Cortisol (PM): Evening Stress Hormone, Sleep Signal, and What High or Low Means
Overview
Cortisol (PM) measures your cortisol level later in the day, when it should be trending low. It is used to check whether your stress hormone rhythm is tapering like it should as evening approaches. A higher than expected PM cortisol can show up with chronic stress, sleep disruption, certain medications, or endocrine conditions. A lower than expected value can show up when adrenal output is suppressed or when timing and context matter. In this glossary you will see what PM cortisol reflects, how it compares with Cortisol (AM), how brain signaling through Adrenocorticotropic Hormone (ACTH) fits in, what can push PM cortisol off track, and how lifestyle levers like a Circadian Rhythm Reset often relate to the bigger picture.
What evening cortisol is and why it matters
Cortisol is made by your adrenal glands and follows a daily rhythm. In a typical pattern:
Cortisol is highest in the early morning to help you wake up and mobilize energy
It gradually declines through the day
It reaches its lowest levels at night to support winding down and sleep
Cortisol (PM) is a blood test taken in the afternoon or evening to capture that lower phase. It helps show whether the system is tapering normally or staying unusually elevated late in the day.
Because cortisol is so tied to time, a PM value is only meaningful if the draw time is clear and consistent, and if you interpret it alongside morning cortisol and symptoms.
What your Cortisol (PM) result can tell you
Your PM cortisol value can help answer questions like:
Is my cortisol rhythm shutting down properly by evening
Could my late day wired feeling, insomnia, or night waking have a stress hormone component
Does my cortisol pattern match stress load, training, illness, or medications
Cortisol (PM) is often used with a morning cortisol test. If morning cortisol is normal but PM cortisol stays high, it can suggest a flattened rhythm where cortisol is not tapering well. If both AM and PM cortisol are low, clinicians think about adrenal suppression or pituitary signaling issues.
How to read high and low Cortisol (PM)
PM cortisol is mostly about whether the taper looks normal.
When Cortisol (PM) is high
Higher than expected PM cortisol often means your body is not coming down into the evening the way it should. Common reasons include:
Chronic psychological stress, anxiety, or high life load
Poor sleep timing, late screens, irregular schedules, or night shift patterns
Overreaching training blocks with limited recovery
Stimulant use late in the day
Medications that raise cortisol or change how it is measured
Less commonly, endocrine conditions that push cortisol production higher
Possible effects can include trouble falling asleep, waking up at night, feeling tired but wired in the evening, and harder recovery after training. This does not automatically mean disease, but persistent high PM cortisol with symptoms is worth addressing.
When Cortisol (PM) is low
Lower PM cortisol is often normal, since evening is supposed to be low. It becomes meaningful mainly when:
It is low together with low morning cortisol
Symptoms suggest adrenal insufficiency, such as deep fatigue, low blood pressure, dizziness on standing, or low stress tolerance
Steroid medications have recently been used and may be suppressing cortisol output
In most cases, a low PM cortisol alone is not a problem. The pattern across the day matters more than any single evening value.
What can affect your Cortisol (PM) result
PM cortisol is sensitive to real life inputs and timing.
Common influences include:
Sleep schedule and circadian alignment
Irregular bedtimes, late meals, night shift work, or poor light timing can push cortisol later into the day.Stress and mental load
High workload, relationship stress, or prolonged anxiety can keep cortisol elevated into the evening.Training volume and recovery
Hard blocks with low recovery, especially combined with under fueling, can flatten the cortisol curve and keep PM levels higher.Medications and supplements
Steroids taken in any form can suppress your own cortisol production. Some antidepressants, stimulants, and hormone products can alter levels or interpretation.Illness and inflammation
Acute infections or chronic inflammatory states can raise cortisol throughout the day as the body tries to cope.Timing of the draw
A draw at 3 p.m. and a draw at 9 p.m. are not the same signal. Consistency is key when tracking patterns.
When to talk to a clinician about Cortisol (PM)
You should review your PM cortisol with a clinician when:
PM cortisol is clearly high on repeat tests and you have sleep disruption, anxiety, or unexplained fatigue
Your AM and PM cortisol pattern looks abnormal together
You are taking or recently stopped steroid medications
Symptoms suggest adrenal insufficiency or endocrine overproduction
You have known pituitary or adrenal conditions
A clinician can place PM cortisol next to AM cortisol, ACTH, metabolic markers, blood pressure, medication history, and your symptom story. If needed, they can order rhythm focused testing or stimulation and suppression tests to see how the system responds, not just what a single point looks like.
Cortisol (PM) in one view
Cortisol (PM) is an evening snapshot of your main stress hormone and a check on whether your daily cortisol rhythm is tapering the way it should. High PM cortisol often reflects stress, sleep or circadian disruption, heavy training load, or medication effects, while low PM cortisol is usually normal unless the whole day pattern is low. Interpreted with morning cortisol, ACTH, and your real world symptoms, it becomes a useful guide for when recovery, sleep timing, and stress support may be enough and when deeper endocrine review is needed.
