Patients with adrenal insufficiency (AI) require additional glucocorticoid doses during surgery or medical illness, but there is no universally accepted regimen for glucocorticoid supplementation therapy. The high doses and long duration of glucocorticoid coverage that have traditionally been used do not reflect the hypothalamic-pituitary-adrenal response to surgical stress and medical illness in normal people. While the optimal dose and duration of supplementation therapy have not been established, our recommendations are based on extrapolation from what constitutes a normal cortisol response to stress, on expert opinion derived from the medical literature, and on clinical experience. The recommended use of lower doses of glucocorticoids during surgical and medical stress should not de-emphasise the importance of additional supplementation during such events. Our recommendations do not replace clinical judgement, but their use will ensure that patients with AI are safely managed during illness or surgery without the risk of an adrenal crisis or excessive steroid dosing.