Methimazole dosage

[Sunshine998]

My dosage has been adjusted from 20 mg divided into evenly 10 mg dose twice a day to 15 mg divided into 10 mg in the morning and 5 mg at night..my question: is it better to divide the 15 mgs into three times a day or stay as prescribed?

[helvella Administrator]

Carbimazole and methimazole are very similar. Carbimazole gets converted to methimazole very quickly after ingestion.

I have written a blog which is primarily intended to illustrate why split dosing is probably a good idea, especially in the early days of anti-thyroid treatment. However, I only go as far as showing splitting into two doses rather than one.

I think the basic argument still holds, but it might not matter significantly.

Others who have personal experience might well add replies.

helvella - Splitting Carbimazole Doses

A short discussion about Carbimazole primarily focussed on splitting doses but containing other information which may be helpful to anyone taking, or considering, Carbimazole.

Last updated 10/02/2025

Link to blog:

helvella.blogspot.com/p/hel...

[pennyannie]

Hello Sunshine and welcome to the forum :

There is nothing on your Profile and we can help better knowing a bit more about your diagnosis and the lengthof time you have been taking this drug.

Methimazole is an Anti Thyroid drug and generally prescribed when there is diagnosis of Graves Disease and semi blocks your own, new dauly, thyroid hormone production.

So to follow the natural rhythm of the body it makes sense to take the same dose everyday and twice a day as prescribed -

so if with 5 mcg tablets - what about chopping a 5 mcg tablet into 2 - and take 7.50 mcg x 2 daily - AM & PM ?

Without knowing more about your thyroid journey - so Just for reference you might like copies of the most recent research I've linked in below -

pubmed.ncbi.nlm.nih.gov/338...

ncbi.nlm.nih.gov/pubmed/306...

[PurpleNails Administrator]

What would be most convenient to you & easiest to fit in with your routine & remembering medication?

Sticking to consistent timings is what’s important.

I take 15mg carbimazole in a single daily dose. I’ve taken single dose for a long time.