Cortisol, often recognized for its role in the body’s stress response, is a steroid hormone produced by the adrenal glands, located atop the kidneys. This hormone influences nearly every organ and tissue, playing a part in a wide array of bodily functions. Beyond its involvement in managing stress, cortisol helps regulate blood sugar levels, influences metabolism by affecting how the body uses carbohydrates, fats, and proteins, and contributes to maintaining blood pressure. It also possesses anti-inflammatory properties and helps control the sleep-wake cycle.
The Body’s Cortisol Rhythm
Cortisol levels naturally fluctuate throughout the day, following a distinct pattern known as a circadian rhythm. This rhythm is primarily regulated by the body’s internal clock and is synchronized with the environmental day-night cycle. Cortisol levels typically begin to rise in the second half of the night, reaching their highest point in the early morning, usually around 8 to 9 AM. This morning surge in cortisol, often referred to as the “cortisol awakening response” (CAR), is a natural physiological event.
The CAR involves a sharp increase in cortisol levels, often by an average of 50%, within the first 30 to 45 minutes after waking. This increase helps prepare the body for the demands of the upcoming day, promoting wakefulness, alertness, and metabolic readiness. Following this morning peak, cortisol levels gradually decline throughout the day, reaching their lowest point around midnight. This pattern supports the body’s transition from activity to rest and recovery.
Understanding Normal Morning Levels
Normal morning cortisol levels vary depending on the test type and laboratory. “Normal” is typically a range, not a fixed number, and can be influenced by individual factors like age.
For blood tests, typically collected between 6 AM and 8 AM, a normal range is approximately 10 to 20 micrograms per deciliter (mcg/dL). These values generally signify healthy adrenal function and a well-regulated stress response. Saliva tests, measuring free cortisol, commonly show morning ranges of 10.2 to 27.3 nanograms per milliliter (ng/mL) or 3.2 to 22.8 nmol/L when collected between 7 AM and 9 AM. A 24-hour urine collection, reflecting total daily cortisol, typically ranges from 10 to 55 micrograms per day (mcg/day) for adults.
How Morning Cortisol is Measured
Morning cortisol levels are commonly measured using blood, saliva, or 24-hour urine tests. Each method assesses cortisol production and often requires specific timing to capture the morning peak.
A blood test involves a healthcare professional drawing a sample from a vein, typically between 8 AM and 9 AM, when cortisol levels are highest. For a saliva test, samples are collected at home using a swab or by spitting into a container, often in the early morning.
To ensure accuracy, avoid eating, drinking, or brushing teeth for at least 30 minutes before collecting a saliva sample. A 24-hour urine test requires collecting all urine produced over a full day and night, providing an overall picture of cortisol excretion. For this test, the first morning urine is typically discarded, and all subsequent urine is collected in a special, often refrigerated, container.
What Influences Morning Cortisol Readings
Several non-pathological factors can influence morning cortisol readings, potentially leading to results outside typical ranges. Stress, both acute (like test anxiety) and chronic, can elevate or alter cortisol patterns. Irregular sleep or sleep deprivation significantly impacts cortisol rhythms, affecting morning levels. Certain medications, such as oral contraceptives, corticosteroids, antidepressants, and stimulants, can influence cortisol levels. Strenuous exercise before a test can temporarily elevate cortisol, making it important to follow any preparation instructions.