Log in
Thyroid UK
91,982 members106,233 posts


Hey people! So i had been taking Mexican Cynomel for 3 years at 50mcg split per day. I had felt okay ,and my tsh was stable at 0.5. But as most of you know, this product is no longer in circulation.

I've recently, for the past 6 weeks been taking the same dose, but mercury version, and i feel more tired, and my TSH has risen to 38!!!

Is there anyone who has been in a similar position? And if so, have they found increasing the amount of NHS version has been successful?

I would very much appreciate it if someone can PM me with regards to sourcing a better make of this product from overseas.

Thank you :)

5 Replies

Buggles, how much Liothyronine are you taking?


As above Clutter........50mcg.


Buggles, sorry missed it. Some members have said they find Cynomel more potent than Liothyronine and Tiromel but I can't believe it would cause the fluctuation in TSH you've had.

There are several possibilities:

1. Lab error. If they hold the sample they could retest. Or retest using a different lab.

2. Heterophile antibodies to TSH interfering with the assay. Different analysis method can be used to remove the antibodies.

3. Dodgy batch of Liothyronine. Ask your GP for another prescription and make sure you get a different batch no. from your pharmacist. If it is a dodgy batch, please make a yellow card report yellowcard.mhra.gov.uk/ In the meantime I would increase your current batch to 70mcg.

4. Reduced sensitivity to thyroid hormone. If TSH is still high after next blood test GP should consider this and refer you to endocrinology.

1 like

It could well be another dodgy batch as that's happened a few times with Mercury.

Post your Batch No. on a new question for responses if anyone is on the same.

I had the same problem last year as did others and at first you don't realise it is the T3. Others also reported it to the MHRA which you should do if you are having symptoms. Your TSH has gone far too high.

1 like

Thanks. I would like to know what are people taking now that cynomel is gone?

my batch is 83200.


You may also like...