Management of Carbimazole with Normal Thyroid Function
Direct Recommendation
Maintain your current dose of carbimazole 5mg every other day and recheck thyroid function tests (TSH and FT4) in 4-6 weeks, with consideration for dose reduction or discontinuation if thyroid function remains stable.
Rationale for Current Dose Maintenance
Your thyroid function tests showing normal TSH and FT4 indicate you are currently euthyroid (biochemically controlled) on your present regimen. However, this does not automatically mean you should stop or reduce carbimazole immediately, as the underlying hyperthyroid condition may still be active.
Monitoring Frequency
- Repeat thyroid function tests every 4-6 weeks while on this low maintenance dose to ensure stability 1
- Once thyroid function remains consistently normal for several months, testing intervals can be extended to every 6-12 months 2
- If you develop any symptoms of hyperthyroidism (palpitations, tremor, weight loss, heat intolerance) or hypothyroidism (fatigue, weight gain, cold intolerance), recheck immediately 1
When to Consider Dose Reduction
You should consider reducing or discontinuing carbimazole if:
- TSH begins to rise above the normal range with normal or low FT4, suggesting you are becoming over-treated 1
- Thyroid function remains stable (normal TSH and FT4) for 3-6 consecutive months on the current minimal dose 3, 4
- You develop symptoms of hypothyroidism 1
Important Clinical Context
The very low dose you're taking (5mg every other day, equivalent to approximately 2.5mg daily) suggests you are in a late maintenance phase of treatment. Research shows that some patients with Graves' disease can be maintained on doses as low as 0.7-3.2mg daily 5, which is comparable to your current regimen.
Critical Pitfall to Avoid
Do not abruptly discontinue carbimazole without medical supervision, even with normal thyroid function tests. The underlying autoimmune process in Graves' disease (if that is your diagnosis) may still be active, and stopping treatment prematurely can lead to relapse of hyperthyroidism 5, 4. The typical treatment duration for Graves' disease is 12-18 months before attempting discontinuation.
Signs You May Be Over-Treated
Watch for development of:
- Rising TSH above normal range
- Falling FT4 below normal range
- Symptoms of hypothyroidism (fatigue, weight gain, cold intolerance, constipation)
If any of these occur, reduce the carbimazole dose further (perhaps to 5mg twice weekly) or discontinue entirely, and recheck thyroid function in 2-3 weeks 1.
Next Steps Algorithm
- Continue current dose of carbimazole 5mg every other day
- Recheck TSH and FT4 in 4-6 weeks 1
- If still normal: Continue same dose and recheck in another 4-6 weeks
- If TSH rising or symptoms of hypothyroidism: Reduce to 5mg twice weekly or stop, recheck in 2-3 weeks
- After 3-6 months of stability: Discuss with your physician about attempting discontinuation with close monitoring 3