High dose intravenous glucocorticoid pulse (i.v. GCS) therapy is a proven approach in patients with active, moderate to severe Graves' orbitopathy (GO) and dysthyroid optic neuropathy (DON). In moderate to severe GO, the European Group on Graves' Orbitopathy (EUGOGO) recommends a 12-week course of intravenous methylprednisolone (i.v. MP) pulse therapy with a cumulative dose of 4.5 g. The response rate of i.v. GCS treatment is significantly higher than oral glucocorticoid (oral GCS) therapy and is associated with fewer adverse events. However, a major concern was raised because of reports of fatal side effects which may be associated with this therapy, especially when single and cumulative doses of methylprednisolone (MP) are higher than recommended. The prevalence and severity of adverse effects during treatment have not been fully described. The aim of this review was to summarise the frequency of major adverse effects of i.v. GCS compared to oral GCS and attempt to propose some practical suggestions as to how to monitor and prevent the development of side effects.