Cortisol
Here’s what it reflects — and what to do about it.
Longetic pulls together every lab and record you’ve had, follows how Cortisol changes over time, and explains what’s shifting — so you walk into your next appointment prepared, with reminders for retests along the way.
What is Cortisol?
The body's primary stress hormone, produced by the adrenal glands.
Cortisol regulates metabolism, blood sugar, and blood pressure, and drives the body's stress response. It follows a diurnal rhythm: levels are highest shortly after waking (typically peaking around 6-8am) and decline through the day to their lowest point around midnight.
What to know about Cortisol
Understanding Cortisol means knowing what it reflects, what tends to move it, and the signs that suggest it’s worth a closer look — so you can bring the right questions to your next appointment.
How to read a value in context
Cortisol's reference range reflects the wide natural swing this hormone takes over a single day, so 'normal' is a broad, time-of-day-dependent statistical band rather than a personalized target. It's possible to feel wired, exhausted, or anxious while a one-time cortisol result still falls in range, partly because cortisol shifts with sleep, stress, and even the time of the blood draw.
Lifestyle factors that influence this marker
- Keep a consistent sleep and wake schedule
- Practice regular stress-management techniques like breathing
- Limit late-day caffeine and alcohol intake
- Talk to your doctor before making changes based on this result.
Tests often checked alongside this
- ACTH — helps identify whether the issue starts in the adrenal glands or the pituitary
- DHEA-S — another adrenal hormone used to assess overall adrenal function
- Free cortisol (saliva or urine) — captures patterns a single blood draw can miss
How this can show up in how you look and feel
- High cortisol can be associated with weight gain around the face or midsection
- Some people notice thinner skin or easier bruising with prolonged elevation
- Poor sleep and mood changes like anxiety can be associated with cortisol imbalance
- Low cortisol is sometimes associated with fatigue and low blood pressure
What can affect this marker
- Time of day it's measured
- Sleep quality and stress levels
- Certain medications, like steroids
- Biotin supplements before testing
What to track over time
- Your rhythm across the day
- Trend across repeat morning tests
- Sleep and stress patterns
- Alongside energy and mood changes
What to ask your doctor
- Was this test timed correctly?
- Should I check my rhythm across the day?
- Could stress be skewing this result?
- Do I need further hormone testing?
This glossary entry is for informational purposes only and is not a substitute for professional medical advice. Read our Medical Disclaimer.
References
About our sources
Official sources
Government health agencies, national institutes, and intergovernmental bodies whose guidelines carry regulatory or policy weight.
Clinical / professional
Medical societies, specialty colleges, and professional associations whose consensus statements reflect clinical practice standards.
Peer-reviewed research
Original research articles and systematic reviews published in indexed journals and verified through PubMed or DOI.