The dim light melatonin onset, melatonin assays and biological rhythm research in humans

Alfred J. Lewy

Research output: Contribution to journalArticle

50 Scopus citations


The most useful marker for human circadian phase position is the dim light melatonin onset (DLMO). This is optimally obtained by sampling blood or saliva in the evening at intervals of 30 min or less. Ambient light intensity should not exceed 30–50 lx. For many years, the DLMO was determined mainly with the ‘gold standard’ GCMS technique for measuring melatonin in human plasma. However, new and improved RIAs now provide the requisite sensitivity and accuracy (specificity) for detecting the time that low daytime levels begin to increase in the evening: the lower the operational threshold for the DLMO, the more reliable it is as a phase marker.

Original languageEnglish (US)
Pages (from-to)79-83
Number of pages5
Issue number1-2
StatePublished - Mar 19 1999



  • Bright light
  • Dim light melatonin onset
  • Endogenous circadian pacemaker
  • Melatonin
  • Melatonin GCMS assay
  • Melatonin RIA
  • Phase-advanced disorders
  • Phase-delayed disorders

ASJC Scopus subject areas

  • Neurology
  • Developmental Neuroscience
  • Cellular and Molecular Neuroscience

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