Salivary Melatonin Profile: How to Interpret Your Result

What the profile actually measures

Melatonin normally stays low during the biological day and rises during the biological evening. Saliva sampling provides a practical way to estimate that rhythm because salivary concentrations track the circulating signal. DLMO is widely used as an objective marker of the central circadian clock, as described in Measuring Dim Light Melatonin Onset in Humans.

A profile is not the same as a routine blood test with one population-wide reference interval. The curve is interpreted across time. The important questions are whether a clear rise occurred, when it crossed the laboratory's threshold, and how that time relates to the person's sleep schedule and symptoms.

Read the report in five steps

1. Confirm the assay and threshold

Look for the measurement method, reporting units, lower limit of quantification, and DLMO rule. Laboratories may use a fixed concentration threshold or a threshold calculated from early low samples. Those approaches can produce different onset times. In a 122-person analysis, hourly and half-hourly sampling were strongly correlated, but some individual estimates differed by more than 30 minutes; the threshold method also shifted the calculated onset. See Calculating the dim light melatonin onset: the impact of threshold and sampling rate.

Do not apply a threshold copied from another laboratory to the reported values. An immunoassay and a liquid chromatography tandem mass spectrometry method can have different analytical characteristics. The report's own validated method is the correct starting point.

2. Inspect the sampling window

The collection series needs to begin before the expected rise and continue long enough to capture it. If the first sample is already high, the onset may have occurred before sampling began. If the last samples remain low, onset may have occurred later. Either pattern can make the report indeterminate rather than biologically abnormal.

The 2024 international at-home protocol emphasizes lighting, sampling rate, sampling timing, assay methods, and documentation of adherence. It does not endorse interpreting a home value without those controls. See A Protocol to Determine Circadian Phase by At-Home Salivary Dim Light Melatonin Onset Assessment.

3. Check collection quality

Review the log for bright light, screen use near the face, food or drink close to a sample, tooth brushing, bleeding gums, tobacco or nicotine, and missed or delayed tubes. The specific restrictions should come from the laboratory because collection devices and assays differ. A result collected under ordinary bright room light should not be treated as equivalent to a dim-light protocol.

Also check whether the person changed time zones, worked a night shift, stayed up much later than usual, or substantially changed sleep timing before testing. These factors can change the rhythm being measured.

4. Compare DLMO with sleep timing

DLMO is most informative when paired with a sleep diary or actigraphy from the surrounding days. A late DLMO may be consistent with a delayed circadian phase when sleep onset and wake time are also delayed. An early DLMO may fit an advanced phase when sleepiness and waking occur unusually early. The diagnosis still depends on the recurring sleep pattern, functional consequences, duration, and exclusion of other causes.

The American Academy of Sleep Medicine guideline discusses timed light and melatonin for specific intrinsic circadian rhythm sleep-wake disorders. It does not say that every late laboratory curve requires melatonin or that every low concentration requires supplementation. See Clinical Practice Guideline for the Treatment of Intrinsic Circadian Rhythm Sleep-Wake Disorders: Advanced Sleep-Wake Phase Disorder (ASWPD), Delayed Sleep-Wake Phase Disorder (DSWPD), Non-24-Hour Sleep-Wake Rhythm Disorder (N24SWD), and Irregular Sleep-Wake Rhythm Disorder (ISWRD). An Update for 2015: An American Academy of Sleep Medicine Clinical Practice Guideline.

5. Decide whether the profile is interpretable

An interpretable profile has documented dim-light collection, enough valid samples, a measurable evening rise, and a threshold calculated by the laboratory's stated method. A flat, truncated, contaminated, or poorly documented curve may need repeat collection rather than a clinical label.

What “low melatonin” can mean

A low result can mean different things depending on where it appears on the curve:

• Low early-evening values may be expected before DLMO.
• An entirely low series may have ended before the person's biological evening.
• Bright light during collection may suppress or delay the measured rise.
• Assay sensitivity may be insufficient to define an onset in a low-amplitude profile.
• Recent schedule changes, medications, or individual variation may contribute.

Large pooled work demonstrates that DLMO varies with age, chronotype, method, and population. It also found substantial variability in peak melatonin values and cautioned against treating amplitude as a simple age-adjusted diagnosis. See The dim light melatonin onset across ages, methodologies, and sex and its relationship with morningness/eveningness.

A low curve does not by itself diagnose pineal failure, insomnia, depression, or a genetic circadian disorder. It also does not establish a melatonin dose.

What “high melatonin” can mean

A high evening sample may simply show that the biological night started earlier than expected. Recent melatonin use can also raise salivary values and obscure endogenous onset. The product, dose, formulation, and time taken should be documented, but decisions about holding a prescribed product before retesting should come from the ordering clinician and laboratory.

A single high point should first prompt a review for labeling errors, contamination, timing, and supplement exposure. The test is not validated as a stand-alone screen for pineal tumors, endocrine tumors, or toxicity. Claims that a particular salivary concentration automatically requires brain imaging are not supported by DLMO methodology.

Why there is no single normal range

“Normal” depends on what is being compared. Clock time varies with habitual sleep, age, chronotype, latitude, season, and study method. Concentration varies by assay. A DLMO at 10 p.m. can be well aligned for one sleep schedule and poorly aligned for another.

The most useful interpretation states:

1. the laboratory method and threshold;
2. the calculated DLMO and its confidence or uncertainty;
3. whether sampling captured the rise;
4. the habitual and target sleep windows;
5. relevant light, medication, supplement, and schedule factors; and
6. whether the result supports, contradicts, or fails to resolve the clinical question.

Questions to bring to the ordering clinician

• Which threshold did the laboratory use, and why?
• Did the curve begin low and cross the threshold clearly?
• Were any samples excluded or below the assay's quantification limit?
• How does DLMO relate to sleep onset on the diary or actigraphy record?
• Could light exposure, supplements, medication, or an altered schedule explain the shape?
• Would repeating the collection under stricter conditions change management?
• If treatment timing is considered, what diagnosis and goal is being treated?

These questions make the test clinically useful without turning one saliva number into a disease label or a self-directed treatment protocol.