Traditionally, cortisol and ACTH levels (separate lavender top tube) are drawn at baseline (time = 0). Next, synthetic ACTH or another corticotropic agent is injected IM or IV, depending on the agent.[12] Approximately 20 mL of heparinized venous blood is collected at 30 and 60 minutes after the synthetic ACTH injection to measure cortisol levels.[13][14]