Your stated morning-or-evening type is a direction, not a clock time
When researchers compare what people say about themselves with what their bodies actually do, the two tend to agree on direction but not on precision. In young and older adults, self-reported preference for morning or evening activity was related to the measured phase of the plasma melatonin rhythm and the core body temperature rhythm [5]. In a modified constant-routine study, morning and evening chronotypes differed in the circadian rhythms of temperature, melatonin, and sleepiness [4]. In other words, someone who calls themselves a night owl really does tend to have a later-running internal clock than someone who calls themselves a morning person.
The catch is that "later" is not the same as "this many hours later." These studies establish an association between self-report and measured phase, not a conversion formula. A person's stated chronotype tells you which way their rhythm leans; it does not reliably tell you when their melatonin will rise. That distinction matters whenever timing is the point, such as scheduling light exposure, sleep, or medication.
What home melatonin testing actually measures, and how far off it can be
The standard objective marker is dim-light melatonin onset, or DLMO: the moment melatonin starts rising in the evening under low light. In a self-directed at-home DLMO pilot, measured DLMO times were on average 3 hours and 18 minutes earlier than participants' self-reported sleep onset [1]. That gap is a concrete illustration of the mismatch: sleep onset is a behavior, DLMO is a hormonal phase marker, and the two are not interchangeable.
A later contactless, self-directed home protocol also collected circadian phase and compared it with self-reported bedtime over the preceding five days [2]. The abstract reports the protocol as feasible, but the comparison is between measured phase and reported bedtime, not a demonstration that self-report can substitute for measurement. The practical reading is that home sampling can give you an objective phase estimate, while your own report of when you sleep is a separate and looser piece of information.
Can at-home testing replace the lab?
The home-based approach has been shown to work in principle. The self-directed at-home DLMO pilot demonstrated feasibility and accuracy of home-based testing [1], and the contactless home protocol was likewise reported as feasible [2]. In a real-world clinical population, home-based self-collected salivary assessments produced circadian phase profiles, and among 161 patients with atypical profiles who reported symptoms before sampling, the phase profiles were concordant with at least one presenting complaint in 93.8% of cases [3]. That high concordance suggests the home-collected phase information was meaningful enough to line up with clinical complaints, though it describes agreement with symptoms rather than validation against a laboratory standard.
What these studies do not provide is a direct head-to-head test showing that home DLMO matches lab DLMO closely enough to be swapped in. The evidence is feasibility and internal consistency in pilot and clinical settings, not equivalence. So home testing looks promising as a practical way to get an objective phase estimate outside a lab, but calling it a replacement for laboratory protocols goes beyond what has been shown.
What to take away if you want to know your own timing
If your question is simply "am I a morning person or a night person," your own preference is a reasonable starting signal, backed by the consistent direction of the chronotype findings [4][5]. If your question is "when exactly does my circadian night begin," self-report is not enough, because reported sleep onset and measured DLMO can differ by hours [1].
Home-based melatonin sampling is the middle path: it can yield an objective phase estimate without a lab visit, and the pilot and clinical work supports that it is doable and produces coherent results [1][2][3]. The honest caveat sits right next to that conclusion: the evidence base is small and focused on feasibility, so treat home results as a useful objective estimate rather than a certified stand-in for a laboratory measurement.
Sources used in this answer
Self-directed home-based dim-light melatonin onset collection: The circadia pilot study
In a self-directed at-home DLMO pilot, measured DLMO times averaged 3 hours and 18 minutes earlier than self-reported sleep onset, and the home-based design was reported as feasible and accurate.
Feasibility of a contactless, self-directed, home-based dim-light melatonin onset protocol: the Circadia pilot study
A contactless, self-directed home-based DLMO protocol was reported as feasible, collecting circadian phase and comparing it with self-reported bedtime over five days.
Dim Light Melatonin Onset Profile Phenotypes in a Real-World Clinical Population with Home-Based, Self-Collected Salivary Assessments: Identification, Distribution …
In a real-world clinical population using home-based self-collected salivary assessments, circadian phase profiles were concordant with at least one presenting complaint in 93.8% of 161 patients with atypical profiles who reported symptoms before sampling.
Chronotype differences in circadian rhythms of temperature, melatonin, and sleepiness as measured in a modified constant routine protocol
Morning and evening chronotypes differed in circadian rhythms of temperature, melatonin, and sleepiness as measured in a modified constant routine protocol.
Relationship of endogenous circadian melatonin and temperature rhythms to self-reported preference for morning or evening activity in young and older people
Self-reported preference for morning or evening activity was related to the objectively measured phase of plasma melatonin and core body temperature rhythms in young and older people.