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Thyroid UK
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Carbimazole and WBC

Has anyone had any actual experience with decreased WBC on Carbimazole? my understanding is that if you are affected, it happens quite quickly - within a few weeks of starting. My GP did a FBC a while after I started on Carb, but not since. I've been on them for 6 months now and my own blood tests have shown a slight decline in White cells.

Test results:


WHITE CELL COUNT 4.7 x10^9/L 3.00 -10.00

NEUTROPHILS 2.16 x10^9/L 2.00 -7.50

LYMPHOCYTES 1.84 x10^9/L 1.20 -3.65

MONOCYTES 0.46 x10^9/L 0.20 -1.00

EOSINOPHILS 0.19 x10^9/L 0.00 -0.40

BASOPHILS 0.02 x10^9/L 0.00 -0.10


WHITE CELL COUNT 4.0 x10^9/L 3.00 -10.00

NEUTROPHILS *1.80 x10^9/L 2.00 -7.50

LYMPHOCYTES 1.68 x10^9/L 1.20 -3.65

MONOCYTES 0.40 x10^9/L 0.20 -1.00

EOSINOPHILS 0.10 x10^9/L 0.00 -0.40

BASOPHILS 0.03 x10^9/L 0.00 -0.10

I'm going to test again tomorrow morning.

Does anyone have any comments on these results?

9 Replies

Me!! Yes this happened to me; but it also did it with PTU which is why I ended up having to have a thyroidectomy


Thanks for replying. I'm really hoping it doesn't come to that - I'm quite attached to my thyroid!


Wish I hadn't had mine taken out to be honest!! I'd look into mineral deficiencies including iodine and magnesium and also vit D and iron.

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I've tested for Vits and the only one I'm low on is Folate, with I'm supplementing. :)


Minerals are key though! They don't test for magnesium deficiency properly in this country. They do a blood test for serum magnesium instead of RBC magnesium so we don't get to see the real picture of how much magnesium is in the cells


I've not been tested for magnesium, but it is something I have been supplementing for a long time so I doubt it's low.


My WBC and neutrophils dipped slightly below the minimum level within a month of starting the Carbimazole, but went back to normal in month 2. Are you on a high dose (Carbimazole does suppress the immune system a bit) ?


Was on 40mg and went down to 20mg. when my FT4 was at mid range my gp seemed to think "my work here is done", even though TSH was over 8. I did my own tests as I had hypo symptoms. My T3 was at the bottom of the range so I dropped my Carb dose to 15mg and added the Folate supplement. I'll need to re test T3 in a couple of weeks.


Yes with a TSH of 8 and T3 at bottom of the range, the dose is too high and you were right to reduce. Aim to have a blood test every 8 weeks at least; there may be scope to reduce further. Keep an eye on your WBC/neutrophils to see if they go down further.

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