5mg carbimazole too much & 2.5mg too little

[Livsamfra]

Has anyone had trouble maintaining thyroid levels, 5 mg once daily drops my T4 below ideal but with 2.5 mg once daily my T4 climbs slowly over the months to too high. Has anyone ever taken 5mg for 5 days and then nothing for 2 days and repeat the same?

[PurpleNails Administrator]

welcome to forum.

Fine tuning low doses carbimazole is tricky. Most doctors think 5mg per day is lowest dose & next step stopping. but not the case.

Is FT3 being tested too?

Could you try alternating days.

Mon 5

Tue 2.5

Wed 5

Thu 2.5

Fri 5

Sat 2.5

Sun 5

Or if need adjusting add or decrease additional days.

How long have you been on carbimazole? Did you start on higher dose & work down.?

Was Graves confirmed with positive Trab & TSI antibodies (TPO & TGab are not specific to Graves).

There are other causes of hyper, some transient.

posting your results can help make sure we are giving you the correct interpretation. Always include lab ranges.

[Livsamfra in reply to PurpleNails]

Thank you so much for your reply. I was diagnosed Decmeber 2015 and been on Carbimazole since, except for the last 3 months of my pregnancy (nearly 4 years on Carbimazole) and 5 months postpartum. My T4 then started increasing again. For the first month after diagnosis in 2015 I was on 20mg per day, after that I have always been on 5mg and after 18 months I tried coming off but it wasn't successful. I feel my best when my T4 is between 12 and 13. When it goes below 12 I feel off and when it gets to 15 and above I also feel off. Last year I tried 5mg one day and 2.5mg the next day. When I tested the day after taking 2.5mg on 4 October 2022 my T4 was at 15.11 when I tested T4 again on 31 October after taking the 5mg I was at 11.16. So then I decided to take 3/4 of a 5mg tablet daily. When I tested T4 on the 24th November I was 14.23. At the same time I tested antibodies again after many months of not checking. Here they test Anti- TG antibody which was at 90.6 and Anti - TPO antibody which was at 27.24. I also tested TSH = 2.53 and T3= 4.67. I decided to continue with the 3/4 tablet daily to see if it would maintain at this as I was feeling fine. 5th of Jan this year, I tested T4 again and it was at 14.80, a slow climb from 14.23 but still a climb, so then I decided to go back to 5 mg per day. I checked T4 again 20 days later on the 25 Jan and it had dropped quickly to 12.31 which is my IDEAL but now I am really wanting to maintain it at this??? It just seems I respond so quickly to the carbimazole and it's now been 7 years that I have been on it, but just can't come off the carbimazole because on a very low dose my T4 still climbs very gradually. 5mg daily is too strong but 2.5 is just too little. Would 5mg once a day for 5 days in a row with a 2 day break in between be an approach I could try?

[Livsamfra in reply to Livsamfra]

PS I was diagnosed with Graves

[PurpleNails Administrator in reply to Livsamfra]

Can you add ranges ?

You are testing very quickly - you need at least 6 weeks to see how a dose adjustment will settle.  carbimazole works by inhibiting production so it might be weeks later the levels are affected.

 FT4 is low by most ranges but your FT3 might be disproportionately high, this can occur in 15% of hyperthyroid people. 

Breaks causes a longer window, allowing thyroid to produce.  Daily is better as slight variation would balance out. 

Although a 2 day a short break it is said ‘restarting’ carbimazole can trigger an increase in new side affects.  (this likely applies to longer gaps)

 5 day -x 5mg = 25mg per week.

3 day 5mg [15] & 4 days 2.5mg [10] would also total 25mg over the week.  

Doctors diagnose Graves on thyroid level, (low TSH) so unless correct antibodies tested I would seek evidence.  You only ever been on a very low dose, gradual rises - doesn’t sound like graves.   Graves typically need starting doses of 40mg and sudden spikes in levels.  

You sound like you may have nodule which fits with high FT3 elevated levels & nodules do not abate (remission not expected). Or you could be having fluctuation & times when hypothyroid. Are you testing under same conditions & time of day.   

We recommend draw booked on morning after fasting overnight.  

Please put country in profile.

[Livsamfra in reply to PurpleNails]

T4 range is : 9-19

T3 range is : 4-8.3

Based on the above ranges I would say my T3 is on the lower end and my T4 is close to mid range. When first diagnosed my TSH levels were undetectable they were so low and the antibodies they have always tested were the anti- TPO (thyroid peroxidase) and anti- TG (thyroid globulin). I had a scan of my thyroid 6 months after diagnosis and it was clear. Do you think I should go for another scan?

Testing same time of day, always before midday but not fasting, perhaps I should do it in a fasted state.

You mentioned it might take weeks for levels to be affected, yet mine are affected very quickly. Within 20 days this year I came down from 14.80 to 12.31.

Thanks for the dosing schedule, I think I will do that approach 3 days on 5mg and then 4 days on 2.5mg

[PurpleNails Administrator in reply to Livsamfra]

recommend test are closest to 09.00. This show highest daily TSH. FT4 is going to fluctuate daily anyway. So the small difference is not likely to be due to a dose reduction 4 days before.

what was in the scan report? Were there any comments about health, size and appearance of thyroid?

Positive TPO & TG antibodies confirms autoimmune is present. but Hashimoto’s causes transient hyper ultimately hypo. TSI & Trab confirm Graves. Ultrasound don’t determine function. Only nuclear uptake scan can show function throughout thyroid.

[Livsamfra in reply to PurpleNails]

Ultrasound scan was all normal for size and health etc and no nodules present. This was done in 2016. I have never been hypothyroid in the 7 years, so could Hashimoto's be possible? I will find out if a TSI and Trab test is available here and see if I can get it tested.

[PurpleNails Administrator in reply to Livsamfra]

where are you?

I know of private options in UK if NHS won’t test.

Other member know of options elsewhere.

[Livsamfra in reply to PurpleNails]

we live in Tanzania

[pennyannie]

Hello Livsamfra and welcome to the forum :

it can also depend on what stage / phase of the disease you are in :

We really need more details to help you better understand what is going on :

What have you been diagnosed with, how long have you been on the AT drug and what is the endocrinologists plan long term and what symptoms are you still struggling with ?

The most recent research is suggesting that if you are diagnosed Graves the longer the patient stays on the AT medication the better the option for the patient :

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

[SlowDragon Administrator]

Always test TSH, Ft4 and Ft3

Important to test vitamin D, folate, ferritin and B12 at least once year

What vitamin supplements are you currently taking

[helvella Administrator Thyroid UK]

Carbimazole has a short half-life.

This is why split dosing is often (usually? always?) advised when people start taking it. Otherwise, their thyroid can "escape" from the effects of Carbimazole before they take their next dose.

I don't think anyone really understands quite why low dose Carbimazole works as it seems to. But two days without any wouldn't appear to be an obvious approach.

I suggest you consider taking 2.5 milligrams a day - adding in a second dose around 12 hours later if you feel that one 2.5 mg dose isn't quite working. Maybe once every two, three, four, five days - whatever seems to work for you.

This is based on thinking and reading about the issues - not personal experience.

[Livsamfra in reply to helvella]

thank you for this. I think I’m going to try the following:

3 days x 5mg and then 4 days x 2.5mg OR 2 days x2.5 mg, 3 days x 5mg and then 2 days x 2.5mg