Melatonin: Levels, Ranges, and What They Mean

What Is Melatonin?

Melatonin is a hormone produced primarily by the pineal gland, a small structure deep within the brain. It plays a central role in regulating your circadian rhythm — the internal 24-hour clock that governs your sleep-wake cycle. Melatonin production is closely tied to light exposure: levels typically rise in the evening as darkness sets in, peak in the middle of the night, and fall toward morning as light returns.

Because of this pattern, melatonin is often called the “darkness hormone” or “sleep hormone.” Beyond signaling that it is time to sleep, melatonin may also influence body temperature, blood pressure regulation, immune function, and antioxidant activity. Its production tends to decline with age, which is one reason older adults sometimes notice changes in sleep quality.

Melatonin does not work in isolation. It interacts with other hormones and with environmental cues such as light, meal timing, and physical activity, making it one piece of a larger picture of metabolic and hormonal balance.

What the Test Measures

A melatonin test measures the concentration of the hormone in your body, usually in blood, saliva, or urine. Because melatonin levels change dramatically over the course of a day, the timing of the sample is critical to interpretation.

Most testing focuses on capturing the natural rhythm of melatonin rather than a single snapshot. Some tests look at the overnight peak, while others measure a metabolite of melatonin in urine collected over a set period. Your clinician will choose the method and timing based on what they are trying to understand about your sleep and hormone patterns.

Melatonin Reference Ranges

Reference ranges for melatonin vary considerably by laboratory, sample type, time of collection, and the method used to measure it. The values below are commonly cited general ranges for blood (serum) melatonin and should be viewed as approximate guidance only.

These numbers are illustrative. Each laboratory establishes its own reference intervals based on its equipment and tested population, so always interpret your result against the range printed on your specific lab report.

What High Levels Can Mean

Elevated melatonin levels — particularly when measured at times of day when they would normally be low — may have several explanations. Some possibilities your clinician may consider include:

• Supplementation with melatonin, which is the most common reason for high readings
• Timing of the sample during the natural overnight peak
• Reduced clearance of the hormone, which can occur with certain liver conditions
• Some pineal-related conditions, though these are uncommon

A high reading is not automatically a problem. Context — including whether you take supplements, when the sample was drawn, and how you are sleeping — matters a great deal. High melatonin may sometimes be associated with daytime drowsiness or grogginess, but interpretation should always be made by a qualified professional.

What Low Levels Can Mean

Lower-than-expected melatonin, especially during the overnight hours when production should be at its highest, may be linked to:

• Aging, as natural melatonin output often declines over time
• Exposure to artificial or blue light in the evening, which suppresses production
• Shift work or irregular sleep schedules that disrupt circadian rhythm
• Certain medications or substances that interfere with melatonin signaling
• Some chronic health and neurological conditions

Low melatonin can sometimes accompany difficulty falling asleep, fragmented sleep, or a sense that your internal clock is out of sync. However, sleep problems are multifactorial, and a single low value does not establish a diagnosis on its own.

How the Test Is Done

Depending on the approach your clinician recommends, melatonin testing may involve one of the following:

• Blood (serum) test: A standard blood draw, often timed to capture either daytime or overnight levels. Multiple samples may be needed to map the rhythm.
• Saliva test: A non-invasive option in which you collect saliva at specified times, frequently in the evening, to observe the rise in melatonin.
• Urine test: Measures a melatonin metabolite, sometimes collected overnight or across a 24-hour period to estimate total production.

Because light exposure strongly affects melatonin, you may be asked to follow specific instructions, such as collecting samples in dim light or avoiding certain activities beforehand. Following these directions carefully helps ensure your result reflects your true physiology.

Putting Your Number in Context

A single melatonin value is most useful when interpreted alongside your symptoms, sleep habits, lifestyle, and other relevant lab work. At ENNU Life, we emphasize looking beyond whether a number simply falls inside a broad “normal” range. We consider what an optimal range may look like for your individual goals and how your values move over time.

Trends often tell a richer story than any isolated result. Tracking melatonin and related markers across multiple time points can reveal patterns — such as a blunted overnight rise or a shifted rhythm — that a one-time reading might miss. This longitudinal view supports more personalized, proactive care.

It is also important to remember that reference ranges differ between laboratories and that melatonin is highly sensitive to timing, light, and supplementation. For these reasons, your result should always be reviewed with your clinician, who can place it in the full context of your health history and help you decide whether any further evaluation or adjustment is appropriate.