Thyroid UK
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Has anyone else had a low white blood cell count when on Carbimazole?

Hello Everyone,

About 3-4 weeks ago I was diagnosed with Graves Disease. I had my first appointment with my Endocrinologist and he prescribed me with Carbimazole 20mg twice a day, along with Propranolol, because my levels were really high.

A few days after starting the Carbimazole I woke up with a mild sore throat and the next morning it was still there so I went straight to my Doctors for a full blood count test and stopped taking the Carbimazole immediately. My results came back the next day and showed that my white blood cell count was low. I was booked in for a blood test two days later after stopping the Carbimazole and those results showed that my white blood cell count had improved. My Endocrinologist rang me to discuss a new prescription of the Carbimazole at 5mg twice a day followed by a blood test in 7 days time and if the results were normal, to up my dosage by 10mg a day every week until I was on 40mg a day.

I have just had my 7 day blood test and the results have found that my white blood cell count is low again. I have been booked in for another blood test for 7 days time (Wednesday 30th) and I am keeping my dosage at 5mg twice a day, I won't increase the dosage.

I am debating whether I should wait to see what this next blood test result comes back with before ringing my Endocrinologist to update him or not.

I was just wondering if anyone else has been in this situation? What happened? What are the alternatives to Carbimazole, my Endocrinologist mentioned a thyroidectomy but I fear that might be too drastic?

Any advice would be greatly appreciated!

Many thanks,

Ashley x

2 Replies

Ashley, Carbimazole can reduce WBC which means you will be unable to fight off infection. Propythiouracil (PTU) is a second choice anti-thyroid drug for pregnant women and people unable to take Carbimazole but it can raise liver enzymes. If you are unable to take Carbimazole or PTU thyroidectomy is your only option.


Hi I had a bad reaction to Cabrimazole and am now on PTU and doing fine I have been on it now for six months and everything is fine.


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