ACTH (Cosyntropin/Cortrosyn) Dosage Calculator

Cosyntropin comes in a 0.25 mg vial. Reconstitute with 1 mL of normal saline (0.9% NaCl), not bacteriostatic water. The manufacturer is specific about this. You'll draw up the entire 1 mL for the full 250 mcg diagnostic dose. There's no partial dosing for adults. The timing matters more than most people realize. Morning testing (8-9 AM) is preferred because cortisol follows a diurnal rhythm; afternoon testing can produce misleading baseline values. Draw your baseline cortisol before touching the cosyntropin. Then collect at both 30 and 60 minutes. Some patients with intact adrenal function peak late, and calling it a failure based on one timepoint is a common diagnostic error. Stop glucocorticoids on the day of testing. Estrogen-containing drugs need a 4-6 week washout because they raise cortisol-binding globulin. Miss that detail and you'll get a falsely raised total cortisol reading. Use reconstituted cosyntropin immediately. Don't store it. Don't batch it. One vial, one test, one patient.