Abstract Disclosure: K.S. Wei: None. M.O. De La Torre: None. A. Flores: None. C.E. Chiu: None. T.E. Angell: None. Introduction: Over the counter (OTC) health supplements are commonly used by patients for a variety of ailments but may contain active ingredients that are not stated, such as glucocorticoids. Here, we present a case series of 12 patients seen by the Endocrinology Consult service at an urban safety net hospital during 2022-2023 and determined to have iatrogenic adrenal insufficiency (AI) from specific OTC supplements that surreptitiously contained glucocorticoids. Clinical Cases:12 patients using OTC arthritis supplements [Artri King (n=8), Ardosons (n=3), and Ajo Rey (n=1)] were identified. Median age was 52 years and 33.3% were female. All started using the supplements because of joint pain. Median length of use prior to cessation was 6 months. The most common presenting symptoms were nausea/vomiting (42%), fatigue (42%), abdominal pain (33%), and dizziness (17%). The most common physical exam findings of steroid excess included moon facies (66%), central adiposity (66%), abdominal striae (50%), dorsocervical fat pad (33%), and bruising (33%). 3/12 patients required ICU admission. Cortisol assessment was performed in 11/12 patients, which showed normal cortisol level in 1 patient (cortisol ≥16 mcg/dL), AI in 3 patients (cortisol ≤3 mcg/dL), and an equivocal level (cortisol 3-16 mcg/dL) in 7 patients. Cosyntropin stimulation testing in 6/7 patients with equivocal cortisol levels suggested AI in 4 (cortisol level <16 mcg/dL at 60 minutes after ACTH stimulation), whereas 2 showed lower but normal response (cortisol levels 18.2 mcg/dL and 18.4 mcg/dL). In total, 10/12 patients were prescribed glucocorticoid tapering replacements to avoid precipitating adrenal crisis. The most common regimens were hydrocortisone 20mg qAM/10mg qPM (33%) and hydrocortisone 5mg qAM/5mg qPM (17%). To date, 2/10 patients have successfully discontinued steroid replacement. Conclusion: These cases demonstrate possible Cushing’s syndrome and/or adrenal insufficiency after unintentional exposure to glucocorticoids in these OTC arthritis supplements, which has only previously been reported in a small number of case reports (1). This series collected over a 2-year period offers important clinical insights: Because patients may not identify or recall a supplement, possible use of OTC medications for arthritis or other anti-inflammatory purposes should be specifically assessed in patients presenting with adrenal insufficiency (especially with concomitant findings suggesting Cushing’s syndrome). For patients on such supplements, immediate discontinuation may not be possible without cortisol replacement and should be done with caution. 1)Boncompagni A.C. et al. A case of iatrogenic Cushing syndrome and subsequent adrenal insufficiency from a hidden ingredient in the supplement Artri Ajo King. J Am Coll Emerg Physicians Open. 2023;4(4):e13007. Presentation: 6/1/2024