ACTH Stimulation Test: What It Is, Why It's Done, and What Your Results Mean

When your body doesn’t make enough ACTH, a hormone made by the pituitary gland that tells your adrenal glands to release cortisol. Also known as adrenocorticotropic hormone, it’s the key signal that keeps your stress response and energy levels balanced. If your cortisol is low, doctors use the ACTH stimulation test, a simple blood test that checks how well your adrenal glands respond to synthetic ACTH. This isn’t a routine checkup—it’s used when something’s off with your energy, blood pressure, or stress handling. Think fatigue that won’t quit, dizziness when standing, or unexplained weight loss. These aren’t just "feeling tired" signs—they can point to adrenal insufficiency or pituitary problems.

The test works by giving you a shot of synthetic ACTH, then measuring your cortisol, the main stress hormone your adrenal glands produce. levels before and after. If your cortisol stays low, your adrenals aren’t responding. That could mean Addison’s disease. If cortisol jumps but you still feel awful, your pituitary might not be sending the right signal. The test also helps rule out problems caused by long-term steroid use, which can shut down your natural hormone production. It’s not about guessing—it’s about seeing if your body’s alarm system still works when you flip the switch.

You won’t need to fast or change your routine much, but your doctor will ask you to skip certain meds that mess with results—like steroids or birth control pills. The whole thing takes about an hour. Two blood draws, a quick injection, and you’re done. No needles in your spine. No scans. Just real data about how your body handles stress.

What you find matters. Low cortisol after the test? That’s not normal. It means your adrenals are worn out or damaged. High cortisol? That’s usually good—it means your system still has some fight left. But if your ACTH is high and cortisol stays low, you’ve got primary adrenal failure. If both are low, your pituitary might be the issue. These aren’t just lab numbers—they’re clues to why you feel so drained.

The posts below cover real-world cases where hormone imbalances show up in unexpected ways—from lithium affecting thyroid function to PPIs messing with vitamin levels. They all tie back to one thing: your body’s systems are connected. When one part falters, others react. The ACTH stimulation test is one of the clearest tools we have to see if your adrenal system is still speaking up. Below, you’ll find guides on how to interpret test results, what medications can interfere, and how to manage conditions that mimic adrenal fatigue. No fluff. Just what you need to understand your body’s signals and talk to your doctor with confidence.