Patients with Graves' disease who stop anti-thyroid drugs before 18 months of treatment are more likely to experience a return of the disease than those who complete at least 18 months of therapy.

We analyzed the available evidence on how long anti-thyroid drugs should be taken for Graves’ disease to reduce the chance of symptoms returning. What we’ve found so far suggests that stopping treatment before 18 months is linked to a higher chance of the disease coming back compared to continuing for at least 18 months [1]. This pattern was observed across all the studies we reviewed, with no evidence contradicting it. Anti-thyroid drugs work by reducing the overproduction of thyroid hormones in Graves’ disease, a condition where the immune system mistakenly attacks the thyroid. The goal of treatment isn’t just to control symptoms temporarily, but to give the body a chance to reset its immune response. The evidence we’ve reviewed indicates that staying on these medications for 18 months or longer may help the body reach a more stable state, making it less likely for the disease to return after stopping. We don’t know why 18 months appears to be a meaningful threshold, or whether longer treatment—say, 24 or 36 months—offers even better results. The evidence we’ve seen doesn’t address those longer durations. It also doesn’t explain whether factors like age, severity, or antibody levels change this pattern. For now, the clearest pattern in the data is that treatment shorter than 18 months tends to be followed by a return of symptoms more often than treatment that reaches or exceeds that mark. If you’re taking anti-thyroid drugs for Graves’ disease, staying on them for at least 18 months may help lower the chance that your symptoms come back after you stop. But always talk with your doctor before making any changes to your treatment plan.