

Many thanks, Emma



It isn't relevant because I have no thyroid and am taking Levothyroxine and T3 but FT4 is 14.9 and FT3 6.15. I felt dreadful when I was over medicated a few years ago and FT4 was 35 but now I am optimally medicated I have no symptoms.

If I were you I would order a private thyroid test including FT3 via and I would decline B&R or Carbimazole unless FT3 is over range.


Hi Clutter, I just wanted to say a big thank you. I went and seeked a 2nd opinion and amazingly they disagreed with the carbimizole suggestion from first endocrinologist. She ordered more bloods including T3 and said that whilst my T4 was in normal range she would recommend I continue with the Beta-blockers and see if T4 naturally comes down. I am also seeing a homeopath and might look in to a nutritionist / naturopath. I have also been gluten free for 2 months (although can't overly say I feel any better). Any way just wanted to say thank you, your comments made me really think and convince me to get a 2nd opinion, Emma :-)


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